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EV TOU Charging

CWFLY

Member
May 9, 2018
70
66
San Diego
My power company has both TOU and EV-TOU. There's a big difference, and it is important to consider the difference.

The TOU (Time of Use) simply means that the rates vary by time of day. Whenever possible, charge your car during the lowest TOU rate (e.g. super-off-peak might be midnight to 6am). We all know that.

But what gets lost in a lot of the discussion is that some of the Rate Plans have a baseline (or tier). A baseline is a monthly goal that is set by the power company for you. If you go above this goal, they add a hefty increase to your rate. For instance: My normal rate is 23 cents for the first 300 kWh, and then 43 cents for each kWh above 300. In other words, the rate almost doubles. There's 20 cent penalty on every kWh after reaching your baseline.
(FWIW, I almost never exceeded my 300 kWh baseline... until I bought an EV).

So now, if I stay on my original plan, almost every kWh for my car is costing me 43 cents. Why?... because my house uses the entire baseline and everything beyond that (car charging) is at 43 cents.

Time to explore this EV-TOU thing!!!

In San Diego (SDG&E), the EV-TOU rates appear to be slightly higher than the normal TOU rates. So then why would anybody choose the EV plan?... Simple... because the EV rates increase or eliminate the Baseline threshold. No 20 cent penalty.

That means I charge my car for 23 cents per kWh (instead of 43 cents).

Always consider the baseline or tier when choosing a Rate Plan. The cost difference can be significant.
 
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liuping

Active Member
Jul 23, 2013
2,243
923
San Diego
Most power companies have an online what-if evaluator that can take your previous tiered usage and apply a TOU estimate to see if it makes sense for you....
The problem is you need almost a years worth of data to really evaluate (due to season rate and solar product changes) using the SDG&E tools. That's a long time to be paying $0.43 vs $0.28 per kWh for charging.

Also, it does not take into account changes you can make. i.e. running pool pumps, washing machines, dishwasher, etc. only during off peak time, instead during the 4-9pm peak rate period.
 
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SDM3

Member
Feb 28, 2018
12
1
SD
and if you have solar, the choice becomes easier
From your experience, what is that clearer choice? I have solar and when I called SDG&E to ask about the best plan, they said it doesn't matter since I rarely owe on my bill. However, seems to me that I could get a larger credit but they assured me that this is not possible since all $/kWh for credit purposes are the same regardless of the plan. Would be great to understand how others are managing.
 

insaneoctane

Active Member
Apr 6, 2016
3,765
9,054
Southern California
From your experience, what is that clearer choice? I have solar and when I called SDG&E to ask about the best plan, they said it doesn't matter since I rarely owe on my bill. However, seems to me that I could get a larger credit but they assured me that this is not possible since all $/kWh for credit purposes are the same regardless of the plan. Would be great to understand how others are managing.
Solar almost always does very well in TOU. Because of the TOU leveraging I get with SCE, while I'm a net consumer of electricity, I still have had over $500 credit at the end of my true up period. Like the stock market.....Buy low, sell high! My Model 3 will help fix my $500 credit problem, though ;)
 

Daniel in SD

Well-Known Member
Jan 25, 2018
7,069
10,535
San Diego
Solar almost always does very well in TOU. Because of the TOU leveraging I get with SCE, while I'm a net consumer of electricity, I still have had over $500 credit at the end of my true up period. Like the stock market.....Buy low, sell high! My Model 3 will help fix my $500 credit problem, though ;)
Not true anymore in San Diego. The dreaded "duck curve" is starting to occur and peak demand has moved to the evening. SDG&E TOU peak hours are now 4-9pm. I would guess that SCE will do the same soon as more people get solar.
 

CWFLY

Member
May 9, 2018
70
66
San Diego
Wish I could do solar... Condo association makes it almost impossible.

My car/home energy ratio is about 50/50. Avoiding peak times is key. As more and more cars go EV, the peak time may shift towards weekday nights.
 
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insaneoctane

Active Member
Apr 6, 2016
3,765
9,054
Southern California
Not true anymore in San Diego. The dreaded "duck curve" is starting to occur and peak demand has moved to the evening. SDG&E TOU peak hours are now 4-9pm. I would guess that SCE will do the same soon as more people get solar.
It's awful. Doing solar is the right thing, and then if people do it they reduce the financial incentives! It reminds me of the aftermath of the water drought in California. The water companies beat their drums to reduce consumption, reduce, reduce....conserve, conserve, conserve. Over the course of years people did just that, they reduced and conserved....to the point that the water company started to lose significant revenue because it was based on how much water you used....with all the conservation they didn't take in enough money to support their "needs" and decided to raise rates to fix the problem. Thanks!
 
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mrsandman

Member
Jan 21, 2016
123
171
Los Angeles
SCE has about 5 different TOU plans, some of which are tiered and some aren’t. Last month was the first full month of having the model 3 and I was running on a TOU with a tiered rate. Our bill was about $225. This month we switched to another TOU plan without a tiered rate and made some other adjustments with electrical consumption. The new plan is much cheaper starting at 10pm until 8am, so I adjusted our pool pump, light schedules and the charging of the M3 and am eager to see the impact.
 

