Current Events

I was curious about how much current the Prime draws when plugged into a Level 2 EVSE unit and running its heat pump in "pre-conditioning mode."

Using a Leviton model EVR-40 with a kWh meter at the panel. I took these photos this morning because I was curious to learn how much power the heat pump uses:



The top measurement shows that the electronics in the EVSE use about 3.6 watts. That appears to be the "vampire load" of the EVSE's electronics and holds true whether the EVSE is unplugged from the vehicle or plugged into the fully-charged vehicle.

When "pre-conditioning" was started, the load increased to 7.5 watts. And when charging, the load shoots up to 3582 watts!

I noticed, however, that the meter display of watts is inconsistent with its display of current (amps). Simple multiplication of 245 volts x .05 amps is 12.25 watts, not 3.6 watts as displayed. Similarly, 246 volts x 0.65 amps is 160 watts, not 7.5 watts as displayed.

Full charging mode is more consistent, showing 243 volts x 15.29 amps = 3864 watts which is within 5% of the 3682 watts displayed.

Even allowing for meter inaccuracy, the low pre-conditioning power consumption is pretty remarkable. I'm just not sure it's believable.

Now, admittedly, the ambient temperature was 58-degrees F at the time I took these measurements. But the Prime's climate-control cabin temperature was set to 72-degrees so the heat-pump was working to compensate for a 14-degree demand gradient.

I don't know enough about the design of heat-pumps to know whether the heat-pump would draw more current when the ambient temperature is lower. Or whether the power consumption is the same when running in cooling mode.

It would be interesting to have more accurate numbers so that I could get a reasonable sense of how many kWh the heat-pump uses while driving -- and therefore how much of the Prime's available battery charge it is using.