SUMMARY

The following is a summary that highlights information contained in this joint proxy statement/prospectus. This summary may not contain all of the information that is important to you. For a more complete description of the merger agreement and the transactions contemplated by the merger agreement, IES and MISCOR encourage you to read carefully this entire joint proxy statement/prospectus, including the attached Annexes and the Risk Factors beginning on page 30.

The Companies

Integrated Electrical Services, Inc.

IES is a leading provider of infrastructure services to the residential, commercial and industrial industries as well as for data centers and other mission critical environments. IES operates primarily in the electrical infrastructure markets, with a corporate focus on expanding into other markets through strategic acquisitions or investments. Originally established as IES in 1997, it is a Delaware corporation providing services from 56 domestic locations as of March 31, 2013. IES is headquartered in Houston, Texas, and maintains an executive office in Greenwich, Connecticut. IES’ operations are organized into three principal business segments, based upon the nature of its current products and services:

IES common stock is traded on the NASDAQ under the symbol “IESC.” IES’ principal executive offices are located at 5433 Westheimer Road, Suite 500, Houston, Texas 77056, and its telephone number is (713) 860-1500.

MISCOR Group, Ltd.

MISCOR is a provider of maintenance and repair services including engine parts and components to industrial services and rail services. MISCOR began operations in July 2000 with the purchase of the operating assets of an electric motor and magnet shop in South Bend, Indiana. Through acquisitions and internal growth, MISCOR expanded the nature of its operations as well as its geographic presence, which now includes locations in Indiana, Alabama, Ohio, West Virginia and California.

MISCOR operates primarily in two business segments:

MISCOR common stock is traded in the OTCQB under the symbol “MIGL.” MISCOR’s principal executive offices are located at 800 Nave Road, SE, Massillon, Ohio 44646, and its telephone number is (330) 830-3500.

IES Subsidiary Holdings, Inc.

Merger Sub is a direct, wholly-owned subsidiary of IES. Merger Sub, a Delaware corporation, was formed on March 6, 2013, solely for the purpose of effecting the merger. Merger Sub has not conducted any business operations other than activities incidental to its formation and in connection with the transactions contemplated by the merger agreement.

The principal executive offices of Merger Sub are located at 5433 Westheimer Road, Suite 500, Houston, Texas 77056, and its telephone number is (713) 860-1500.

The Merger Agreement (see page 138)

IES and MISCOR have agreed to combine their businesses pursuant to the merger agreement described in this joint proxy statement/prospectus, subject to the requisite stockholder approvals and other conditions. Under the terms of the merger agreement, MISCOR will merge with and into Merger Sub, with Merger Sub surviving the merger as the “surviving corporation,” a direct, wholly-owned subsidiary of IES. The merger agreement, as amended, is attached as Annex A to this joint proxy statement/prospectus and is incorporated by reference herein. IES and MISCOR encourage you to read the merger agreement in its entirety because it is the legal document that governs the merger.

Risk Factors (see page 30)

There are risks associated with the merger and the operations of IES and IES common stock after the merger. These risks are more fully described in “Risk Factors,” beginning on page 30.

Risk Factors Relating to the Merger

Among the risk factors relating to the merger are the following:

Risk Factors Relating to IES Following the Merger

Among the risk factors relating to IES after the merger are the following:

Risk Factors Relating to IES Common Stock Following the Merger

Among the risk factors relating to IES common stock after the merger are the following:

Merger Consideration (see page 138)

At the effective time of the merger, each outstanding share of MISCOR common stock (other than shares held by MISCOR shareholders who do not vote in favor of the adoption of the merger agreement and who are entitled to and properly demand appraisal rights in accordance with Indiana law (“Dissenting Shares”) and shares to be canceled pursuant to the terms of the merger agreement) will be converted into the right to receive merger consideration comprised of, at the election of the holder, either: (1) a per share dollar amount (the “Cash Consideration”), which amount shall not be less than $1.415 (the “Minimum Cash Consideration”), equal to the quotient obtained by dividing (x) the difference between $24.0 million and the amount of MISCOR’s Net Debt (as defined in the merger agreement) and (y) the number of shares of MISCOR common stock outstanding as of the fifteenth business day prior to the closing date (the “Merger Consideration Determination Date”), including shares issuable upon the exercise of outstanding options and warrants; or (2) a number of shares of IES common stock (the “Stock Consideration”) equal to a fraction (the “Exchange Ratio”), the numerator of which is the Cash Consideration and the denominator of which is the volume-weighted average of the sale prices per share of IES common stock (the “VWAP”) for the 60 consecutive trading days ending with the Merger Consideration Determination Date (the “IES Common Stock Value”); provided, however, that if the IES Common Stock Value is less than $4.024 per share or greater than $6.036 per share (the “VWAP Collar”), then the IES Common Stock Value will be $4.024 per share or $6.036 per share, respectively. Notwithstanding the foregoing, the aggregate Cash Consideration to be paid in connection with the merger shall not exceed a threshold, as described in the merger agreement (the “Maximum Cash Amount”), equal to the product obtained by multiplying (x) the Cash Consideration by (y) 50% of the number of shares of MISCOR common stock outstanding immediately prior to the effective time of the merger.