SageBrush

REJECT Fascism
May 7, 2015
12,592
16,791
New Mexico
So now, if I stay on my original plan, almost every kWh for my car is costing me 43 cents. Why?... because my house uses the entire baseline and everything beyond that (car charging) is at 43 cents.
If I am reading the TOU tariff chart correctly a more accurate statement is that above 130% of baseline a surcharge of 20.4 cents a kWh is added to your consumption during that TOU period.

I looked at the TOU2-EV tariff chart

Screenshot 2018-05-30 at 5.45.59 PM.png

I think you are agreeing to a minimum 33 cents per kWh rate according to the bottom row in the table.
 
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Daniel in SD

Well-Known Member
Jan 25, 2018
7,069
10,535
San Diego
It's awful. Doing solar is the right thing, and then if people do it they reduce the financial incentives! It reminds me of the aftermath of the water drought in California. The water companies beat their drums to reduce consumption, reduce, reduce....conserve, conserve, conserve. Over the course of years people did just that, they reduced and conserved....to the point that the water company started to lose significant revenue because it was based on how much water you used....with all the conservation they didn't take in enough money to support their "needs" and decided to raise rates to fix the problem. Thanks!
Natural gas power only costs a few cents a kWh and water is free. Most of the cost is maintaining the infrastructure. The way the power industry is regulated in CA is going to lead to a death spiral of rising rates.
Don't get me wrong, I've got solar and am loving my $5 power bills but it's completely unsustainable.
 

remlemasi

Member
May 30, 2018
357
295
SoCal
Solar almost always does very well in TOU. Because of the TOU leveraging I get with SCE, while I'm a net consumer of electricity, I still have had over $500 credit at the end of my true up period. Like the stock market.....Buy low, sell high! My Model 3 will help fix my $500 credit problem, though ;)

SCE has about 5 different TOU plans, some of which are tiered and some aren’t. Last month was the first full month of having the model 3 and I was running on a TOU with a tiered rate. Our bill was about $225. This month we switched to another TOU plan without a tiered rate and made some other adjustments with electrical consumption. The new plan is much cheaper starting at 10pm until 8am, so I adjusted our pool pump, light schedules and the charging of the M3 and am eager to see the impact.

Yep! We have a BMW i3 and use TOU leveraging. Last year, we consumed a net total of around 2000 kWh and still received a $40 check at true-up (although it includes the roughly $60 in climate credits and doesn't take into account the 4 months of $10 minimum bills I had to pay, so it's really net $0 out-of-pocket all said and done).

I designed my parents' system similarly and to great success! They have two EVs, Chevy Spark and BMW i3, and by the end of their annual true-up, they will have consumed a net total of around 5700 kWh and will pay only around $20 or so for that benefit for the entire year (again, $60 in climate credits applied).

Here's the kicker: we both have TINY 8 panel systems A 2.52kW system for us (1400sqft house) and 2.64kW system for them (2400sqft house).

Both households are almost always within the monthly baseline, whether positive or negative, which ensures the 4c/kWh effective rate applies for nighttime charging ( [12c - 4c]/ kWh, TOU-D-A).

Absolutely wild how much energy we are getting for next to nothing just by leveraging TOU rates!

Because of this, I always encourage people considering solar NOT to oversize their system; ROI drops way down.

That being said, I acknowledge that rate plans can always change and no one knows what they will look like in 10 years. If you sleep better at night and have the extra funds, by all means, oversize away!
 

Daniel in SD

Well-Known Member
Jan 25, 2018
7,069
10,535
San Diego
Because of this, I always encourage people considering solar NOT to oversize their system; ROI drops way down.
In San Diego they have moved TOU peak period to 4-9pm and all new solar customers are required to have a TOU plan after 5 years so you actually need to oversize your system to get to $0 bills. I expect other power companies will do the same. It's still worth it since power here is so crazy expensive.
 

SageBrush

REJECT Fascism
May 7, 2015
12,592
16,791
New Mexico
It's still worth it since power here is so crazy expensive.
... and PV can be so cheap.

Rather simply, if the rate during sunshine hours is half the 4pm - 9pm rate, you only need to generate twice your peak rate consumption.
Since PV amortizes out to under 5 cents a kWh for most people the peak rate hours can work out to as cheap as 10 cents a kWh. The only real gotcha is if the utility limits your PV array size to match annual consumption.
 

remlemasi

Member
May 30, 2018
357
295
SoCal
In San Diego they have moved TOU peak period to 4-9pm and all new solar customers are required to have a TOU plan after 5 years so you actually need to oversize your system to get to $0 bills. I expect other power companies will do the same. It's still worth it since power here is so crazy expensive.

Yep, I did say that things are always changing!

SCE is currently 2pm-8pm, which isn't that far off from 9pm, but it really depends on your household patterns, kids, stay at home / work from home, A/C usage, etc, etc, etc.

I really should say, do your homework and run those spreadsheets to ensure you are getting the best ROI now and cross your fingers for the future. Or you can just oversize and be done with it :)
 

SageBrush

REJECT Fascism
May 7, 2015
12,592
16,791
New Mexico
This is an interesting 'what if' analysis by a solar company using customer data
SDG&E’s New Time of Use Rates: How Solar Savings Are Changing, Backed by Data

Relevant to the OP, the excess charges related to consumption over 130% of baseline are not in play when PV is placed. And of course this analysis does not include any consumption behavior adjustments in the future such as moving load to non peak hours.

'Tis a game, and for now PV owners are one step ahead of the utility.
 
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