Feature request to not charge from "shore power" with TOU rates

techmaven · Mar 3, 2015

In the light of Jerome's recent remarks about feature requests coming from owners that actually set Tesla's development priorities, I humbly submitted this feature request and I hope all of you with TOU rates do the same. I would like to be able to prevent the Model S from using shore power during they day for chargers on TOU rates:

At my house, I have a dedicated EV meter with time of use rates. Which means I almost never want to pay the highest day rate. I pay 3x during the day and the costs for just the little bit of usage during the day means that my electric bill is 30% peak day usage and 70% night super off peak usage in terms of actual cost even though the energy usage is vastly different.

I would like to be able to select the charger at my house and choose to have it almost never be used during the day. In other words, when I choose to turn on the climate controls, it doesn't use "shore power." Similarly, when I plug in at the end of the day, it starts using "shore power" sometimes to check the charger and/or power the climate controls. I want it to not do that. On the other hand, if I manually start charging, then it is free to use shore power during the day.

Also, I can't use smart preconditioning as a result since it uses shore power at 3x the rate.

AZbba · Mar 4, 2015

I'd also like to see a stop charging time option instead of having to manually adjust the charge % to keep it within the midnight-6am window (single charger). It's not that often but it does happen.

David_Cary · Mar 4, 2015

Absolutely agree.

I live with a TOU-D rate. What this means is I pay a monthly charge based on my largest peak usage (only during peak hours). So if I accidentally charge at 10kw for 15 minutes during the day, that is a $50 surcharge that month. Sure it is an uncommon rate plan but since it makes a lot of sense, I suspect we will see more of it in the future.

For this privilege, I pay $.05 at night and $.07 during the day. So $50 can double my bill.

My other issue is off peak in the winter includes 1-4 pm, so I really need a robust multipoint timer. Not much of an issue with my driving and an S but has been an issue with the Leaf (and will with my wife and the Leaf).

And if I'm really dreaming, we could get smart and charge (at a separate defined rate) based on sun exposure. This would really help when net metering goes away.

Danal · Mar 4, 2015

Tesla should offer this... until they do, how does HPWC/UMC and the car react to source power being off? Or more precisely, coming back on?

You could just turn the power off during the hours you want to ensure the car does not use it. Up to 30A, Intermatic makes a reasonably priced timer designed for 240V Water Heaters. A little over a hundred for the timer, plus the fee for an electrician. Beyond 30A/240V, timers get rare and expensive. A better deal would be a "contactor" (a big relay) and almost any timer. That might take a more sophisticated electrician as well. Maybe a few hundred? Hard to say. DIY, the "contactor/low current timer" route could actually be cheaper than the Intermatic.

Again, Tesla absolutely should offer this. Until they do, avoiding $50 mistakes might be worth a couple of hundred.

andrewket · Mar 4, 2015

I don't understand. Did you mean to say not pre-heat from shore power? I have TOU and use scheduled charging. When on, the car won't charge outside the start time (by more than 4 hours, I think) even if there is an interruption in current.

Edit: never mind, just now read the Techmaven's original post and I understand.

mibaro2 · Mar 4, 2015

AZbba said:
I'd also like to see a stop charging time option instead of having to manually adjust the charge % to keep it within the midnight-6am window (single charger). It's not that often but it does happen.

Would like to see this also.
And to select the time when the car uses shore power.
The only downfall I can see about setting the time when the car cannot use shore power is if it really cold, and the car needs to heat the battery to prevent permanent damage. I would allow the car to override my request to not use shore power in that instance.

Duckjybe · Mar 4, 2015

All this complexity to save yourself how much? I'll bet not much.

FlasherZ · Mar 4, 2015

Danal said:
You could just turn the power off during the hours you want to ensure the car does not use it. Up to 30A, Intermatic makes a reasonably priced timer designed for 240V Water Heaters. A little over a hundred for the timer, plus the fee for an electrician.

They actually make a 40A version:
Intermatic 40 Amp 208-277 Volt 24 Hour DPST Mechanical Time Switch with Outdoor Enclosure-T104RD89 - The Home Depot

A quick note about code here - because it's an appliance, it's not required to be rated for 50A per continuous load rules of the NEC. It's tested at 40A per UL standards.

At $70, plus an hour of an electrician's time, it's likely going to be less than 3 months' worth of overage charges if that's the path you want to take. That may be better for some specific cases instead of adding some additional bloat to the code, depending on how many people need it.

