Hallador Energy Company (NASDAQ: HNRG) raises ATM stock capacity to $100M

Rhea-AI Filing Summary

Hallador Energy Company is updating its at-the-market common stock program to permit sales of up to $100,000,000 of shares under an existing sales agreement with B. Riley Securities.

The company has already sold Common Stock for aggregate gross proceeds of approximately $50,000,000 under the prior prospectus, and this supplement increases the maximum aggregate gross sales price from $50,000,000 to $100,000,000, enabling up to an additional $50,000,000 of stock sales. The terms of the sales agreement and the offering mechanics remain unchanged, and the shares continue to trade on Nasdaq under the symbol HNRG.

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-273327

PROSPECTUS SUPPLEMENT

(To Prospectus dated November 29, 2023)

HALLADOR ENERGY COMPANY

Up to $100,000,000

Common Stock

This prospectus supplement amends and supplements the prospectus dated November 29, 2023, filed as a part of our registration statement on Form S-3 (File No. 333-273327), as amended by our prospectus supplement dated December 18, 2023 (the “Prior Prospectus”). This prospectus supplement should be read in conjunction with the Prior Prospectus, and is qualified by reference thereto, except to the extent that the information herein amends or supersedes the information contained in the Prior Prospectus. This prospectus supplement is not complete without, and may only be delivered or utilized in connection with, the Prior Prospectus, and any future amendments or supplements thereto.

We filed the Prior Prospectus to register the offer and sale of our common stock, par value $0.01 per share (“Common Stock”), from time to time pursuant to the terms of that certain At Market Issuance Sales Agreement (the “Sales Agreement”) between B. Riley Securities, Inc. and us (the “ATM Offering”).

As of the date hereof, we have sold all of the shares of our Common Stock covered by the Prior Prospectus for an aggregate gross sales proceeds of approximately $50,000,000. We are filing this prospectus supplement to amend the Prior Prospectus solely to increase the maximum aggregate gross sales price of our Common Stock that may be offered, issued and sold under the Sales Agreement from $50,000,000 (which has already been sold to date) to $100,000,000, which will enable us to sell up to an incremental $50,000,000 of our Common Stock from and after the date hereof under the Sales Agreement.

Except as modified by this prospectus supplement, the terms of the ATM Offering remain unchanged, and the Sales Agreement remains in full force and effect.

Our Common Stock is listed on The Nasdaq Capital Market (“Nasdaq”) under the symbol “HNRG.” On December 15, 2025, the last reported sale price of our Common Stock on Nasdaq was $21.21 per share.

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

B. Riley Securities

The date of this prospectus supplement is December 16, 2025.

FAQ

What change is Hallador Energy Company (HNRG) making to its stock offering?

Hallador Energy Company is increasing the maximum aggregate gross sales price of its at-the-market common stock program to $100,000,000 under its existing sales agreement.

How much stock has Hallador Energy Company (HNRG) already sold under the prior prospectus?

The company has already sold all the shares covered by the prior prospectus for aggregate gross sales proceeds of approximately $50,000,000.

How much additional Hallador Energy (HNRG) common stock can be sold after this supplement?

This update will enable Hallador Energy to sell up to an incremental $50,000,000 of its common stock from and after the date of the prospectus supplement.

Does the Hallador Energy (HNRG) at-the-market sales agreement with B. Riley change?

No. The prospectus supplement states that, except for the increased maximum aggregate amount, the terms of the at-the-market offering and the sales agreement with B. Riley Securities remain unchanged and in full force and effect.

On which exchange does Hallador Energy Company (HNRG) trade and what is its ticker?

Hallador Energy Company’s common stock is listed on the Nasdaq Capital Market under the symbol HNRG.

What recent market price is disclosed for Hallador Energy (HNRG) common stock?

The prospectus supplement notes that on December 15, 2025, the last reported sale price of Hallador Energy’s common stock on Nasdaq was $21.21 per share.