Off Peak charging advice

What are the off-peak hours?

If you're not home during a workday, and you use the car a lot, maybe it will work out for you, but my guess is not.

In general, these plans only work to your advantage if you have solar PV at your home so you can reduce or eliminate the on-peak charges. In most cases the bulk of the usage is on-peak if you don't have solar.

You need to find out your peak/off peak hours. Here in this part of California we have pretty long off peak hours.
Winter: 10pm to 4pm off peak
Summer: 10pm to 2 pm off peak

Let's see. 29.7% of the hours during the week are defined as peak.

If your usage stayed constant 24x7, then your blended rate would be 29.7% x .165 + 70.3% x .05 = .084 which is cheaper than your $.10 per kW/hr you now pay and you get to charge your car at the cheaper rate.

Let's assume a pretty bad case scenario where during the peak rate time, your usage is double that during the non peak time. So 2 kW would be consumed every hour during the peak hours for every 1 kW every hour in the non peak times. So your energy consumption would be (10/24 * 5 * 2)/7 = 59.5% at the expensive rate.

So, 59.5% x .165 + 40.5% x .05 = .118 per kW/hr. Which is more expensive.

That's all in the summer. In the winter, it's a good deal regardless of the peak/non peak consumption pattern assuming your regular rate is $.10 year round.

Now all this isn't factoring in the cheaper charging rate for the car. If you drive an average 12,000 miles per year, that's 1,000 miles per month at say 400 wh/mile (factoring in some charging inefficiency), that's an extra 400 kW/hr per month. So roughly 10% of your bill would be at .05 or .10 per kW/hr depending on which scenario.

So ... It's close to break even for the worst case scenario. Personally, I would switch rates now and see what it does to your bill. You can always switch back.

And given rates are going to keep rising, yes, a PV system makes sense...

Agree with above. I don't know if it was realized or mentioned - summer is only 4 months.

So you are only getting penalized for 4 months and then only 5 days a week.

I went to a TOU when I got an EV. Also at that time, I got solar and an energy monitor. Obviously solar changes the equation completely. But skipping that, I was able to throw nearly all my hot water heating to off peak. I have a heat pump and in the winter I save a much bigger amount that a/c would have cost (if I didn't have solar).

The hot water thing is pretty easy. Most tanks have 2 heaters. You set the lower one a little higher temp and put that on a timer. The upper one will still run if needed during peak but it mostly won't ever run.

Having NG changes this of course.

David_Cary said:

The hot water thing is pretty easy. Most tanks have 2 heaters. You set the lower one a little higher temp and put that on a timer. The upper one will still run if needed during peak but it mostly won't ever run.

Click to expand...

I installed a timer on the entire hot water heater that is energized 1am - 5am. I only have to override the timer when we have guests and its only a 50gal tank.

Intermatic EH40 240-Volt Electronic Water Heater Timer - Wall Timer Switches - Amazon.com