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Discussion Starter #1
I am going to put my federal credit towards a solar panel system next year. I am on an EV rate that has the following price and schedule

Time of Use - Summer/Winter
Peak - $0.45/$0.32
Part peak - $0.25/$0.20
Off-peak - $0.12/$0.12

The October month should be a little below average of energy use used during peak/off-peak. For October my usage was as follows

Peak - 200 kWh
Part peak - 150 kWh
Off peak - 1000 kWh

I was thinking since I have a large house that I would need a 10kW solar array. However, I think the way to go is to get a 5 kW array and just offset my peak/part peak usage. My average use would be about 400 kWh per month for the peak/part-peak. I also did calculations on a Tesla Powerwall and it would be silly to buy one to charge through that instead of the $0.12 per kWh.

A few questions for people who have PG&E... Can you still net meter on the EV-A plan? If so, during the summer if I get credit for a peak kWh at $0.45 would that allow me to use it for about 3.3 kW at off-peak time? It seems that my usage would benefit perfectly for a smaller solar array, even though I have a 3100 sq ft house.
 

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Discussion Starter #3
I'm on PG&E EV-A with Netmetering it works well

recommend you get the biggest system you can - there is more electricity use in your future not less…
I would expect energy to actually decrease for me. I have to get a new air conditioning unit in the next few years and the new ones are more efficient. As technology advances it also gets more efficient. Computers, TV's, lighting, etc... have all been getting more efficient as time goes on. I actually expect less energy use in the future.
 

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I would expect energy to actually decrease for me. I have to get a new air conditioning unit in the next few years and the new ones are more efficient. As technology advances it also gets more efficient. Computers, TV's, lighting, etc... have all been getting more efficient as time goes on. I actually expect less energy use in the future.
but more driving and more EV's in your future will more than offset that decline (if that's the trajectory) you're on - my little family of 5 is now supporting 3 EV's and my usage has gone through the roof! but with off peak rates it's more than offset by the decline in gasoline that I'm no longer buying.

and as electricity prices go up over time the value of what you produce via solar increases...
 

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this link is public and my system's production in San Jose area of California

https://enlighten.enphaseenergy.com/public/systems/VE7v1219451

it's 22 320 watt LG panels - summer it produces 49 kWh/day - lately I've been doing less than 30 kWh days - should bottom out at 20's in December then start going back up to nearly 50 in June/July

http://www.lg.com/us/business/solar-panel/all-products/lg-LG320N1C-G4

with enphase microinverters

22 panels x 320 watts = 7,040 watts - the system should do 12 mega watts/year and it's on pace to do that.

production since April of 2017 has been 7.60 mega watts with average daily being 37.53 kWh/day - we're trending down now given we're on the bombing run for the winter solstice - shortest day of the year and sun is at it worst angle relative to the panels.
 

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Thanks for the link. I am a physicist so real data is really useful for me. I know I am going to annoy the solar people when they come over and also just stop talking to a few when they have no idea what they are talking about. My numbers should be a tad higher in the Central Valley, but it gives me a rough estimate of how much power I should be able to produce with a 7 kWh array. That size array may be exactly what I need according to my calculations if I add a second EV. I would love to add a second EV, but we take frequent trips to visit in-laws 350 miles away and the only EV I would trust would be a Tesla and the supercharging network. I never spent more than $30,000 on a car and spending $55 K on a used Model S seems insane for me.
 

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I never spent more than $30,000 on a car and spending $55 K on a used Model S seems insane for me.
have you test driven one? you won't be disappointed…once you have Autopilot there is no going back - and the seats are much more comfortable.

but the DCFast charging network isn't bad - I found it to be acceptable for my trip to San Luis Obispo - just plan a more leisurely pace…

LG has some 350 watt panels coming online right about now - for about the same $$$ as what I paid for the 320/watt panels - so 22 panels * 350 would be 7,700 watts which is a pretty beefy system

if you have any questions about Solar and/or NEM (PG&E's solar billing) feel free to give me a private message and I'd be happy to chat.

the magic formula for estimating annual usage is from the PG&E NEM form is as follows

system_size_kW. X 1,664^c = annual kWh estimate

so 22 panels @ 320 watts = 7040 or 7.04 kW

7.04 kw * 1,644^c = 11,573.76 kWh/year estimated production. (or 11.573 mega-watt-hours) - if you review your past usage via your PG&E bills you'll be able to calculate pretty well if your planned system will cover your historical usage.

which based on my experience is pretty accurate - and you're right the Central Valley will have slightly increased production - so you should be good.
 

