Yanno... if you had thermal solar cells and a near perfectly insulated basement storage tank that covered 1000 square feet and was a full 8' tall that would get you 500,000 pounds of water. Every 2 degrees of water you could store it above say 68° means a million stored BTUs.
If you could get the water up over 100°, that's a ΔT OF 32° (assuming 68° indoor air temp) OR 16 million BTUs. I have a pretty average house and used 66 million BTUs, roughly 4x as much as what that could store. I could see it easily doing half the season!
...but just imagine if it were to ever freeze in a prolonged power outage. Yikes!