If the Merger Consideration Determination Date had occurred on July 24, 2013, it is estimated that each MISCOR shareholder would have the right to receive, subject to the terms of the merger agreement, at his or her election, either $1.48 in cash or 0.311 shares of IES common stock for each share of MISCOR common stock issued and outstanding, subject to the Maximum Cash Amount, based on the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, which assumptions will not be definitively determined until the Merger Consideration Determination Date. See Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2 for further discussion of these assumptions and a sensitivity analysis related to the potential consideration that may be received by MISCOR shareholders. The actual value of the consideration and the number of shares of IES common stock to be issued may differ from this example, given that these amounts will not be determined until the Merger Consideration Determination Date has passed and MISCOR shareholders have made their elections.

The formula for calculation of the merger consideration was designed to effect a fixed enterprise value for MISCOR of approximately $24 million, but to provide for adjustment of the purchase price to reflect MISCOR’s Net Debt at a time as close as possible to the closing date (because of the uncertainty in MISCOR’s projected debt levels due to its ongoing pay-down of debt). This formula benefits MISCOR shareholders by providing for higher total consideration in the event that MISCOR generates cash and pays down debt prior to closing. Pursuant to the merger agreement, MISCOR does not have a right to terminate the transaction if the market price of IES common stock falls to a value such that the per share consideration to be received by MISCOR

shareholders electing to receive Stock Consideration could be valued at less than $1.415, which is the minimum per share consideration to be received by MISCOR shareholders electing to receive Cash Consideration.

The inclusion of both cash and stock components of the merger consideration reflects the intent of IES management to balance the following objectives: preserving available liquidity at IES for financial flexibility; meeting internal liquidity requirements and those under IES’ credit facility; limiting dilution of IES’ existing stockholders; and offering MISCOR shareholders the opportunity to continue to participate in the future potential growth of MISCOR’s business and IES through their ownership of IES common stock. Based on these objectives, if the merger consideration had been limited to only Cash Consideration, IES management and the IES board of directors may not have been able to recommend a purchase of MISCOR that would require utilization of approximately $24 million in available liquidity. IES management also determined that it would be in the best interest of IES and its stockholders to limit the cash component of the merger consideration to the Maximum Cash Amount in order to manage liquidity at IES within the constraints noted above and provide certainty as to the maximum liquidity impact of the transaction on IES. Further, IES management considered that it would be in the best interest of MISCOR’s shareholders to limit the cash component of the merger consideration to the Maximum Cash Amount, in order to meet the criteria for treatment of the consideration as non-taxable to MISCOR shareholders for U.S. federal income tax purposes.

The following chart illustrates the relative value of Stock Consideration to Cash Consideration at varying VWAP values and at two different levels of Cash Consideration: (i) $1.48 per share, which is the estimated Cash Consideration as of July 24, 2013, based on the pro forma assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, which assumptions will not be definitively determined until the Merger Consideration Determination Date, and (ii) $1.415 per share, which is the Minimum Cash Consideration as provided in the merger agreement. For purposes of calculating the value of the Stock Consideration, it is assumed that the market price of IES common stock is equal to the VWAP. The market price of IES common stock may be more or less than the VWAP on the Merger Consideration Determination Date or the closing date of the transaction. Please see “—Variables Impacting the Amount of Merger Consideration” beginning on page 16 and “Risk Factors Relating to the Merger—The estimated per share Cash Consideration and Stock Consideration are based on certain estimates, judgments and assumptions that may change or prove to be incorrect” on page 31. The highlighted rows represent the VWAP values that are within the VWAP Collar.

Per Share Value of Stock Consideration v. Cash Consideration

The following chart utilizes the values illustrated in the chart above to show the value of the Stock Consideration as a percentage of the Cash Consideration.

Value of Stock Consideration as a Percentage of Cash Consideration

The preceding charts assumes valuation of per share consideration based upon a range of potential VWAP values at the Merger Consideration Determination Date. However, the market value of IES common stock may fluctuate between the Merger Consideration Determination date and the date of receipt of the Stock Consideration by MISCOR shareholders in the merger. The “pro forma” consideration values are based upon the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, including Cash Consideration of $1.48 per share, which assumptions will not be definitively determined until the Merger Consideration Determination Date. The highlighted rows represent the VWAP values that fall within the VWAP Collar.

The following graph illustrates IES’ stock performance since July 1, 2012 and VWAP performance since July 31, 2012.

