The smallest Trane air handler/heater combination I looked at (https://www.trane.com/content/dam/Trane/Commercial/global/products-systems/equipment/unitary/spli

The smallest Trane air handler/heater combination I looked at (https://www.trane.com/content/dam/Trane/Commercial/global/products-systems/equipment/unitary/split-systems/Small%20Splits/Air%20Handlers/22-1897-1D-EN_08162017.pdf https://www.trane.com/content/dam/Trane/Commercial/global/pr...) is only around 6000-7000 watts; you'd want a 10kw generator and a Genrac portable would run you about $1000. Keep up with the maintenance; you'll probably want to try filling it with fuel, running it, and draining the fuel a couple of times a year. Note: this is just for heating; don't plug anything else into the generator while you're heating---the peak startup loads make generators sad. If you've got natural gas (uh, whoops) or propane, a whole-house generator would only be a few thousand more (not counting installation). (I've considered one, but we don't have either, which means either getting a propane tank and service or going with diesel, which has maintenance aspects.)