Several people pointed out that my long extension cord run might be causing losses, so I figured I'd test it because I have the technology. (though no one asked *why* I'm doing that - answer at the end of thread)

Yes, I own two kill-a-watt meters - so what? https://twitter.com/ElephantEating/status/1352329709762326610

Between the garage and the car's charger thing I have 200 ft of extension cord. So I took 2 kill-a-watt meters and put one on each side of the 200 ft of cord (one between garage plug and start of cord, other between end of cord and charger thing).

So, basically, one measures how much energy went into the extension cord and the other measures how much came out the other side. I let the car charge for a few hours and found that 2.54 kWh went in and 2.24 came out, so a loss of 12%.

Side note: I checked before I went outside that the two meters were reading things the same way by plugging them through each other when connected to a small space heater (and found that they observed the same voltage/current/energy), so it shouldn't be measurement error.

Let's think about two things now: how much does that 12% loss cost me and how much heat is it throwing?

Cost: We don't drive a lot - maybe I'd expect 5000 electric miles per year. I don't yet have data on my efficiency, but 3 miles/kWh seems like a reasonable number from others.

So, rough numbers: I might send 1700 kWhs into the car per year. At a 12% loss, I would lose 200 kWh to the cord. In our area, that is about $25 of electricity.

But (and I'll get back to this later), I won't be using the extension for most of the year.

So, as far as heat goes, I know that the car charges at around 1 kW (or a bit less) with this setup. If there are 12% losses, that means that the rate of energy loss is about 120 W. That's the heat of two 60W bulbs (which do throw some heat!), but spread over 200 ft of cord.

A person is also around 60W, so the losses in the cord (which manifest as heat) would be about the same as the heat given off by two people (the surface of a person is cooler than a 60W bulb, but we have a lot more surface area...)

Ok, finally: Why do I have this silly long extension cord running all the way from the garage? Just put the car at the garage, right? Well, we get a lot of snow in the winter and I don't like to pay people to plow it or use power tools for this, so I shovel it.

And our driveway is very long (200 ft of cord), so in the winter we park our only car down near the sidewalk so that I only need to shovel the small portion between the back of the car and the street. Thus, by April, the extension will disappear and the 12% losses with it.

PS: I want to remind everyone that the big benefit of my garbage can/extension cord charging setup is that 100% of the material was sitting around in my house/garage already. It was not carefully optimized (and won't be in the future!), though it has a certain savage logic.

PPS: the cord does not seem particularly effective at melting snow, so there goes that plan....