Impact of Maximum Cash Amount

Each MISCOR shareholder will have the right to elect to receive all Cash Consideration, all Stock Consideration or a mix of Cash Consideration and Stock Consideration, subject to the Maximum Cash Amount, which is equal to approximately 50% of the total consideration to be received by MISCOR shareholders in the merger. If the aggregate amount of cash that would be paid upon conversion of the shares of MISCOR common stock for which MISCOR shareholders elect to receive Cash Consideration collectively, including, in the event that the IES Common Stock Value is less than $4.024, all shares of MISCOR common stock for which a valid election was not made (the “Cash Election Shares”), is greater than the Maximum Cash Amount, then the exchange agent shall select from among the Cash Election Shares, by a pro rata selection process, a sufficient number of shares (the “Stock Designation Shares”) such that the aggregate amount of cash that will be paid in the merger in respect of the Cash Election Shares that are not Stock Designation Shares equals as closely as practicable the Maximum Cash Amount, and the Stock Designation Shares shall be converted into the right to receive the Stock Consideration. Any MISCOR shareholder that does not make a valid election with respect to such holder’s MISCOR common stock shall be deemed to have elected to receive the Stock Consideration; provided, however, that if the IES Common Stock Value is less than $4.024, then such shareholder will be deemed to have elected to receive, and will be paid, subject to the Maximum Cash Amount, Cash Consideration. If the Merger Consideration Determination Date had occurred on July 24, 2013, the default election would have been Stock Consideration, based on the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, which assumptions will not be definitively determined until the Merger Consideration Determination Date.

If the aggregate amount of cash that would be paid upon conversion of the Cash Election Shares is greater than the Maximum Cash Amount, then the determination of which Cash Election Shares will be designated as Stock Designation Shares will be made by the exchange agent. The determination of the number of Stock Designation Shares to be allocated to each MISCOR shareholder will be made by multiplying the number of Cash Election Shares held by such MISCOR shareholder by a fraction, the numerator of which is (x) the number of all Cash Election Shares less 50% of the number of shares of MISCOR common stock outstanding immediately prior to the effective time of the merger, and the denominator of which is (y) the number of all Cash Election Shares.

As of July 24, 2013, Tontine and Mr. Martell owned 49.9% and 23.4% of the outstanding MISCOR common stock, respectively. Mr. Martell and representatives of Tontine have each engaged in non-binding discussions with representatives of MISCOR and IES regarding their intentions to elect to receive Stock Consideration and/or Cash Consideration in the merger. If Tontine’s and Mr. Martell’s elections are consistent with their non-binding indications, it would result in the election of sufficient Stock Consideration to avoid triggering the Maximum Cash Amount and thereby limiting the Cash Consideration available to unaffiliated MISCOR shareholders in the merger.

Tontine has indicated that it intends to elect to receive Stock Consideration for 100% of its shares of MISCOR common stock, subject to the exercise of fiduciary duties in the management of its funds and other factors. Similarly, Mr. Martell has indicated that he intends to elect to receive Stock Consideration for not less than 500,000 shares and not more than 1,500,000 shares of MISCOR common stock, depending on certain factors and considerations. Based on these non-binding indications, it is anticipated that, at a minimum, 54% of the shares of MISCOR common stock outstanding as of July 24, 2013 will elect to receive Stock Consideration in the merger.

The non-binding indications provided by Tontine and Mr. Martell impacted the assumption made in the pro forma financial statements that MISCOR shareholders holding approximately 75% of MISCOR’s issued and outstanding common stock (as of the Merger Consideration Determination Date) will elect to receive Stock Consideration and that MISCOR shareholders holding approximately 25% of MISCOR’s issued and outstanding common stock (as of such date) will elect to receive Cash Consideration. A sensitivity analysis related to this assumption is also provided in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2.

If the Merger Consideration Determination Date had occurred on July 24, 2013, it is estimated that the Maximum Cash Amount would have been approximately $8.7 million and that holders of up to approximately 5.9 million shares of MISCOR common stock could have elected to, and would have, received Cash Consideration in the merger, in each case based on the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, which assumptions will not be definitively determined until the Merger Consideration Determination Date. Based on these assumptions, if the Merger Consideration Determination Date had occurred on July 24, 2013, the aggregate amount of cash that would be paid upon conversion of the Cash Election Shares would be less than the Maximum Cash Amount, and no shares of MISCOR common stock for which a cash election was made would have received shares of IES common stock in lieu of cash.

Assumptions Underlying Calculations of Estimated Merger Consideration and Estimated Ownership of IES Common Stock Following Completion of the Merger

The calculation of estimated per share Cash Consideration and Stock Consideration, as of July 24, 2013, and the calculations of estimated ownership of IES common stock following completion of the merger are based on the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, which assumptions will not be definitively determined until the Merger Consideration Determination Date. These assumptions include the following:

In making these calculations, it has also been assumed that MISCOR shareholders holding approximately 75% of MISCOR’s issued and outstanding common stock (as of the Merger Consideration Determination Date) will elect to receive Stock Consideration and that MISCOR shareholders holding approximately 25% of MISCOR’s issued and outstanding common stock (as of such date) will elect to receive Cash Consideration. This is IES management’s best estimate at this time, which is based, in part, on the expectation (based on Tontine’s and Mr. Martell’s non-binding election indications) that Tontine will elect to receive Stock Consideration for 100% of its MISCOR common stock (or 49.9% of MISCOR’s outstanding common stock as of July 24, 2013) and Mr. Martell will elect to receive Stock Consideration for between 18.3% and 54.8% of his MISCOR common stock (or between 4.2% and 12.7% of MISCOR’s outstanding common stock as of July 24, 2013). Please see Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2 for further discussion of, and a sensitivity analysis related to, this assumption. Please also see “Impact of Maximum Cash Amount” beginning on page 14.

