I'm currently a renter (and a landlord), and I'd definitely pay more rent for a home with solar. I might hesitate with a lease that billed me based on kwh, however. I'm not entirely sure why, especially because DH and I tend to have lower-than-average electric bills. It just feels weird. So if I thought about it, maybe I'd go for that. But paying $100 more in rent would be a no brainer. (We live in a very HCOLA, and our rent in an fairly far-our suburb is $3600, so $100 would be a much smaller % than on a $900 place.)
I wonder if you could offer 2 options, like $950 rent or $875 rent and then being billed XX per kwh. I've seen leases that are $3500 with included lawn care, or $3600. (I don't recall if that was the actual differential.) So you could do something similar with the electric bill, and either their use from your panels is included in the higher rent, or they are billed for it.