Anyone know anything about solar Power?

[MarkCO]

Here is a general information site: http://www.combustionportal.org/hydronicheaters.cfm

If you already have a wood stove inside, you can add a kit like this: https://www.northerntool.com/shop/to...2034_200362034

If not, you can buy a wood stove with a hydronic loop in the back. They run in the $1000 to $3000 range for small units, which will be less than the batteries. If you are only heating the hot tub, you will want a way to keep from delivering water that is too hot which will take a throttling valve on a cartridge circulator pump. The ones I use are a bit more money since they are used to heat 4,000 to 8,000 square foot homes You can always go cheap and build yourself a barrel stove from a kit and drop one of those hydronic loops in it as well.

http://www.acehardware.com/product/i...hoCzckQAvD_BwE

Here is a guy who did just that: https://diybarrelstoveoutdoorfurnace...tdoor-furnace/

[Lurch]

Thanks for all the info.