Calculating Cost to Charge eGolf with Solar in SoCal

[uncleGarage]

I have a 6.8kW solar array. I'm in year one and just trued-up for $49.00 where I paid $3200.00 for electricity costs in the year prior. Once I get my L2 EVSE installed and start charging my eGolf, I'll be using more electricity. But how much more is the question.

We roughly factored an EV in my solar sizing calculations but that was inexact at best. I've heard one review on yT where the eGolfer said it costs him about 30.00 per month to charge. He didn't provide details though.

My question: can anyone point me to information on how to understand the costs of charging my eGolf, with an on-grid array? I'm in SoCal with SDGE. I assume there are optimal times to charge and suboptimal like 23.00 - 05.00 and 16.00 - 21.00 respectively. What else do I need to factor? I'd like to get as granular as I can with my calculations. According to my research, my L2 EVSE will be plugged into a 240v receptacle and can pull anywhere between 30 and 80 AMPs depending on the model.

Thoughts? Comments?

 

[miimura]

The e-Golf will never pull more than 30 amps, regardless of your charging equipment. That is the limitation of the on-board charger. If you have an SE without the Quick Charge package, then it will be no more than 15 amps.

In order to know your charging costs, we need to know which rate plan you're on. I looked at the available SDG&E rates and the applicable ones for solar customers seem to be DR-SES and EV-TOU-2. The EV-TOU rate must be separately metered from your house, either with a separately wired utility meter, or a sub-meter provided and provisioned under the Sub-Meter Pilot Program. The Phase 2 Pilot Program is starting in January 2017. The main benefit of the Sub-Metering pilot is that you can get the EV rate without affecting your house rates. As long as you are positive on your true-up and you don't want to use solar net metering credits to reduce your EV charging costs, then it makes sense to join the sub-meter pilot.

If you are going to continue on your current rate plan and just want to know the incremental cost of charging, then it is relatively straight forward as long as you use the charge timers to have the car charge during the Off-Peak or Super-Off-Peak rate periods.
DR-SES Off-Peak is $0.209/kWh 10pm-6am Summer and $0.204/kWh 6pm-6am Winter
EV-TOU-2 Super Off-Peak is $0.178/kWh Summer and $0.189/kWh Winter, Midnight to 5am all year.

All you would need to do is take your monthly mileage and your typical driving efficiency to come up with a typical kWh/month figure, then divide by 85% for charging efficiency. For example, if you drive 1,000 miles per month at 4mi/kWh, then you would use 250kWh/month from the battery and 294kWh/month from the utility. If you are on DR-SES, that would be $61.45 for a summer month or $52.33 on EV-TOU-2 for a summer month.

However, if you want to change rate schedules then it gets a whole lot more complicated. The reason is that you need to know your usage by time period and the time periods are different for different rate schedules. So, your charges could go up during the Peak time period but be lower for your EV charging Super Off-Peak. One thing to notice is that the EV-TOU-2 Peak period goes until 8pm while the DR-SES only goes to 6pm. That extra two hours will burn up some of your surplus Peak solar generation.

I am in PG&E Territory and I made an Excel spreadsheet that uses downloaded SmartMeter data to calculate energy charges on all the applicable residential rates. I haven't updated it in a while and it's based on PG&E's rate schedules. However, it is possible to plug in the times and rates for another utility. If you're good with spreadsheets, I can post the link and give you some tips on how to modify it.

 

[BarryMW]

SIDE NOTE:
Due to just having your true-up I'll assume you are NEM1.0 and have not altered (or plan to alter) your array and switch to NEM2.0
I've just gone solar only to find I missed NEM1.0 by a couple of days "and I aint appy!"

SOLAR:
With your array production and consumption being so well balanced, your car charging will be predominately from purchased electricity.

AMOUNT YOU PURCHASE:
EV's get better MPG in slow traffic than at freeway speeds.
I'm in the bay area and hover around 4.6 Miles Per KWh with mixed driving.
My number will vary approx. 0.5M/KWh downwards if I freeway only, or 0.5M/KWh upwards around town only.
I am a gentle driver..... YMMV

COST:
Given the info above, you should be able to estimate the type and range of your daily use.
Assuming you have an understanding of your selected electricity Rate Plan, you should be able to calculate cost per month.