All assumptions are based on IES management’s best estimates at this time. Actual amounts may vary from these estimates based on, among other factors, (i) the number of MISCOR equity units for which Cash Consideration is elected and the number of MISCOR equity units for which Stock Consideration is elected, (ii) the IES Common Stock Value, (iii) if the IES Common Stock Value is outside of the VWAP Collar on the Consideration Determination Date, (iv) the market price of IES common stock on the closing date, and (v) fluctuations in MISCOR’s Net Debt prior to the Merger Consideration Determination Date. Please see Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2 for sensitivity disclosures related to certain of the assumptions described above.

Variables Impacting the Amount of Merger Consideration

As described above, the Cash Consideration and Stock Consideration to be received by MISCOR shareholders in the merger are subject to numerous variables, which are subject to fluctuation and will not be determined until the Merger Consideration Determination Date. The most significant of these variables are the amount of MISCOR’s Net Debt and the market price of IES common stock.

The market price of IES common stock could be impacted by numerous factors (as more fully described in “Risk Factors” beginning on page 30) and could decline if, among other things, any amount of IES common stock is sold. On February 21, 2013, pursuant to a registration rights agreement with Tontine, IES filed a shelf registration statement (as amended, the “Shelf Registration Statement”) to register all of Tontine’s shares of IES common stock. The Shelf Registration Statement was declared effective on June 18, 2013. For so long as it remains effective, Tontine will have the ability to resell any or all of the shares of IES common stock included in the Shelf Registration Statement from time to time in one or more offerings, as described in the Shelf Registration Statement and in any prospectus supplement filed in connection with an offering pursuant to the Shelf Registration Statement. IES has received no indication from Tontine that it intends to resell any securities pursuant to the Shelf Registration Statement prior to the closing of the merger, nor has Tontine made any such sale pursuant to the Shelf Registration Statement to date. For additional information on the Shelf Registration Statement, please see “IES Management’s Discussion and Analysis of Financial Condition and Results of Operations—Controlling Shareholder” beginning on page 190.

Should Tontine sell or otherwise dispose of all or a portion of its position in IES, a change in ownership of IES could occur. A change in ownership, as defined by Internal Revenue Code Section 382, could reduce the availability of IES’ net operating losses (“NOLs”) for federal and state income tax purposes. For additional information on IES’ NOL position, please see “Business of IES – Net Operating Loss Carry Forward” beginning on page 161, “IES Management’s Discussion and Analysis of Financial Condition and Results of Operations—Controlling Shareholder” beginning on page 190 and “Risk Factors Relating to IES’ Business and Operations—Availability of net operating losses may be reduced by a change in ownership” on page 39.

Preferred Stock Purchase Rights (see page 128)

On January 24, 2013, the IES board of directors declared a dividend of one preferred share purchase right for each outstanding share of IES common stock. The dividend was payable to the stockholders of record as of the close of business on February 19, 2013. Each preferred share purchase right represents a right to purchase one one-thousandth of a share of Series A Junior Participating Preferred Stock, par value $0.01 per share, of IES at a price of $20.00. Each share of IES common stock issued as Stock Consideration in the merger will include one preferred share purchase right.

Treatment of MISCOR Stock Options and Other Equity Awards (see page 143)

The treatment of stock options and restricted share awards outstanding under the MISCOR stock plans is discussed under the heading “The Merger Agreement—Treatment of MISCOR Stock Options and Other Equity Awards” beginning on page 143.

Recommendation of the IES Board of Directors (see page 67)

The IES board of directors, based on the recommendation of the disinterested members of the IES board of directors, (1) has determined that the merger agreement and the transactions contemplated by the merger agreement, including the issuance of shares of IES common stock in the merger, are advisable and in the best interests of IES and its stockholders, (2) has approved the merger and the merger agreement and (3) recommends that the stockholders of IES approve the issuance of shares of IES common stock in the merger. No stockholder vote is required for Merger Sub to adopt the merger agreement and consummate the transactions contemplated by the merger agreement, other than the vote of IES acting as the sole stockholder of Merger Sub.

The IES board of directors recommends that IES stockholders vote FOR the issuance of shares of IES common stock in the merger and FOR the adjournment or postponement of the IES Meeting to a later date or dates, if necessary or appropriate, to solicit additional proxies. In considering the recommendation of the IES board of directors, you should be aware that certain directors of IES have personal interests that may motivate them to support the merger.

