There is no US Solar Department in the US government, so this official looking email is very likely a fraud, scam, or phishing scheme to steal your identity or add Trojan horse malware into your computer.
The offer I just got with the official looking graphic here is from somebody at the domain rseidemann.com, not from the US Government or any recognized utility in the USA.
More, rseidemann.com comes up as a non-existent domain in a Google search.
That tells me the creep who is emailing these notices is bogus, a fraudster, scammer, identity thief, etc.
Do not click any links in this fraudulent email from the U. S. Solar Department.
That includes the “unsubscribe” link.
Just delete the whole thing.
Bye bye, scammer.
See more scam alerts on the ecoxplorer Frauds & Scams page.