OR skip it all together and go with this calculation
A gallon of gas is $2.40
My existing cars MPG 26MPG

One KWh purchased at night (off-peak) is $0.21 (Assumes your are on a TOU time of use rate plan)

Assuming 4.6M/KWH

$0.21 divided by 4.6miles multiply by 26MPG = $1.18

You will no longer pay $2.40 per Gallon of gas...... you will pay $1.18 for electricity to travel the same 26 miles.
I was charging for free at work. This brought that number down to approx. $0.70

You will not change the oil in the vehicle.
You will not change the brakes in the vehicle.
I believe the supplied LRR tires will make it through my full 45,000 mile lease. So maybe no tires.
Windshield wipers at my current 22,000 miles are close to needing replacement.

Point is, maintenance for me has been negligible.
I wish I had NOT rolled the service visit costs into the lease. But being my first lease & first EV, I fell for the sales pitch.


Hope this helps

Barry

 

[uncleGarage]

SIDE NOTE:
Due to just having your true-up I'll assume you are NEM1.0 and have not altered (or plan to alter) your array and switch to NEM2.0
I've just gone solar only to find I missed NEM1.0 by a couple of days "and I aint appy!"

SOLAR:
With your array production and consumption being so well balanced, your car charging will be predominately from purchased electricity.

AMOUNT YOU PURCHASE:
EV's get better MPG in slow traffic than at freeway speeds.
I'm in the bay area and hover around 4.6 Miles Per KWh with mixed driving.
My number will vary approx. 0.5M/KWh downwards if I freeway only, or 0.5M/KWh upwards around town only.
I am a gentle driver..... YMMV

COST:
Given the info above, you should be able to estimate the type and range of your daily use.
Assuming you have an understanding of your selected electricity Rate Plan, you should be able to calculate cost per month.

OR skip it all together and go with this calculation
A gallon of gas is $2.40
My existing cars MPG 26MPG

One KWh purchased at night (off-peak) is $0.21 (Assumes your are on a TOU time of use rate plan)

Assuming 4.6M/KWH

$0.21 divided by 4.6miles multiply by 26MPG = $1.18

You will no longer pay $2.40 per Gallon of gas...... you will pay $1.18 for electricity to travel the same 26 miles.
I was charging for free at work. This brought that number down to approx. $0.70

You will not change the oil in the vehicle.
You will not change the brakes in the vehicle.
I believe the supplied LRR tires will make it through my full 45,000 mile lease. So maybe no tires.
Windshield wipers at my current 22,000 miles are close to needing replacement.

Point is, maintenance for me has been negligible.
I wish I had NOT rolled the service visit costs into the lease. But being my first lease & first EV, I fell for the sales pitch.


Hope this helps

Barry

Tremendously helpful. Thank you Barry.

 

[uncleGarage]

The e-Golf will never pull more than 30 amps, regardless of your charging equipment. That is the limitation of the on-board charger. If you have an SE without the Quick Charge package, then it will be no more than 15 amps.

In order to know your charging costs, we need to know which rate plan you're on. I looked at the available SDG&E rates and the applicable ones for solar customers seem to be DR-SES and EV-TOU-2. The EV-TOU rate must be separately metered from your house, either with a separately wired utility meter, or a sub-meter provided and provisioned under the Sub-Meter Pilot Program. The Phase 2 Pilot Program is starting in January 2017. The main benefit of the Sub-Metering pilot is that you can get the EV rate without affecting your house rates. As long as you are positive on your true-up and you don't want to use solar net metering credits to reduce your EV charging costs, then it makes sense to join the sub-meter pilot.

If you are going to continue on your current rate plan and just want to know the incremental cost of charging, then it is relatively straight forward as long as you use the charge timers to have the car charge during the Off-Peak or Super-Off-Peak rate periods.
DR-SES Off-Peak is $0.209/kWh 10pm-6am Summer and $0.204/kWh 6pm-6am Winter
EV-TOU-2 Super Off-Peak is $0.178/kWh Summer and $0.189/kWh Winter, Midnight to 5am all year.