Recommendation of the MISCOR Board of Directors (see page 62)

The special committee of the MISCOR board of directors (the “Special Committee”) and the MISCOR board of directors, (1) have determined that the merger agreement, the merger and the other transactions contemplated by the merger agreement are advisable and in the best interests of MISCOR and its shareholders, as well as its stakeholders, in accordance with the requirements of Indiana law, (2) have approved the merger agreement, the merger and the other transactions contemplated thereby, (3) have directed that the merger agreement be submitted for adoption by the MISCOR shareholders at the MISCOR Meeting and (4) hereby recommend that the MISCOR shareholders adopt the merger agreement.

The MISCOR board of directors hereby recommends that MISCOR shareholders vote FOR the adoption of the merger agreement, FOR the approval of the merger-related named executive officer compensation proposal and FOR the adjournment or postponement of the MISCOR Meeting to a later date or dates, if necessary or appropriate,

to solicit additional proxies. In considering the recommendation of the MISCOR board of directors, you should be aware that certain directors and executive officers of MISCOR have interests in the transactions contemplated by the merger agreement that may be different from, or in addition to, the interests of MISCOR shareholders generally.

Opinions of Financial Advisers (see pages 74 and 83)

Opinion of IES’ Financial Adviser

In connection with the merger, IES’ financial advisor, Stifel, Nicolaus & Company, Incorporated (“Stifel”) delivered a written opinion, dated March 11, 2013, to the IES board of directors as to the fairness, as of such date, from a financial point of view, to IES, of the merger consideration to be paid by IES to holders of MISCOR common stock in the merger pursuant to the merger agreement. The full text of Stifel’s written opinion, dated March 11, 2013, which describes the assumptions made, procedures followed, matters considered and limitations on the review undertaken, is attached as Annex B to this joint proxy statement/prospectus. Stifel received a fee of $250,000 upon the delivery of its opinion that is not contingent upon consummation of the merger. IES has also agreed to reimburse Stifel for certain of its expenses incurred in connection with Stifel’s engagement. Stifel will not receive any payment or compensation contingent upon the successful consummation of the merger. Stifel’s opinion was provided for the information of, and directed to, the IES board of directors for its information and assistance in connection with its consideration of the financial terms of the merger. Stifel’s opinion does not constitute a recommendation to the IES board of directors as to how the board of directors should vote on the merger or to any holder of IES or MISCOR common stock as to how any such holder should vote at any stockholders’ meeting at which the merger is considered, or whether or not any stockholder of IES should enter into a voting, stockholders’, or affiliates’ agreement with respect to the merger, or exercise any dissenters’ or appraisal rights that may be available to such stockholder or whether or to what extent a shareholder of MISCOR should elect to receive Cash Consideration or Stock Consideration. In addition, Stifel’s opinion does not compare the relative merits of the merger with any other alternative transactions or business strategies which may have been available to IES and does not address the underlying business decision of the IES board of directors or IES to proceed with or effect the merger. Stifel was not requested to, and did not, explore alternatives to the merger or solicit the interest of any other parties in pursuing transactions with IES.

Opinion of MISCOR’s Financial Adviser

In connection with the merger, MISCOR’s financial adviser, Western Reserve Partners LLC (“Western Reserve”) delivered a written opinion dated March 13, 2013, to the MISCOR board of directors as to the fairness to MISCOR shareholders other than IES and its affiliates (including Tontine), from a financial point of view and as of the date of the opinion, of the Minimum Cash Consideration to be paid by IES to such stockholders in the merger of $1.415 per share assuming that all of MISCOR’s shareholders elect to receive Cash Consideration.

The full text of Western Reserve’s written opinion, dated March 13, 2013, is attached as Annex C to this joint proxy statement/prospectus. Holders of MISCOR common stock are encouraged to read the opinion carefully in its entirety for a description of the procedures followed, assumptions made, matters considered and limitations on the scope of the review undertaken. Western Reserve received an aggregate fee of $221,496.50 for its services in connection with the proposed merger, a portion of which was paid throughout Western Reserve’s engagement as a retainer, and a portion of which was payable upon the rendering of its opinion. MISCOR has also agreed to reimburse Western Reserve for certain of its expenses incurred in connection with Western Reserve’s engagement. Western Reserve will not receive any payment or compensation contingent upon the successful consummation of the merger. Western Reserve’s opinion was provided to the MISCOR board of directors in connection with its evaluation of the consideration to be paid by IES to the holders of MISCOR common shares in the merger, does not address any other aspect of the proposed merger and does not constitute a recommendation to any holder of MISCOR common stock as to how the shareholder should vote or act on any matter relating to the merger.

Western Reserve’s opinion does not address the fairness to MISCOR shareholders of the Stock Consideration or a mix of Cash Consideration and Stock Consideration.

