Heating Model S?

[ahirbe]

So just an off the wall thought, but according to some calculations from a Kman video the heater in the Model S uses 342Wh when set at 74 degrees and 6.4KWh when set to hi...if you used one of those small car heaters (12V) for your feet (that is usually the only cold part for me) they only use 150Wh...is this a correct assumption that using the smaller heater for feet is better than the cars heater?

 

[boaterva]

Technically, they use W, and when you use them for an h, you get...

I'm not sure you want to use a 150 W heater, as that would be about 12 Amps of power (assume 12 Volts). I'd not plug that into the power port (cigarette lighter, to us old folks...) but you could wire it up somehow.

But theoretically, yes, you're correct. And using the seat heater and a small foot heater is more efficient that using the whole cabin heater, that's one basic step in increasing range. Not sure I've seen this one before (foot heater...).

Personally, I'd use the seat heater, the steering wheel heater (if it was that cold), and a lot of socks for my feet.

 

[Rocky_H]

This seems like someone is not thinking through the whole issue by just comparing the power levels.
This is basically the same as saying: "This hair dryer uses this much power. My furnace uses much more power. So I could save energy by using the hair dryer to heat my house instead of the furnace."

Well, no, it's consuming less power because it's producing far less heat! You would have to run the hair dryer tons more to get the same warmth. The built-in heater of the car, and the 12V heater you're talking about are both using a resistive wire to do a straight resistive conversion of electrical energy to heat energy at 100% efficiency. There is no difference at the heating coil. Granted, the only difference is that the 12V heater is producing the heat right there inside the car in the footwell, so it's not having to transport/blow the heated air anywhere. The car heater is elsewhere and blows the hot air through ducts into the car, so there is a little loss from warming the walls of the ducts, but that would probably be a pretty small effect. But no--there's not going to be an energy difference to get the same amount of warmth.

 

[boaterva]

This seems like someone is not thinking through the whole issue by just comparing the power levels.
This is basically the same as saying: "This hair dryer uses this much power. My furnace uses much more power. So I could save energy by using the hair dryer to heat my house instead of the furnace."

Well, no, it's consuming less power because it's producing far less heat! You would have to run the hair dryer tons more to get the same warmth. The built-in heater of the car, and the 12V heater you're talking about are both using a resistive wire to do a straight resistive conversion of electrical energy to heat energy at 100% efficiency. There is no difference at the heating coil. Granted, the only difference is that the 12V heater is producing the heat right there inside the car in the footwell, so it's not having to transport/blow the heated air anywhere. The car heater is elsewhere and blows the hot air through ducts into the car, so there is a little loss from warming the walls of the ducts, but that would probably be a pretty small effect. But no--there's not going to be an energy difference to get the same amount of warmth.

Right, and thinking of it, seriously, a better approach for a long trip maximizing battery usage (range) would be to use the seats and battery powered (plug in) socks. If you are prone to cold feet, that, the seat heaters, and the steering wheel (if you have it) heater would really do the job at about 25% the 'cost' of running the whole car heater. (Depending on how many bodies, of course...)