Hi all, I've heard rumors of boilers/water heaters that have built in pumps that use a stirling type engine, therefore using the heat from the boiler to drive the pump. I plan on building off the grid so every bit of electricity I can save would help. This is especially true since I want to heat over the winter when I'm not there and not have to worry about relying on batteries/solar to keep my heating going. Any help would be appreciated. Regards,