I guess I still don't know exactly how electricity works. I thought the kilowatt cost was associated with how long you drew power from 120v/15a. So I though 1 hour from a laptop was the same as 1 hour from a microwave, and the same for 1 hour from an EV. It makes sense that some devices would use less power.

Oooh, I see why you have some confusion about this, and it's not just you. We use a very convoluted and confusing unit for energy.

The official metric unit for energy is a Joule. But a Joule is really small, so electric companies don't want all of the numbers coming out in millions and billions, so they have created a different unit that is kind of formed from another one.

Watt or kilowatt is a unit for amounts of energy per time. So if you multiply that by time, you cancel out the denominator and get the energy amount, right? So a kilowatt is a rate of energy per time, multiply by hours, and you get kilowatt-hours, which is an amount of energy. So that may be where you were thinking cost was based on time used instead of amounts of energy.

So now here's how we apply this:

Your Tesla pulls 120 Volts x 12 Amps continuous = 1440 Watts

Your iPhone pulls 5 Volts x 2 Amps = 10 Watts. Compare the Watts, and it's not even 1% as much.

These are accurate rates of power for these kinds of devices: 1,440 Watts and 10 Watts. Let me convert those to kilowatts first:

1.44 kilowatts and 0.01 kilowatts

If you used each of those for 1 hour, you multiply by 1 and get 1.44 kWh and 0.01 kWh as the actual amounts of energy used. So you used them for the same amount of time, but one is drawing energy much faster, so it uses more total energy in that same time.

So yeah, the units on this stuff are kind of confusing and annoying, but that is why you do sometimes see people being nitpicky about making sure people are using the right units. kW is a rate of energy usage and kWh is the amount of energy.