What I do is switch off my whole house heat and just use an electric space
heater in the room I am using (close door).

With solar electric, there is a thing called "net metering" where you sell
electricity to the electric company during the day, then buy electricity at
night. This eliminates the need for batteries.

See following links or search google.com for "net metering" or "grid tie"
using quotes...

http://www.xantrex.com/web/id/1024/solutions.asp

http://www.google.com/search?hl=en&q=%22net+metering%22