MISCOR Request for Opinion on Minimum Cash Consideration

Prior to the MISCOR board of directors voting on the transaction, MISCOR sought an opinion from Western Reserve. Western Reserve offered its opinion as to the fairness to MISCOR shareholders (other than IES and its affiliates) of the Minimum Cash Consideration, because MISCOR and Western Reserve understood that:

Ownership of IES After the Merger

If the Merger Consideration Determination Date had occurred on July 24, 2013, current IES stockholders would own in the aggregate approximately 94.8% of the combined corporation (including the shares of IES common stock to be issued to Tontine in the merger), based on the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, which assumptions will not be definitively determined until the Merger Consideration Determination Date, and assuming 15,105,846 shares of IES common stock outstanding immediately prior to the effective time of the merger. This amount may vary

depending on the actual number of shares of MISCOR common stock outstanding at the effective time of the merger, the actual Exchange Ratio, and the number of MISCOR shareholders who elect to receive Stock Consideration in the merger. Consequently, IES stockholders, as a general matter, will have less influence over the management and policies of IES than they currently exercise over the management and policies of IES. See Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2 for further discussion of these assumptions and a sensitivity analysis related to the potential consideration that may be received by MISCOR shareholders.

Share Ownership of Directors and Executive Officers of IES

As of the close of business on July 24, 2013, the latest practicable date prior to the record date, the directors and executive officers of IES and their affiliates beneficially owned and were entitled to vote approximately 406,916 shares of IES common stock, collectively representing approximately 2.69% of the shares of IES common stock outstanding and entitled to vote on that date. The issuance of shares of IES common stock in the merger must be approved by the affirmative vote of the holders of a majority of the votes cast at the IES Meeting, including the votes cast by the directors and officers of IES and their affiliates. The shares of IES common stock owned by the directors and executive officers of IES will also be considered in determining satisfaction of the IES Minority Approval condition.

Share Ownership of Directors and Executive Officers of MISCOR

As of the close of business on July 24, 2013, the latest practicable date prior to the record date, the directors and executive officers of MISCOR and their affiliates beneficially owned and were entitled to vote approximately 2,764,800 shares of MISCOR common stock (excluding the 67,000 outstanding options held by MISCOR’s directors and executive officers), collectively representing approximately 23.7% of the MISCOR common stock outstanding and entitled to vote on that date. The adoption of the merger agreement must be approved by the affirmative vote of the holders of a majority of the outstanding MISCOR common stock entitled to vote as of the record date, including the votes cast by the directors and officers of MISCOR and their affiliates. The MISCOR common stock owned by the directors and executive officers of MISCOR, other than Mr. Martell, will also be considered in determining satisfaction of the MISCOR Minority Approval condition.

Interests of Directors, Executive Officers and Affiliates of MISCOR in the Merger (see page 92)

In considering the recommendation of the MISCOR board of directors with respect to the merger agreement, MISCOR shareholders should be aware that certain members of the MISCOR board of directors and certain of MISCOR’s executive officers have interests in the transactions contemplated by the merger agreement that may be different from, or in addition to, the interests of MISCOR shareholders generally. These interests may include, among other things, the following:

It is anticipated, based on current discussions between the companies, that all members of MISCOR’s management team, including the executive officers of MISCOR, will continue with the surviving corporation following completion of the merger. While IES has not entered, and does not anticipate entering, into new employment agreements with any of MISCOR’s executive officers, the surviving corporation will assume Mr. Moore’s employment agreement following completion of the merger. After the merger, MISCOR’s then-existing management team will be employed by the surviving corporation, which will be a wholly-owned subsidiary of IES. It is anticipated that Michael Moore and Marc Valentin, each of whom currently serves as an executive officer of MISCOR, will also serve as executive officers of Merger Sub, which we refer to as the “surviving corporation,” following completion of the merger.

The MISCOR board of directors was aware of these interests and considered them, among other matters, in making its recommendation. See “Special Factors—Recommendation of the MISCOR Board of Directors and Its Reasons for the Merger,” beginning on page 62.

The table below presents information regarding the maximum estimated value of total merger consideration that each director, executive officer and affiliate of MISCOR will receive as a result of the merger, based on the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2, including the assumptions that Mr. Martell will elect Stock Consideration for 1,000,000 shares of his MISCOR common stock (the mid-point of his non-binding indication), Tontine will elect 100% Stock Consideration, and the directors and executive officers of MISCOR (other than Mr. Martell) will elect 50% Cash Consideration and 50% Stock Consideration. The table below assumes that the Merger Consideration Determination Date occurred on July 24, 2013. The actual value of the consideration and the number of shares of IES common stock to be issued may differ from this example, given that these amounts will not be determined until the Merger Consideration Determination Date has passed and MISCOR shareholders have made their elections. For additional information, please see “Special Factors—Interests of Directors and Executive Officers of MISCOR in the Merger—Restricted Stock and Stock Options” beginning on page 92.

