Geothermal might be doable here, but you'll need a pro to tell you for sure. A three ton geothermal might need 8-10 gpm, sometimes around the clock. Pumping from the ground might well cost as much as running the heatpump itself, if you have to lift water very far. Open loop systems such as these can be marginal (I have one.)

Is the lake large? If it's big enough and doesn't freeze solid it might be possible to circulate lake water. This would be especially attractive if your home and the lake are roughly level to each other. In that case you would trench below the frost line from the house to the lake and lay pipe running both ways, and your main pumping issues would be overcoming friction rather than lifting- an order of magnitude cheaper. It may be possible to lay coils in the lake, in which case it is a closed loop system, and that could be very worthwhile.

Again, it'll take an on-site inspection by a qualified professional to tell you for sure, but it's at least worth checking into. I hope you'll look into it and report back here to satisfy my curiosity!

Good luck,

Mark

If your lake is deep enough, you might be able to use pond loops, lots of people do. That way you would have a closed system, no dumping. I have a closed loop system, but the loops are vertical. I am very happy with my geo system.

Check out the www.geoexchange.org forums to research pond loops, or geo in general. Someone who already had a geo system - an open loop system for his 2500 sq ft cape - told me about the site. It's where he learned about geothermal. I learned a lot there too, before buying my own system. It seems to be run by pros, but lots of homeowners like me use the forums also. Good luck!