Timing my charge with Solar and Net Metering

[mswlogo]

With Net Metering my Solar pushes to the Grid at $.20 kWh (credit) and pulls from grid at $0.25 kWh
You can think of it as a 80% efficient PowerWall (with no vampire drain).

But if I can push that excess solar direct the car, it never reaches the grid and Solar goes to the car at 100%.

So I timed my charge and charge level to today's solar. I saved a whole $1.25

Come summer I could save maybe $3.00 a charge. I can often wait until the weekend to charge.

Be cool if I could automate it.

I tried to schedule the charge to come on when Solar started to ramp up. Stupid Schedule never started. I didn't wait that long though.

You can see I adjusted the max watts on the car from 24A to 16A.

 

[swaltner]

While I haven't messed with it since I currently have full NetMetering, the OpenEVSE unit I have at home includes an optional setting to automatically track real-time solar production. This modulates the pilot signal on the EVSE so the car doesn't draw power off the grid. It needs an external system to monitor the current that it can subscribe to via MQTT.

Quoting from their help info on the EVSE:

Charge Mode:
1. Normal (default):

• Charge at maximum current set by EVSE.

2. Eco (solar PV divert):

• If only solar PV feed available: charge rate is modulated based on solar PV generation.
• If grid +I/-E (positive Import / negative Export) feed is available: charge rate will be modulated by available excess power.
• If EVSE is sleeping: charging will begin when solar PV / excess power > min charge rate.
• Charging will not pause; this avoids excess wear on the EVSE relay and the EV

New Wall Connector load sharing protocol is a project discussed here on TMC where they've decoded the load sharing protocol of the 2nd gen version of the Tesla Wall Connector. This protocol was designed to let multiple wall connectors share a single circuit breaker, reducing your total expenses for charging infrastructure when having multiple EVs in a single household/location. I think this project allows you to replace the master unit with a $30 Raspberry Pi. At that point, you can then write your own cron jobs or other automated scripting to adjust the power availability as desired, possibly implementing a rule set like what the OpenEVSE includes.

 

[mswlogo]

While I haven't messed with it since I currently have full NetMetering, the OpenEVSE unit I have at home includes an optional setting to automatically track real-time solar production. This modulates the pilot signal on the EVSE so the car doesn't draw power off the grid. It needs an external system to monitor the current that it can subscribe to via MQTT.

Quoting from their help info on the EVSE:



New Wall Connector load sharing protocol is a project discussed here on TMC where they've decoded the load sharing protocol of the 2nd gen version of the Tesla Wall Connector. This protocol was designed to let multiple wall connectors share a single circuit breaker, reducing your total expenses for charging infrastructure when having multiple EVs in a single household/location. I think this project allows you to replace the master unit with a $30 Raspberry Pi. At that point, you can then write your own cron jobs or other automated scripting to adjust the power availability as desired, possibly implementing a rule set like what the OpenEVSE includes.

Awesome.

You’re miles ahead of where my head is at. Very clever to tap the load sharing protocol on the wall connector.

Should start a kickstarter project. But you’ve probably talked about that too.

 

[Bob M]

Great discussion. The last 2 years my annual settle with PGE has been $.34 , $.33. With TOU (time of use ) i come out best by using as little electricity as possible during peak time and charging the car during off peak time. The only exception to the straightforwardness of this is if one is feeding in excess of dollar breakeven point. PGE pays only about $.02 / kWh for the excess. When I am pushing into the grid, they offset at the same rate as they would charge me. This system of net metering allows me to use 20% more than I generate yet still break even. When net metering goes away I don’t know what I can do to not get ripped off. Maybe get more of and more efficient panels and invest in storage.

 

[mswlogo]

While I haven't messed with it since I currently have full NetMetering, the OpenEVSE unit I have at home includes an optional setting to automatically track real-time solar production. This modulates the pilot signal on the EVSE so the car doesn't draw power off the grid. It needs an external system to monitor the current that it can subscribe to via MQTT.

