Comment by rootusrootus
5 hours ago
A lot of people quoting low rates are also just referring to their off-peak rate. This is pretty common in EV discussions. It's not exactly a fair argument there, either, because the flip side of having an off-peak rate is that the on-peak rate is usually quite a lot higher. So the true effective rate is a bit higher, somewhere in the middle depending on usage pattern.
It's easy to have your EV only charge off-peak, though. It's just a setting.
My point is that the tradeoff to get off-peak pricing is that on-peak is way, way more expensive. So you can charge the EV off-peak to maximize the savings, but everything else you do during on-peak time costs way more.
Using myself as an example:
I adjust my A/C to run outside of 5pm-9pm (peak) if at all possible, we try to avoid pointless high-draw usage during that same window, and both of our EVs hold off charging until after 9pm.
My rate from 5pm-9pm is 0.43/kWh. My rate after 9pm is 0.09/kWh. The flat rate alternative, if I did not want to worry about time of day, would be 0.21/kWh. These prices are all-in, including transmission and distribution/whatever.
It would be dishonest to say that my EVs only cost me 0.09/kWh to operate, which on it's face is a claim to paying over 50% less. In reality, time of day pricing typically saves me somewhere between 10% and 15% in an average month compared with flat rate.
If you leave the EV charging out of your consumption, does a time of day plan still save you money on the remaining usage? Or does it cost you? If it saves you money, then it would make sense to be on a ToD plan regardless of EV charging. Which means it makes sense to consider your additional EV draw as costing the marginal off-peak rate. Essentially the EV load has the valuable property of being dispatchable.
You can do the same thought experiment with say a dehumidifier in your basement. It can easily be off during peak usage and still accomplish its job, so its cost of electricity is also the marginal off-peak rate.
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Fair point.
I guess it depends on if you would be using ToU otherwise.
It looks like about 50% of Californians use ToU plans, but the number is only 10% nation-wide.