Exhibit 23.1

We consent to the incorporation by reference in the Registration Statement of iSun, Inc. (formerly The Peck Company Holdings, Inc.) on Form S-3 (File Nos. 333-233107, 333-233931 333-249429 and 333-251154) and Form S-8 (File No. 333-249714) of our report dated March 15, 2021, except for the effects of the restatement in Notes 1,2,11,14 and 18 which is June 10, 2021, with respect to our audits of the consolidated financial statements of iSun, Inc. (formerly The Peck Company Holdings, Inc.) as of December 31, 2020 and 2019 and for the two years in the period ended December 31, 2020, which report is included in this Annual Report on Form 10-K/A of iSun, Inc. (formerly The Peck Company Holdings, Inc.) for the year ended December 31, 2020.

/s/ Marcum llp

Marcum llp

New York, NY

June 10, 2021

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Dated: June 10, 2021

POWER OF ATTORNEY

The undersigned directors and officers of iSun, Inc., hereby constitute and appoint Jeffrey Peck and John Sullivan, and each of them, with full power to act without the other and with full power of substitution and resubstitution, our true and lawful attorneys-in-fact with full power to execute in our name and on behalf in the capacities indicated below, this annual report on Form 10-K and any and all amendments thereto and to file the same, with all exhibits thereto and other documents in connection therewith with the Securities and Exchange Commission, and hereby ratify and confirm all that such attorneys-in-fact, or any of them, or their substitutes shall lawfully do or cause to be done by virtue hereof.

In accordance with the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in such capacities and on the dates indicated.

Dated: June 10, 2021