I live very close to the the geographic center of the US and have a 6.5KW system attached to a 6KW grid tie inverter. I have a gas furnace and water heater. Over the last winter (read heating season) I produced about 1200 kwh's that I didn't use and sold back to my utility company at an astonishingly low $0.015 per KWH (my utility won't pay me retail for pushing power back onto the grid, only the "saved fuel cost"). I figure that if I would have used these same 1200 kwh's to power a 1500w electric space heater properly positioned in my house for a few carefully chosen hours a day, it would have offset a little more than 6,000,000 BTU's of heating over the course of the winter, which would have lowered my monthly natural gas bill substantially more than the $18 I got paid for my excess production. So I'd say it's not a fools errand to try to do this if you find yourself overproducing in the winter in some cases, depending on how your utility handles net metering.