Quoting from their help info on the EVSE:



New Wall Connector load sharing protocol is a project discussed here on TMC where they've decoded the load sharing protocol of the 2nd gen version of the Tesla Wall Connector. This protocol was designed to let multiple wall connectors share a single circuit breaker, reducing your total expenses for charging infrastructure when having multiple EVs in a single household/location. I think this project allows you to replace the master unit with a $30 Raspberry Pi. At that point, you can then write your own cron jobs or other automated scripting to adjust the power availability as desired, possibly implementing a rule set like what the OpenEVSE includes.

I got side tracked on the Wall Connector "Decode and raspberry PI" but after reading it can't go below 6 Amps, it feels like a dead end. Other and "Following" the PV surplus. I'm more interest in scheduling charge during "Potential Surplus". So it can be a set it and forget it deal. I just plug in the car and it will charge when PV is "likely" surplus. I have two Wall Connectors (2 different sites, one doesn't have PV).

I went back and reread your post and my eyes had glazed over your comments about OpenEVSE. I dug around a little. It sounds fairly powerful. But can the OpenEVSE, initiate a scheduled "Charge" (and throttle it, now)? And potentially allow a PV surplus input? Technically it looks like it can, but if you take power away and apply it, I thought the Tesla would "fault" and abort charging until it's plugged in again. Is it only UMC or WallConnector that will fault (when it loses power), but other non Tesla charge mechanisms can handle that?

Can you just give a quick summery of what OpenEVSE can do? And the cost to automate something like my opening post is doing. It also seems there is a variable level of DIY options (you can buy premade or build to same specs yourself).

 

[miimura]

Great discussion. The last 2 years my annual settle with PGE has been $.34 , $.33. With TOU (time of use ) i come out best by using as little electricity as possible during peak time and charging the car during off peak time. The only exception to the straightforwardness of this is if one is feeding in excess of dollar breakeven point. PGE pays only about $.02 / kWh for the excess. When I am pushing into the grid, they offset at the same rate as they would charge me. This system of net metering allows me to use 20% more than I generate yet still break even. When net metering goes away I don’t know what I can do to not get ripped off. Maybe get more of and more efficient panels and invest in storage.

Now with so many cities and counties setting up Community Choice Aggregation, you can get paid for the full generation value of your surplus. PG&E will still write off your distribution and transmission surplus though. For example, Silicon Valley Clean energy generation rates on the EV rate plan are $0.020/kWh to $0.053/kWh Winter and $0.022/kWh to $0.198/kWh Summer. On average, this will be higher than the PG&E Net Surplus Compensation without a CCA and you will get some back when you have a dollar surplus generation but are still a net kWh consumer.

 

[coleAK]

So I’m much more low tech. I know that I get the best sun exposure from noon to 6pm in the summer so I plug in as soon as I get home. Current there is 2’ of snow on 18 of my 24 panels.

Also does your meter “sell to grid” whenever your making more than using. For mine it is just a monthly net. So as long as I make less than I use for the month I don’t sell then buy back.

 

[WallyP]

I am a tech noob as well.

All I know is that my solar production during the day can only push to the grid. My utility is SDG&E where my best EVTOU5 rate is super off peak from midnight to 5AM with a current rate of $0.08/kWh so this is when I charge.

Are there any other SDG&E customers who can comment if my strategy is sound?

 

[NathanielHrnblwr]

I am a tech noob as well.

All I know is that my solar production during the day can only push to the grid. My utility is SDG&E where my best EVTOU5 rate is super off peak from midnight to 5AM with a current rate of $0.08/kWh so this is when I charge.

Are there any other SDG&E customers who can comment if my strategy is sound?

You will use self generated power during the day. Any excess will go to the grid. You should charge at night when the rates are lowest.

 

[Glamisduner]

I am a tech noob as well.