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With PG&E you don't want the EV plans, just go with the TOU they offer. Unfortunately the best plan is the E-6 which is closed (I'm grandfathered in until 2022 or something), it has the best rates. Anyhow the latest TOU plans they have are good too.

I have a 10kW system which I recommend, but really the most important thing is to simply keep you out of the tiering. PG&E baseline is 20kWh/day, whereas the national average use is 30kWh/day. They're trying to encourage us to conserve. The problem with this is that having expensive kWh encourages lots of NG use, and guess where we make our electricity in California? Natural Gas (well except for the renewables). At any rate who cares if you pay a bill at the end of the year, as long as you stay at baseline you are getting the best rate. The trick is that when you start getting into tiers the rates go way up.

We use a lot of electricity (water distiller, EV, computer laboratory, ...) and earn a small check at the end of the year from the power company with a 10kW system, but I tell people to just not get into the tiers!
 

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Discussion Starter #10
With PG&E you don't want the EV plans, just go with the TOU they offer. Unfortunately the best plan is the E-6 which is closed (I'm grandfathered in until 2022 or something), it has the best rates. Anyhow the latest TOU plans they have are good too.

I have a 10kW system which I recommend, but really the most important thing is to simply keep you out of the tiering. PG&E baseline is 20kWh/day, whereas the national average use is 30kWh/day. They're trying to encourage us to conserve. The problem with this is that having expensive kWh encourages lots of NG use, and guess where we make our electricity in California? Natural Gas (well except for the renewables). At any rate who cares if you pay a bill at the end of the year, as long as you stay at baseline you are getting the best rate. The trick is that when you start getting into tiers the rates go way up.

We use a lot of electricity (water distiller, EV, computer laboratory, ...) and earn a small check at the end of the year from the power company with a 10kW system, but I tell people to just not get into the tiers!
I read about this and for my situation I think the EV-A plan is better than the TOU. I used 75% of my energy during the off-peak $0.12 per kWh. The off-peak rate for the TOU is $0.23 per kWh. I charge my car about 700 kWh by itself. If I had an electric car and was using it just around town, I agree the TOU plan would be better.
 

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I read about this and for my situation I think the EV-A plan is better than the TOU. I used 75% of my energy during the off-peak $0.12 per kWh. The off-peak rate for the TOU is $0.23 per kWh. I charge my car about 700 kWh by itself. If I had an electric car and was using it just around town, I agree the TOU plan would be better.
Not sure what you are saying exactly - to be clear I'm saying TOU is best if you have solar. You generate the most during the peak times during the summer, and due to the NEM (2.0 in your case, 1.0 in mine) you bank those credits. If you don't have solar but have a BEV then EV-A is probably better.

BTW I'm an ex-physicist, I quit the field after the SSC was canceled (didn't want to way 15 years until LHC would get around to the Higs :nerd: )
 

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Not sure what you are saying exactly - to be clear I'm saying TOU is best if you have solar. You generate the most during the peak times during the summer, and due to the NEM (2.0 in your case, 1.0 in mine) you bank those credits. If you don't have solar but have a BEV then EV-A is probably better.

BTW I'm an ex-physicist, I quit the field after the SSC was canceled (didn't want to way 15 years until LHC would get around to the Higs :nerd: )
I thought you could still bank the credits for the EV-A plan? Is this not correct? I am pretty sure you can. The big thing for me is I am using 70% of my energy off-peak with the EV-A plan, which is 12 cents per kWh versus the 23 cents per kWh. I could buy a huge solar array and not worry about any cost, but for a 5 to 7 kWh solar array it looks like the EV-A plan is a better deal for me. How would the TOU-A or TOU-B be a better deal? I don't see how the math would work. I saw some worksheets on the Tesla forums and the EV-A plan always is the best deal for me and my usage. I used hypothetical numbers for the solar production in those worksheets.

High energy particle physics, gravitational waves, and exoplanet detection are all amazing fields right now. I can't wait for the James Webb telescope next year. It will change the field of cosmology and galaxy formation models.
 

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Pg&e own site says EV-A is better for my usage in it retro-grade analysis of past usage - EV-A has no tiers and .12xx cents kWh rate...

