Saw this on my SB homepage under "Most Popular Ways to Earn." YMMV since Arcadia may not be available in all areas in the US.
Linked to my electric company account painlessly and 1000 SB are pending for 32 days. Arcadia is essentially a middle man who receives your utility bill; Arcadia passes along your utility bill to you (so your rates/charges are the same) and you pay Arcadia, who then pays your utility co. partially by using their solar/wind energy. So you get bonus warm fuzzies for being an environmentally conscious slickdealer.
The account is totally free if you opt to have 50% renewable energy; upgrading to 100% renewable power costs extra. There don't seem to be any hidden service fees, taxes, or fees to pay with credit cards.
I didn't grab a screenshot or URL before doing the offer and it's now disappeared from my SB page since I've completed it. Attaching my pending SB confirmation as proof.