All you would need to do is take your monthly mileage and your typical driving efficiency to come up with a typical kWh/month figure, then divide by 85% for charging efficiency. For example, if you drive 1,000 miles per month at 4mi/kWh, then you would use 250kWh/month from the battery and 294kWh/month from the utility. If you are on DR-SES, that would be $61.45 for a summer month or $52.33 on EV-TOU-2 for a summer month.

However, if you want to change rate schedules then it gets a whole lot more complicated. The reason is that you need to know your usage by time period and the time periods are different for different rate schedules. So, your charges could go up during the Peak time period but be lower for your EV charging Super Off-Peak. One thing to notice is that the EV-TOU-2 Peak period goes until 8pm while the DR-SES only goes to 6pm. That extra two hours will burn up some of your surplus Peak solar generation.

I am in PG&E Territory and I made an Excel spreadsheet that uses downloaded SmartMeter data to calculate energy charges on all the applicable residential rates. I haven't updated it in a while and it's based on PG&E's rate schedules. However, it is possible to plug in the times and rates for another utility. If you're good with spreadsheets, I can post the link and give you some tips on how to modify it.

Thanks for all of the great information and guidance miimura. I'm primarily in Tier 1 & 2 san TOU is probably not best for me.

 

[JoulesThief]

What are you paying per kW for tier 1 and tier 2 after all the taxes are added in? I get LADWP for my utilites, and tier 1 is about 17.7c per kwh for first 1000 kW over a 2 month billing cycle. Tier 2 is closer to 23.3c per kwh. Currently, we do not get any time breaks for charging at off peak hours, though I still try to charge from 4-7 am, as my voltage at that time of a 24 hour period will be at 245 to 246V pretty consistently, telling me hardly anybody is using electricity off the grid at that time in the morning. A 3 pm start of charge will show 239-237V, depending on how hot the day is. and how humid the air is.


I drive very, very gently, almost all surface streets and BLVDs, doing 35 to 45 mph, trying to time all green lights, not using hardly any accessories, if I can do so. I crack the driver and passenger front windows 1" open. I see 6.0 to 6.3 -6.4 miles per kWh from the battery. My calculations from my Juice Box Pro show that I am getting about a 91 % efficiency from kwh I bought charging, to kwh that the battery is showing used when driving and being discharged. YMMV... 240V and 30 amps from a Juicebox 40 pro might be better or worse than the EVSE unit you use.

I find the highest efficiency of battery charge when I complete getting a full charge, and then drive off within the next 15 to 30 minutes upon completion of the recharge. Leaving shortly after completion of a full charge, it is my belief, allows you to use up the excessive surface charge sitting in the battery immediately after it's completed charging, instead of it dissipating off and being lost. Li Ion batteries don't like being stored fully charged for any length of time. Use some of it, as soon as it completes fully recharging. YMMV, these are my efficiency observations.... driving off on a freshly fully recharged hot battery, seems in my observations, to be worth another 2 or 3 miles or .4 to .5 KWH of free miles traveled, if you take off while the battery is still hot from being recharged.

 

[forbin404]

SCE has a TOU-D plan where it's roughly 13c at night and 17 peak, and 32 super peak.

 

[uncleGarage]

What are you paying per kW for tier 1 and tier 2 after all the taxes are added in? I get LADWP for my utilites, and tier 1 is about 17.7c per kwh for first 1000 kW over a 2 month billing cycle. Tier 2 is closer to 23.3c per kwh. Currently, we do not get any time breaks for charging at off peak hours, though I still try to charge from 4-7 am, as my voltage at that time of a 24 hour period will be at 245 to 246V pretty consistently, telling me hardly anybody is using electricity off the grid at that time in the morning. A 3 pm start of charge will show 239-237V, depending on how hot the day is. and how humid the air is.

