Winter is hard on electric vehicles. Turn on the heat and it gets even harder. The electrical motor and inverter put off barely any heat compared to an internal combustion engine, so no free heat. Mine uses a set up like a hot water heater element immersed in antifreeze and the antifreeze is circulated through a normal heater core. I figured if the weak heater became a problem I'm sure I could figure something out. Well it became a problem and I think I figured it out. I decided that I would like lots of heat with little to no loss in range. A feat not even the newer heat pump heater cars can match. I'm looking at the Eberspacher diesel fired coolant heater. It puts off between 15,000 and 5,000 BTUs per hour. The leaf has a display for how much power is going to its electric heater. It usually draws between 1,000 and 5,000 watts, which is between 3,400 BTUs per hour and 17,000btu per hour. So the diesel coolant heater lines up pretty well with what the factory electric heater already does. I figured it will probably use around a gallon of diesel per month.