All I know is that my solar production during the day can only push to the grid. My utility is SDG&E where my best EVTOU5 rate is super off peak from midnight to 5AM with a current rate of $0.08/kWh so this is when I charge.

Are there any other SDG&E customers who can comment if my strategy is sound?

Thats what I do as well and I was on an old tiered plan. If I pushed 1kWh to the grid I got back 1kWh. It was great except that I ended up in tier 3+ all the time once I got an electric car.

The best plan now is to use as much power as you can when it's cheap 12-6am and 12-2pm on the weekends. If your not using power on the weekends when your producing your basically giving it to SDGE for free, so they can charge you 6-7x as much from 4-9.

 

[ai4px]

I used a SmartEVSE at home and it has a current sense box and a CT transformer... seems to only measure in absolute value though (current is always positive). Seems easy enough to contact the developer and ask him for a programming change. If you could measure the current being sold out your solar inverters and use the EVSE to throttle how much the car takes that would be ideal for your situation.

 

[Bob M]

PG&E makes it very difficult to know what plan you have and exactly what would be the best way to work with it. If I remember I finally went through several people on the phone with them and then my solar installer finally helped me understand. He came back and installed a consumption sensor to work with my emphase system. I can keep P g e honest and plan my usage better. I haven’t tried yet to set the charging schedule on the M3. I still keep getting 2 kinds of advice from Tesla. The manual says charge to only what you expect to use, and Elon’s tweets say keep at 80%??? Anyone feel very confident?

 

[miimura]

PG&E makes it very difficult to know what plan you have and exactly what would be the best way to work with it. If I remember I finally went through several people on the phone with them and then my solar installer finally helped me understand. He came back and installed a consumption sensor to work with my emphase system. I can keep P g e honest and plan my usage better. I haven’t tried yet to set the charging schedule on the M3. I still keep getting 2 kinds of advice from Tesla. The manual says charge to only what you expect to use, and Elon’s tweets say keep at 80%??? Anyone feel very confident?

Your rate plan is clearly stated on your bill. Knowing which one is best for your usage pattern is harder, especially if it will be changing so significantly like when you add an electric vehicle. You should be able to see your net usage data on the PG&E web site unless you have gone out of your way to opt-out of the SmartMeter program.
For most people charging an EV at home, you should be on the EV rate plan and use the car's scheduling to charge Off-Peak between 11pm and 7am. Set the daily charging level to 80%. The only open question is whether you want to plug in every day, or only on days when the battery level is below 50% or 60%. It takes my wife 2-3 days to drive the Model 3 far enough to drop from 80% to 50%. I don't think it makes much difference either way. It may be easier to remember to plug in if you just do it every day.

 

[Bob M]

Thank you. I finally did sort it all out but it wasn’t easy and I am tech and numbers oriented. I believe to go on an EV plan with PG&E I have to have a separate meter installed. With my last two annual settle up virtually at zero I am quite happy with my E6 TOU. With gas prices going up long term and eventual doing away with net metering I can see the need for greater output to handle heat pump s for home heating and water.

 

[miimura]

Thank you. I finally did sort it all out but it wasn’t easy and I am tech and numbers oriented. I believe to go on an EV plan with PG&E I have to have a separate meter installed. With my last two annual settle up virtually at zero I am quite happy with my E6 TOU. With gas prices going up long term and eventual doing away with net metering I can see the need for greater output to handle heat pump s for home heating and water.

You do not have to have a separate meter. The EV rate has two sub-rates. EV-A is for whole house metering and EV-B is for dedicated metering. If you were near zero without EV charging, you will definitely owe something if you add EV charging on the E-6 TOU rate. However, since you are in Antioch, you probably have a lot more A/C use at your home in the Summer than I do in Los Altos. That could be a good reason to avoid the EV rate due to the high price of energy from 2pm-9pm. Since E-6 is closed and you are grandfathered, you should see how it goes and use some of the rate comparison tools that are available after you have a couple months of usage data with your car charging. The PG&E site has a comparison tool and there are third party tools like the PG&E Toolkit iPhone app.