I drive very, very gently, almost all surface streets and BLVDs, doing 35 to 45 mph, trying to time all green lights, not using hardly any accessories, if I can do so. I crack the driver and passenger front windows 1" open. I see 6.0 to 6.3 -6.4 miles per kWh from the battery. My calculations from my Juice Box Pro show that I am getting about a 91 % efficiency from kwh I bought charging, to kwh that the battery is showing used when driving and being discharged. YMMV... 240V and 30 amps from a Juicebox 40 pro might be better or worse than the EVSE unit you use.

I find the highest efficiency of battery charge when I complete getting a full charge, and then drive off within the next 15 to 30 minutes upon completion of the recharge. Leaving shortly after completion of a full charge, it is my belief, allows you to use up the excessive surface charge sitting in the battery immediately after it's completed charging, instead of it dissipating off and being lost. Li Ion batteries don't like being stored fully charged for any length of time. Use some of it, as soon as it completes fully recharging. YMMV, these are my efficiency observations.... driving off on a freshly fully recharged hot battery, seems in my observations, to be worth another 2 or 3 miles or .4 to .5 KWH of free miles traveled, if you take off while the battery is still hot from being recharged.

Hi JoulesThief.

Thank you for your post and sharing your story.

I am paying .21¢ for Tier 1 and 23¢ for Tier 2 per KWh. I was just reading on the SDGE site that if I am not in Tier 3 then I most likely do not need to participate in a TOU plan. But the figures forbin404 quoted above makes me want to reconsider this recommendation. I'm currently Standard - DR-Residential.

As for my EVSE - I'm installing an ClipperCreek HCS-50P Level 2 charger (40 Amp (9.6kW max).

My family and I manage to have wild swings in our electricity consumption. In the 32-day billing cycle from 03/31/17 - 05/02/17 we over-produced and generated a surplus of -626 KWh with our 6.89 kW array. When the hot weather hits the wifey jacks the A\C and the surplus gets defenestrated.

What I am focused on is trying to determine how charging the eGolf will effect my bill. I plan on charging at night when rates are lowest and then using the ~80 mile range during the day. Our usage is such that we can likely cover all of our driving in a given day without needing to re-charge. We'll just plug in at night when we all retire.

 

[JoulesThief]

How many miles per month will you drive? Look on your infotainment center and look up your long term kwh used and over how many miles traveled. Let us know what your miles per kwh is averaging. As summer gets here, you will get less miles per kwh if you run the AC on the e-Golf. Nothing is free.


Estimate also, for us, the miles traveled per day, daily. And days not in use.

 

[GlennD]

What are you paying per kW for tier 1 and tier 2 after all the taxes are added in? I get LADWP for my utilites, and tier 1 is about 17.7c per kwh for first 1000 kW over a 2 month billing cycle. Tier 2 is closer to 23.3c per kwh. Currently, we do not get any time breaks for charging at off peak hours, though I still try to charge from 4-7 am, as my voltage at that time of a 24 hour period will be at 245 to 246V pretty consistently, telling me hardly anybody is using electricity off the grid at that time in the morning. A 3 pm start of charge will show 239-237V, depending on how hot the day is. and how humid the air is.

I drive very, very gently, almost all surface streets and BLVDs, doing 35 to 45 mph, trying to time all green lights, not using hardly any accessories, if I can do so. I crack the driver and passenger front windows 1" open. I see 6.0 to 6.3 -6.4 miles per kWh from the battery. My calculations from my Juice Box Pro show that I am getting about a 91 % efficiency from kwh I bought charging, to kwh that the battery is showing used when driving and being discharged. YMMV... 240V and 30 amps from a Juicebox 40 pro might be better or worse than the EVSE unit you use.

I find the highest efficiency of battery charge when I complete getting a full charge, and then drive off within the next 15 to 30 minutes upon completion of the recharge. Leaving shortly after completion of a full charge, it is my belief, allows you to use up the excessive surface charge sitting in the battery immediately after it's completed charging, instead of it dissipating off and being lost. Li Ion batteries don't like being stored fully charged for any length of time. Use some of it, as soon as it completes fully recharging. YMMV, these are my efficiency observations.... driving off on a freshly fully recharged hot battery, seems in my observations, to be worth another 2 or 3 miles or .4 to .5 KWH of free miles traveled, if you take off while the battery is still hot from being recharged.