The Tesla works well with this. If the power is completely off to the EVSE, then it offers no pilot signal to the car; without a pilot signal the Tesla tells you to check the wall power source. When the power returns, the car begins charging within 5 minutes.

Zarwin · Mar 4, 2015

I have TOU that doesn't really increase the rate charge during peak but does have a rolling window concurrent use surcharge during peak hours. I would LOVE to be able to block off the peak window and have the car not charge in this window. Yes, right now the start timer does do just fine, but I still need to be careful for the end time. I screw up one time and start charging late, and the car keeps charging into the window for just 20 minutes, BAM, that's a $70 charge added to my bill for the month. Not kidding.

Edit:
And to address the issue of maintaining the battery in extreme hot/cold environments during peak times, perhaps an override setting that would allow only a 1kw draw when needed to keep the concurrent usage down. Probably getting too complex... I'd be very happy with a simple blackout range.

mknox · Mar 4, 2015

Duckjybe said:
All this complexity to save yourself how much? I'll bet not much.

Depends on the jurisdiction. Here in Ontario we have pretty lame TOU rates with not much differential between On and Off peak. Not the case everywhere.

I can envision the day when the EVSE equipment will be "smarter" and allow the homeowner and/or utility take some control over this. Here is a unit that works with NEST thermostats and the utility Rush Hour Rewards (a demand response program).

Cottonwood · Mar 4, 2015

FlasherZ said:
They actually make a 40A version:
Intermatic 40 Amp 208-277 Volt 24 Hour DPST Mechanical Time Switch with Outdoor Enclosure-T104RD89 - The Home Depot

A quick note about code here - because it's an appliance, it's not required to be rated for 50A per continuous load rules of the NEC. It's tested at 40A per UL standards.

At $70, plus an hour of an electrician's time, it's likely going to be less than 3 months' worth of overage charges if that's the path you want to take. That may be better for some specific cases instead of adding some additional bloat to the code, depending on how many people need it.

The Tesla works well with this. If the power is completely off to the EVSE, then it offers no pilot signal to the car; without a pilot signal the Tesla tells you to check the wall power source. When the power returns, the car begins charging within 5 minutes.

My utility offers a Power Line Carrier (PLC) that indicates when off-peak rates occur. They also sell relay, etc controls that use this PLC to switch things like my high efficiency hot water heaters on and off. My electrician took a dry contact output from one of these and used it to control a 50 Amp contactor that feeds a 14-50 in the garage. When I want to only charge off-peak, I just plug the UMC into that 14-50. Works great, and because the on/off peak times change between winter and summer, it means I don't have to remember to change any timer settings.

techmaven · Mar 4, 2015

My follow up to Tesla was to basically say, let the car choose how to best charge during the given time.

I have a HPWC that can charge up to 80A. Given that I pay 6 cents at super-off peak which is between 1 am and 4 am and 17 cents during the day, I would really rather have the car choose the best charge rate and time. I should just set the range I want in the morning and the car should choose the amperage and the timing during super-off peak. It should take into account ambient temperature, expected temperature in the morning, available charge rate, and pack temperature. Maybe it's better for the life of the battery pack to start slower... and maybe in the winter it should bias towards finishing at 4 am while in the summer at a higher rate, but in the summer, start earlier at a lower rate. Who knows... they have all the data. The coding isn't all that complex.

FlasherZ · Mar 4, 2015

Cottonwood said:
My utility offers a Power Line Carrier (PLC) that indicates when off-peak rates occur. They also sell relay, etc controls that use this PLC to switch things like my high efficiency hot water heaters on and off. My electrician took a dry contact output from one of these and used it to control a 50 Amp contactor that feeds a 14-50 in the garage. When I want to only charge off-peak, I just plug the UMC into that 14-50. Works great, and because the on/off peak times change between winter and summer, it means I don't have to remember to change any timer settings.

Great solution!

David99 · Mar 4, 2015

Duckjybe said:
All this complexity to save yourself how much? I'll bet not much.

I pay 11 ct at night vs 49 ct during the day. I charge an average of 50 kWh every night. That would be a price difference of $19 every day or $7,000 a year. I think it's worth it.

I think there are several ways charging could be improved. The car should be aware of TOU times and rates. Many have requested the car to figure out when to start charging on its own based on state of charge and when you want the car to ready in the morning. This would optimize battery temperature and battery life as it keeps it in lower state of charge longer.

