The electric heater wide open (only permitted by the comfort setting) can draw 6.5kW. In addition, the fan can draw up to 200W or so IIRC, and under some circumstances (high relative humidity,) the car will run the A/C in parallel with the heater to defrost. I'm not positive of the max A/C draw - it's somewhere in the 3kW neighborhood.If it's cold with four people in the car with snowy clothes/shoes that are melting and you have the climate settings on comfort and 76 degrees with the defog and defrost on, the climate system can use more than 3kW. I don't know what the exact number is, but one Volt advisor who posts here mentioned "more than 7kW". Even with "fan only" in cold temperatures I never saw more than ~33m range, so I think there are other parasitic loads in cold weather. Those loads have an impact on optimum speed for range, probably pushing it up into the 45 to 50 MPH range.