Hi JoulesThief.

Do not over buy your EVSE. Even with a 40A EVSE the car will only charge at 30A. A 30A EVSE on a 40A circuit is fine. Actually the Clipper Creek is rated at 32A so you have a 2A reserve.

Thank you for your post and sharing your story.

I am paying .21¢ for Tier 1 and 23¢ for Tier 2 per KWh. I was just reading on the SDGE site that if I am not in Tier 3 then I most likely do not need to participate in a TOU plan. But the figures forbin404 quoted above makes me want to reconsider this recommendation. I'm currently Standard - DR-Residential.

As for my EVSE - I'm installing an ClipperCreek HCS-50P Level 2 charger (40 Amp (9.6kW max).

My family and I manage to have wild swings in our electricity consumption. In the 32-day billing cycle from 03/31/17 - 05/02/17 we over-produced and generated a surplus of -626 KWh with out 6.89 kW array. When the hot weather hits the wifey jacks the A\C and the surplus gets defenestrated.

What I am focused on is trying to determine how charging the eGolf will effect my bill. I plan on charging at night when rates are lowest and then using the ~80 mile range during the day. Our usage is such that we can likely cover all of our driving in a given day without needing to re-charge. We'll just plug in at night when we all retire.

 

[GlennD]

Oops, my reply was in the quote section. My bad.

 

[uncleGarage]

Oops, my reply was in the quote section. My bad.

Yea. That confused the heck out me for a few. I didn't recall writing that! Very interested in hearing more about your statement

Do not over buy your EVSE. Even with a 40A EVSE the car will only charge at 30A. A 30A EVSE on a 40A circuit is fine. Actually the Clipper Creek is rated at 32A so you have a 2A reserve.


I was going to purchase a ClipperCreek HCS-50P which is 40 AMPs. This is more for enabling flexibility. But you're saying for the eGolf anything above 30 AMPs is a waste?

 

[miimura]

Oops, my reply was in the quote section. My bad.

Yea. That confused the heck out me for a few. I didn't recall writing that! Very interested in hearing more about your statement

Do not over buy your EVSE. Even with a 40A EVSE the car will only charge at 30A. A 30A EVSE on a 40A circuit is fine. Actually the Clipper Creek is rated at 32A so you have a 2A reserve.


I was going to purchase a ClipperCreek HCS-50P which is 40 AMPs. This is more for enabling flexibility. But you're saying for the eGolf anything above 30 AMPs is a waste?

Yes, the e-Golf will never pull more than 30 amps from any EVSE. However, if you get another EV in the future it can take advantage of the higher capacity EVSE. Today, only Tesla on-board chargers in their cars and the ones they provided to Toyota for the RAV4 EV and the Mercedes B-Class can pull 40 amps or more. It's good for future proofing. Your house is certain to outlast your car.

 

[uncleGarage]

Perfect. Thanks miimura. Just the information I was looking for. I agree that going with a higher-amperage EVSE is the best bet. I see that you have run two different EVSE vendors. Can you share your thoughts?

The ClipperCreek is not a smart EVSE and I want to understand the ramifications of this. What kind of relationship can exist between the EVSE and an EV"s onboard charger? I assume that in certain instances they can communicate with each other so that the EV can signal the EVSE that it is fully charged and that the EVSE should stop.

 

[miimura]

I have one EVSE and 50 amp circuit for each EV. I've had my RAV4 EV and Leviton EVB40 EVSE since April 2013. At the time it was the only 40 amp EVSE below $1,000 with a J1772 connector. When we got the e-Golf, we used the provided 120V cord for almost 6 months. If it wasn't done when I woke up in the morning, I would unplug the RAV from the Leviton and plug in the e-Golf. That would always get it to full by the time my wife went to work. However, that was putting some of our charging outside the cheapest electric price window. I saw that somebody was selling their Jesla, a J1772 converted Tesla mobile EVSE, for about 40% off the new price, so I jumped on that. It's good because it is very portable and can automatically adjust the signal to the car to match the capacity of the circuit based on its plug adapters. In a year and a half, I haven't yet taken advantage of the portable nature of this EVSE.