 

[Bob M]

Wow! Finally someone who seems to know this area. I searched all over about 3 years ago when I set up my solar and grabbed E6 the last month it was available. I couldn’t find any tools for effective comparison. Even my installer couldn’t come up with a quick simple answer as to why E6 was best for me at the time. I am not expecting the M3 to change anything as we have had a Volt and my wife and I were able to drive it on electricity most of the time. My M3 trip meter has been averaging 255wh/ mile. If I can rely on this as an accurate measure of electric efficiency, it is close to 4 miles/ kWh while my Volt got about 3.6 as my son the engineer figures it on his Volt. Hopefullly that will make up for the 100% electric driving. I am just waiting for Net metering to change and I believe the review date for that is not too far off. Since the “consumer” will have to foot most of the PGE bankruptcy, I expect the solar subsidy inherent net metering to suffer. My only question is that if I charge say 50kwh at one time (off peak of course) will I get hurt with any tier issues?

 

[miimura]

Wow! Finally someone who seems to know this area. I searched all over about 3 years ago when I set up my solar and grabbed E6 the last month it was available. I couldn’t find any tools for effective comparison. Even my installer couldn’t come up with a quick simple answer as to why E6 was best for me at the time. I am not expecting the M3 to change anything as we have had a Volt and my wife and I were able to drive it on electricity most of the time. My M3 trip meter has been averaging 255wh/ mile. If I can rely on this as an accurate measure of electric efficiency, it is close to 4 miles/ kWh while my Volt got about 3.6 as my son the engineer figures it on his Volt. Hopefullly that will make up for the 100% electric driving. I am just waiting for Net metering to change and I believe the review date for that is not too far off. Since the “consumer” will have to foot most of the PGE bankruptcy, I expect the solar subsidy inherent net metering to suffer. My only question is that if I charge say 50kwh at one time (off peak of course) will I get hurt with any tier issues?

Yes, going over baseline is another risk with E-6. Check your bill to see which Baseline Territory you are in. It's either X or S. It makes a big difference in the Summer because Territory X (temperate strip that is not coastal and not too far inland) has only 9.9kWh per day baseline while Territory S has an allowance of 14.3kWh/day for baseline. Winter is not so different at 10.7 vs. 11.1 kWh/day. If you go over baseline during any given billing period, any incremental EV charging during Off-Peak will cost 27 cents/kWh instead of 18 cents/kWh. The Off-Peak rates are a few tenths of a cent different Summer vs. Winter. I rounded toward the middle. This is more likely to happen in the Winter when your solar generation is smaller.

Baseline Territory Map
PG&E E-6 Tariff

 

[Bob M]

Thanks for looking at this for me. I went to last months bill and looked at all the detail and as far as I can see the tier one allowances are for the whole period and not day by day (I think) . So moving usage around within a period as long as I always charge during off peak times should not affect the bill. If the increased efficiency of the Tesla over the Volt doesn’t produce a net decrease in electricity use it’s because going from 80% or so electric driving to 100% used more electricity than the efficiency increase saved. That entire increase in electric miles matches with gasoline not purchased so the $ net out of pocket savings is way more even though my electric bill may go up by say $8 to $12 a month, I should be Saving two to three times that much in gasoline not used. Please correct me if needed.

 

[miimura]

Correct. Baselines and usage are tallied over the full month billing cycle. You should still see if the PG&E rate comparison tool will work on your account. It doesn't work on mine because I have Powerwalls and PG&E pushed me out of the standard billing system.

 

[Bob M]

Assuming you have the same number of panels, what did the powerwalls do for you especially considering the change in net metering? I considered PG&E my free battery. Though I consume 20% more energy than I produce, I am at zero. Why would I buy these expensive batteries now? I am hoping that by the time net metering goes away panels will be much more efficient and cheaper per watt as well as storage. I would to be energy independent but I think I would need significant storage to do that.