I don't think there is one best charging method, but there should be a few more options to customize it to your needs. One the same note, I would really like to be able to adjust the charge current on the mobile app.

Duckjybe · Mar 5, 2015

David99 said:
I pay 11 ct at night vs 49 ct during the day. I charge an average of 50 kWh every night. That would be a price difference of $19 every day or $7,000 a year. I think it's worth it.

I think there are several ways charging could be improved. The car should be aware of TOU times and rates. Many have requested the car to figure out when to start charging on its own based on state of charge and when you want the car to ready in the morning. This would optimize battery temperature and battery life as it keeps it in lower state of charge longer.

I don't think there is one best charging method, but there should be a few more options to customize it to your needs. One the same note, I would really like to be able to adjust the charge current on the mobile app.

I took from the original post that Techmaven doesn't want the car to use shore power during the day for pre-conditioning and battery warming. There already is a timer on the car for scheduled charging and to prevent charging during high TOU rates. Is this not sufficient for preventing charging during high TOU? I am not sure how much power is used to pre-condition but at my TOU rates it sure wouldn't be much cost. At your rates there may be a potential savings.

mknox · Mar 5, 2015

Duckjybe said:
I am not sure how much power is used to pre-condition but at my TOU rates it sure wouldn't be much cost. At your rates there may be a potential savings.

As close as I can tell, pre-conditioning can use up to 12 kW of power (6 for cabin heat and 6 for pack heat), but usually less. My 20 amp 240 volt circuit delivering 16 amps to the car only delivers 3.8 kW so whenever I pre-condition while plugged in, I still lose some range.

David_Cary · Mar 6, 2015

But even if the total KWH is not much, for those of us with demand pricing, it can be a big issue. In NC, most recent solar customers have demand pricing. To have a 20 minute oops every month can negate the financial savings of a 6 kw system.

Ask me how I know??

I only save about $60 a month averaged over the year. It was a $6k net system so not a terrible payback. But if demand gets you regularly - ie a preconditioning hit - then you lose your savings. Not a huge real financial hit - but a psych one particularly when it negates your solar system.

Electricity rates are unbelievably variable - a combination of government regulation, quasi monopoly and geographic resources. Demand charges are rational and the rational mind would think they will grow in popularity. Tesla should plan for it as the biggest single draw in almost any house that has one.

mibaro2 · Mar 6, 2015

I'm thinking that eventually there will be a "Timer" tab on the console. In that tab, you can put your electricity rates for a 24hr period. When you plug in to charge the car, it will charge during the lowest rate time. If it won't finish the charge in that time, a pop-up message would ask if you want to stop when the rates change, or keep charging to the limit you set on the battery.
-For the app, when you turn on the heat or a/c , it will ask if you want to use the battery or shore power. (you could set a default to "always use xxx" so you are not prompted each time, if you prefer.

mknox · Mar 6, 2015

mibaro2 said:
I'm thinking that eventually there will be a "Timer" tab on the console. In that tab, you can put your electricity rates for a 24hr period. When you plug in to charge the car, it will charge during the lowest rate time. If it won't finish the charge in that time, a pop-up message would ask if you want to stop when the rates change, or keep charging to the limit you set on the battery.

All they have to do is look at how GM did this with the Volt. You do exactly as you say: input the TOU periods and then you can select if you want the car to be ready based on time or based on time and rates and it will do its best to charge in the lowest cost period.

mejojo · Mar 11, 2015

mknox said:
All they have to do is look at how GM did this with the Volt. You do exactly as you say: input the TOU periods and then you can select if you want the car to be ready based on time or based on time and rates and it will do its best to charge in the lowest cost period.

Perhaps they fixed this with later versions, but with my 2012 Volt, the TOU settings worked great EXCEPT that it didn't realize when you weren't at home. So, first time I tried this I got to work, double-plugged to start immediate charging and then it stopped charging at 10 AM when my Peak rate kicked in at my HOME. I ended up having to revert to telling it I wanted to use the car at 5 AM so that it would charge fully starting some time after 12AM.

Kind of dumb IMO.

Feature request to not charge from "shore power" with TOU rates

Active Member

Member

Active Member

electricmotorglider.com

Well-Known Member

Member

Member

Sig Model S + Sig Model X + Model 3 Resv

Member

Well-Known Member

Roadster#433, Model S#S37

Active Member

Sig Model S + Sig Model X + Model 3 Resv

Well-Known Member

Member

Well-Known Member

Active Member

Member

Well-Known Member

Active Member

Similar threads