If the Merger Consideration Determination Date had occurred on July 24, 2013, MISCOR’s directors and executive officers would own in the aggregate approximately 1.8% of the shares of IES common stock outstanding after the merger and Tontine and MISCOR’s directors and executive officers would together own in the aggregate approximately 60.0% of the shares of IES common stock outstanding after the merger (including the shares of IES common stock owned by Tontine prior to the merger), in each case, based on the assumptions described above and assuming 15,105,846 shares of IES common stock outstanding immediately prior to the effective time of the merger. The transaction is not expected to result in Mr. Martell becoming a 5% beneficial owner of IES.

Interests of Tontine in IES and MISCOR (see pages 96 and 97)

Share Ownership

As of July 24, 2013, Tontine owned approximately 49.9% of MISCOR’s outstanding common shares and approximately 56.7% of the outstanding shares of IES common stock.

Board and Management Representation

MISCOR Board Representation. MISCOR has granted Tontine the right to appoint members to the MISCOR board of directors as follows:

The MISCOR board of directors currently consists of four directors. MISCOR has also agreed that, for as long as Tontine has the right to appoint directors, the number of directors on the MISCOR board of directors will not exceed seven. Tontine has not appointed a director to the MISCOR board of directors.

In addition to Tontine’s right to appoint directors, MISCOR also granted Tontine the right to have a representative attend all meetings of the MISCOR board of directors, the boards of directors of MISCOR’s subsidiaries and their respective committees, for so long as Tontine or its affiliates continue to hold at least 10% of MISCOR’s outstanding common shares. Mr. Lindstrom periodically attended the MISCOR board meetings as a representative of Tontine, while he was employed at Tontine; however, neither Mr. Lindstrom nor any representative of Tontine has attended a MISCOR board meeting since August 10, 2011.

Mr. Martell has granted Tontine an irrevocable proxy to vote his shares of MISCOR common stock for the election to the MISCOR board of directors of Tontine’s designees.

IES Board Representation. David B. Gendell, who is the brother of Jeffrey Gendell (the founder and managing member of Tontine) and an employee of Tontine Associates, L.L.C., has served as a member of the IES board of directors since February 2012. Mr. Gendell was not appointed to the IES board of directors pursuant to or in connection with any agreement or understanding between IES and Tonine.

Interests of Tontine Following Completion of the Merger

Following completion of the merger, Tontine is expected to own an estimated 58.0% of the outstanding shares of IES common stock, based on the assumptions described in Note 3 to the Unaudited Pro Forma Condensed Combined Financial Statements beginning on page F-2.

In connection with the merger, Tontine will not receive any rights with respect to representation on the IES board of directors or within IES management. Following completion of the merger, each of MISCOR’s executive officers and directors will resign as directors and officers of MISCOR, pursuant to the terms of the merger agreement, and Tontine’s right to appoint members to the MISCOR board of directors and its board observer rights with respect to meetings of the MISCOR board of directors will terminate.

Listing of Shares of IES Common Stock; Removal and Deregistration of Shares of MISCOR Common Stock (see page 101)

IES will use its reasonable best efforts to notify the NASDAQ of the shares of IES common stock to be issued in the merger prior to the effective time of the merger in accordance with the NASDAQ listing rules. Under the merger agreement, MISCOR is required to cooperate with IES with respect to such notice to facilitate providing notification as required pursuant to NASDAQ rules. Approval of the listing on the NASDAQ of the shares of IES common stock to be issued in the merger is not required pursuant to the NASDAQ listing rules and therefore is not a condition to each party’s obligation to complete the merger. If the merger is completed, the MISCOR common stock will be removed from OTCQB and deregistered under the Exchange Act.

Appraisal Rights in the Merger (see page 154)

MISCOR shareholders who wish to seek appraisal of their shares are urged to seek the advice of counsel with respect to the availability of dissenters’ rights.

A MISCOR shareholder who delivers to MISCOR, before the shareholders vote is taken at the MISCOR Meeting, written notice of the shareholder’s intent to demand payment in cash for shares owned if the merger is effectuated and does not vote the shareholder’s shares in favor of the merger will not receive the merger consideration. The shareholder will instead be entitled to assert dissenters’ rights and seek an appraisal of its shares, unless the shareholder fails to take the steps prescribed by Chapter 44 of the IBCL to perfect such shareholder’s dissenters’ rights. Upon consummation of the merger and receipt of a payment demand, former MISCOR shareholders who have complied with all statutory requirements will be paid the fair value of the shares as of the time immediately before the merger. The full text of Chapter 44 of the IBCL is attached as Annex D to this joint proxy statement/prospectus.

Holders of IES common stock will not have the right to seek appraisal of the fair value of their shares of IES common stock.

Conditions to the Completion of the Merger (see page 144)

A number of conditions must be satisfied or waived, where legally permissible, before the proposed merger can be consummated. These include, among others:

Neither IES nor MISCOR can assure you when or if all or any of the conditions to the merger will be either satisfied or waived or whether the merger will occur as intended.

