X0508 4 2025-12-05 0 0001805077 Eos Energy Enterprises, Inc. EOSE 0001833275 Stidolph Russell Monoki C/O ALTENERGY LLC 137 ROWAYTON AVENUE ROWAYTON CT 06853 1 0 0 0 0 Common Stock 2025-12-05 4 S 0 500000 14.99 D 2153272 I See footnote Common Stock 2025-12-08 4 S 0 29999 15.36 D 2123273 I See footnote Common Stock 2025-12-05 4 J 0 75000 0 D 2048273 I See footnote Common Stock 2025-12-05 4 J 0 75000 0 A 439355 D Common Stock 2025-12-05 4 G 0 60000 0 D 379355 D Common Stock 2025-12-05 4 G 0 15000 0 D 364355 D Common Stock 2025-12-08 4 M 0 30788 14.43 A 395143 D Common Stock 2025-12-08 4 F 0 30020 14.80 D 365123 D Common Stock 2025-12-08 4 S 0 768 14.80 D 364355 D Common Stock 2025-12-08 4 M 0 145018 1.18 A 509373 D Common Stock 2025-12-08 4 M 0 120633 2.32 A 630006 D Common Stock 2025-12-08 4 F 0 18793 14.89 D 611213 D Common Stock 2025-12-08 4 F 0 11491 14.89 D 599722 D Common Stock 2025-12-08 4 S 0 235367 14.89 D 364355 D Stock Option (Right to Buy) 14.43 2025-12-08 4 M 0 30788 0 D 2025-12-08 Common Stock 30788 0 D Stock Option (Right to Buy) 1.18 2025-12-08 4 M 0 145018 0 D 2027-05-19 Common Stock 145018 0 D Stock Option (Right to Buy) 2.32 2025-12-08 4 M 0 120633 0 D 2028-05-18 Common Stock 120633 0 D The shares reported in this Form 4 are shares of common stock in which Mr. Stidolph has a pecuniary interest in that are held directly by AltEnergy, LLC or AltEnergy Transmission, LLC. Mr. Stidolph is the managing director of AltEnergy, LLC and the managing member of AltEnergy Transmission, LLC and has voting and dispositive power with respect to the securities owned by AltEnergy, LLC and AltEnergy Transmission, LLC. Each of the Filing Persons disclaims beneficial ownership of the outstanding shares of common stock of the issuer reported herein except to the extent of its pecuniary interest therein. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $15.28 to $15.45, inclusive. The reporting person undertakes to provide the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth above. Represents the receipt, for no consideration, of an aggregate of 75,000 shares of Common Stock of the Issuer by AltEnergy pursuant to pro rata distribution by AltEnergy. Represents a charitable donation by the reporting person. Reflects the donation of common stock to a charitable donor advised fund. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions pursuant to a Cashless exercise / same-day sale at prices ranging from $14.68 to $15.16, inclusive. The reporting person undertakes to provide the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth above. On December 8, 2020 the reporting person was granted stock options to purchase 30,788 shares of common stock which vested on June 15, 2021. On May 19, 2022 the reporting person was granted stock options to purchase 145,018 shares of common stock which vested on May 19, 2023. On May 18, 2023 the reporting person was granted stock options to purchase 120,633 shares of common stock which vested on April 30, 2024. /s/ Michael Silberman as attorney-in-fact for Russell Stidolph 2025-12-08