According to a LinkedIn post from Sedo’s Sr. Broker Dave Evanson, the SolarEnergy.com domain name was sold via Sedo for $175,000:
The domain name is currently registered to Sedo’s transfer service, so the buyer is unknown at this point in time. The domain name has been registered under Whois privacy, so the seller is also unknown.
In doing a cursory search on NameBio, I can see this is the largest publicly reported -Energy.com domain name sale. AlternativeEnergy.com sold for a little more than $50,000 back in 2006, CleanEnergy.com sold for $50,000 in 2011, and WindEnergy.com sold for just shy of $40,000 in 2019. I can also see it is the largest Solar-related publicly reported domain name sale by a wide margin.