Pursuant to the terms of the merger agreement, each of IES and MISCOR may waive in writing in whole or in part any or all of such party’s conditions to completion of the merger, provided that those requirements that are a condition to both IES’ and MISCOR’s completion of the merger, including the IES Minority Approval and MISCOR Minority Approval, must be waived in writing by both parties. In the event that either the IES Minority Approval or the MISCOR Minority Approval is not received, IES and MISCOR may determine, based on the facts as they then exist, that waiver of such conditions is in the best interest of IES, MISCOR and their respective stockholders. Neither IES nor MISCOR intends to re-solicit stockholder approval in the event that either party waives a material condition to completion of the merger, except as may be required by the merger agreement with respect to MISCOR’s receipt of an opinion of its tax counsel, as described under “Material U.S. Federal Income Tax Consequences of the Merger—Material U.S. Federal Income Tax Consequences of the Merger to MISCOR Shareholders” beginning on page 134. As of July 24, 2013, neither IES nor MISCOR anticipated waiving any condition to its obligation to complete the merger.

No Solicitation (see page 147)

The merger agreement prohibits MISCOR from soliciting alternative transactions other than during the limited period that began on the date of the merger agreement and ended at 12:01 a.m. (EST) on April 13, 2013 (the “Solicitation Period”). Following the Solicitation Period, MISCOR is not permitted to:

Notwithstanding the foregoing, and subject to certain additional limitations and conditions, before receipt of the requisite approval by its stockholders, MISCOR may engage in negotiations with a third party making an unsolicited, bona fide, written acquisition proposal, provided that:

In addition, subject to certain additional limitations and conditions, before receipt of the requisite approval by its stockholders, the board of directors of MISCOR may withdraw its recommendation or declaration of advisability of the merger agreement if the board of directors determines in good faith that a failure to change its recommendation is reasonably likely to be inconsistent with its fiduciary duties to the MISCOR shareholders, subject to payment of the termination fees set forth in the merger agreement.

Termination of the Merger Agreement (see page 151)

The merger agreement may be terminated and the merger may be abandoned at any time prior to the effective time of the merger by mutual written consent of IES and MISCOR. The merger agreement may be terminated by written notice at any time prior to the effective time of the merger in any of the following ways:

See “The Merger Agreement—Termination of the Merger Agreement and Termination Fees,” beginning on page    .

Termination Fees and Expenses (see page 152)

In the event of a termination of the merger agreement under the following circumstances, MISCOR will be required to pay IES a termination fee in the amount of $250,000:

If, within 365 days of a termination of the merger agreement as a result of MISCOR’s failure to receive shareholder approval of the merger or MISCOR Minority Approval, MISCOR consummates an alternative transaction with any person or entity that submitted an alternative transaction prior to termination of the merger agreement (regardless of whether such alternative transaction was the basis for termination of the merger agreement), MISCOR will be required to pay IES an additional fee of $500,000 (which will result in a combined termination fee of $750,000).

In the event of a termination of the merger agreement as a result of the failure of the IES stockholders to approve the issuance of shares of IES common stock in the merger or the failure of IES to receive the IES Minority Approval, IES will be required to reimburse MISCOR for its out-of-pocket and documented expenses incurred in connection with the merger in an amount not to exceed $250,000.

Material U.S. Federal Income Tax Consequences (see page 134)

The merger is intended to qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code (the “Code”) for U.S. federal income tax purposes, and the closing is conditioned upon the receipt by MISCOR of an opinion from Ulmer & Berne LLP, counsel to MISCOR, to the effect that the merger so qualifies. This discussion of U.S. federal income tax consequences assumes that the merger will be consummated as described in the merger agreement and this joint proxy statement/prospectus. In the opinion of Ulmer & Berne LLP, the merger will be treated for U.S. federal income tax purposes as a reorganization qualifying under the provisions of Section 368(a) of the Code. If the merger qualifies as such a reorganization, the material U.S. federal income tax consequences of the merger to U.S. holders of MISCOR common stock will be as follows:

For further information, please refer to “Material U.S. Federal Income Tax Consequences of the Merger.” The United States federal income tax consequences described above may not apply to all holders of MISCOR common stock. Your tax consequences will depend on your individual situation. Accordingly, we strongly urge you to consult your tax advisor for a full understanding of the particular tax consequences of the merger to you.

Accounting Treatment (see page 100)

In accordance with accounting principles generally accepted in the United States of America (“GAAP”), the merger will be accounted for as an acquisition of a business. IES will record net tangible and identifiable intangible assets acquired and liabilities assumed from MISCOR at their respective fair values at the date of the completion of the merger. Any excess of the purchase price, which will equal the market value at the date of the completion of the merger, of the IES common stock and cash issued as consideration for the merger over the net fair value of such assets and liabilities will be recorded as goodwill.