To me, there are only two good reasons to use a Smart EVSE. First is energy metering. If you really want to know how much energy you are using to charge your car, the easiest way to get that data is to use an EVSE with internal metering. If you get a home energy monitor, you can install a channel just for the EV charging circuit too, but that's much more involved. The second is demand management. If you are in California, there are programs starting up where a Smart EVSE can be used to shift EV charging loads to either match renewable power generation or shave down peak grid loads. ChargePoint and eMotorWerks are the two vendors I know of that are involved in this. You can get some compensation for participating in these load management schemes. I wouldn't bother with other EVSEs that just have built-in timers and such.

Clipper Creek is a very highly regarded American vendor of EVSEs and they do have two specialized products relevant to this discussion. First is the JuiceNet enabled HCS-40. It adds the Smart features of the JuiceBox to the ETL Certified Clipper Creek unit. Second is the Share2 edition of the HCS-40. It allows the pair of EVSE to share a single circuit, dividing the available current between two cars dynamically by modulating the Pilot signal sent to each car.

Fundamentally, an EVSE is a safety device. All it is doing is telling the car how much current it is allowed to draw. When the car indicates that it is connected and wants to draw power, the EVSE activates a relay and delivers the wall power to the car. Until that point, there is no high voltage at the vehicle connector, so you can't get shocked. The EVSE doesn't know or care how full the car is. It's the car's job to properly manage its own charging. When the car is done, it drops the signal to the EVSE and the EVSE shuts off the power. Also, when you push the button on the J1772 connector, the car is supposed to immediately stop charging and tell the EVSE to disconnect the power.

 

[GlennD]

A bigger EVSE can future proof your installation but all currently available cars follow the J1772 standard. That means if you have a car like my old B, it will charge just fine at 30A instead of the 40A it was capable of. Going to a 40A EVSE is a whole lot more than a 30A EVSE. Likely because it is heaver built and much lower demand.

 

[JoulesThief]

A bigger EVSE can future proof your installation but all currently available cars follow the J1772 standard. That means if you have a car like my old B, it will charge just fine at 30A instead of the 40A it was capable of. Going to a 40A EVSE is a whole lot more than a 30A EVSE. Likely because it is heaver built and much lower demand.

I believe a 40 amp JuiceBox is competitively priced with all other 30 amp units out there. Matter of fact I bought a sample 40 amp unit directly from e motorwerks off of e-Bay for $300 last year. Inside, the Potentiometer had been adjusted down to 30 amps, max. The relay and points were brand new in it, replaced just before e-motorwerks sent it off to me. I've since adjusted it up to 40 amps, in case I come across a smoking deal on a B model Benz, used.

 

[GlennD]

40A is fine. your eGolf will only draw 30A from it. My late B would take it all. From what I can see the current non UL approved JuiceBox is a fine device. The redesign looks really nice. It is nice to have lower priced alternatives.

I am an OpenEVSE person but in spite of Chris's opinion the JuiceBox is a good device. It is just lacking in the open Linex documentation. At least the OpenEVSE source code is public. Not so much in the later design JuiceBox.

 

[vetaldj]

I charge my eGolf each day from about 20 miles to full at home. I'm on TOU-1 rate with separate meter (Beta Program from SCE and ChargePoint) and my bill is about $25-$30 per month.
I've used 130 kWt last month. Off peak is about $.13 and OnPeak is about $.33 for summer and $.21 for winter.

 

[forbin404]

I charge my eGolf each day from about 20 miles to full at home. I'm on TOU-1 rate with separate meter (Beta Program from SCE and ChargePoint) and my bill is about $25-$30 per month.
I've used 130 kWt last month. Off peak is about $.13 and OnPeak is about $.33 for summer and $.21 for winter.

Interesting, SCE changed my rates AGAIN.

It's 17 / 33 / 17 / 13 it was 28 / 33/ 28/ 13.

I guess it was a typo.

Vetaldj, do you have to have a separate meter? The TOU-B-D is as good as TOU-EV-1