Ideal Power Inc.

As filed with the Securities and Exchange Commission on March 27, 2026

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORMS-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

IDEAL POWER INC.

(Exact name of registrant as specified in its charter)

5508 Highway 290 West, Suite 120

Austin, Texas,78735

(512)264-1542

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

David Somo

President and Chief Executive Officer

Ideal Power Inc.

5508 Highway 290 West, Suite 120

Austin, Texas, 78735

(512) 264-1542

(Name, address, including zip code, and telephone number, including area code, of agent for service)

With Copies to:

Ned A. Prusse

Perkins Coie LLP

1900 Sixteenth Street, Suite 1400

Denver, Colorado 80202

(303) 291-2300

**Approximate date of commencement of proposed sale to the public:**From time to time, after the effective date of this registration statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box: ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the U.S. Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION DATED MARCH 27, 2026

PRELIMINARY PROSPECTUS

Up to 631,332 Shares of Common Stock Issuable Upon Exercise of Pre-Funded Warrants

This prospectus covers potential resale by certain selling securityholder (the “Selling Securityholder”) identified herein of 631,332 shares of our Common Stock, par value $0.001 per share (“Common Stock”) issuable upon the exercise of pre-funded warrants at an exercise price of approximately $0.001 per share (“Pre-Funded Warrants”).

We are registering the shares on behalf of the Selling Securityholder to be offered and sold by it from time to time. We are not selling any securities under this prospectus and will not receive any proceeds from the sale of Common Stock by the Selling Securityholder pursuant to this prospectus. The Selling Securityholder may offer and sell such shares to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods or any other method permitted by law. See “Plan of Distribution” for more information about how the Selling Securityholder may sell or otherwise dispose of such shares. Our registration of these shares does not mean that the Selling Securityholder will offer or sell any shares of our Common Stock.

Our Common Stock is currently listed on The Nasdaq Capital Market under the symbol “IPWR”. On March 26, 2026, the last reported sale price of our Common Stock was $3.11. The applicable prospectus supplement, if any, will contain information, where applicable, as to any other listing, if any, on The Nasdaq Capital Market or any securities market or other securities exchange of the securities covered by the prospectus supplement. Prospective purchasers of our securities are urged to obtain current information as to the market prices of our securities, where applicable.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

We may amend or supplement this prospectus from time to time by filing amendments or supplements as required. We urge you to read the entire prospectus, any amendments or supplements, any free writing prospectuses, and any documents incorporated by reference carefully before you make your investment decision.

Investing in our securities involves a high degree of risk. See“Risk Factors”** beginning on page** 8 of this prospectus for a discussion of certain risks that you should consider in connection with an investment in our securities.

The date of this prospectus is , 2026.