EV-a is about $500 less a year for me vs any other billing.
 

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I thought you could still bank the credits for the EV-A plan?
Yes I believe you bank with all of them, but the tiered rates with the high summertime peak rates are the ones you want, because electricity is fungible. In other words you want to maximize your earning, rather than worrying about your off peak pricing. The reason is because you'll earn more in solar credits than you'll use in off peak, because the panels run every day and generate lots of kWh, depending on size. Anyhow its complicated and depends on your circumstances but these are the general guidelines my solar installer recommended and FWIW my calculations agreed.

High energy particle physics
I think that was pretty boring unfortunately, I mean we went looking for His, and we found it. Would have been more interesting if we hadn't.

gravitational waves
Yeah I freaked when LIGO actually hit pay dirt, didn't think it would happen this soon, if ever. I underestimated how good we can get interferometry.
 

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So, we’re on E-6 on PG&E right now. We have solar on the roof. Prior to getting the Bolt, at the end of the true-up period for the last 3 years, we had a monetary credit of ~$50, plus the $120 in mandatory bill minimums that we couldn’t use. No excess kWh production, just excess monetary credits. So we were walking away from $170 worth of electricity each year. Kinda sucks, but it was worth it to cut our electricity bill which was ~$250 a month on average. Now we just pay ~$10 to PG&E, and ~$110 to the leasing company. Instant $120 a month savings.

Since getting the Bolt, our usage has obviously gone up, especially now since I’m working again and driving between 80 and 100 miles a day. Looking at my daily usage, looks like I’m using about 20 to 30 kWh of power for charging every night, or about an extra 400 to 500 kWh for the month. This has pushed us into Tier 2, which is 24 cents a kWh for off-peak. Ouch.

I’m contemplating going on EV-A. Reasons I haven’t yet is because the peak and partial peak times are different than that of E6, which has an effect on how much we’re earning from excess Solar production during the day, especially in the afternoon. And winter rates are higher on EV-A than that of E6. Earlier this year I downloaded all my usage data, loaded it into a spreadsheet, and inputted the EV-A rates as a comparison and the result was that EV-A was a whopping $20 or so cheaper. However, this didn’t take into account the new usage I’ve got with the Bolt. The extra usage from the Bolt is definitely pushing me into Tier 2, which I wasn’t in last year for the same time periods. So switching would help since it would be ~12 cents a kWh instead of the 16 to 24 cents I’m paying now.

The other complicating factor is that the county of San Mateo decided to make Peninsula Clean Energy the new energy provider for all residents via the CCA program. They have a slightly different rate structure (which is supposed to be 5% cheaper than PG&E on the generation side), and my bill from PG&E now includes charges from them for the electricity they supply, but I get a credit for the energy PG&E didn’t directly supply. In theory it’s supposed to be roughly the same cost, but our energy is supposed to be primarily from clean sources (50% instead of the 30% that PG&E currently supplies). There’s an option for 100% clean sources, but you pay about a 10% premium for that option.

Decisions, decisions...,
 

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EV-A has no tiers! you can use as much electricity as you want and it's all the same price - off peak charging with no tiers and an EV is a fairly good combination - you also get peak rate credits for excess solar during the day - and off peak on weekends!

EV-A has worked well for me - and I like the unlimited off-peak power at a fixed rate.
 

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Question from Texas

I'm on PG&E EV-A with Netmetering it works well

recommend you get the biggest system you can - there is more electricity use in your future not less…
David;
Could adding a battery system make economical sense in your area? In Texas, I have an option of solar days/free nights that would result in essentially nothing more than a "subscription" cost of electricity of about $120/year IF (a big if) I could shift all my grid energy to "night" - 9:00 pm to 6:00 am. With significant solar, a large enough battery and a really good energy control app (AC thermostatic control in summer), it seems possible to move at least the majority of energy to night usage - mainly dependent on my wifes' tolerance of temperature swings:laugh:.
I also have the option of "real time" energy rates, however, since distribution is the majority of total rate, I don't believe that option would result in a significant reduction in annual energy costs.

Being a solar/EV enthusiast, this is more musing about what areas of our Country have strong economic incentives to go both solar and EV and under what capital cost constraints - with an "eye" toward true "smart grid" apps for EVs. Grid inverters with DC bus integrated home backup batteries (e.g. Pika/solaredge) now have the technologies that actually incorporate the ~400 VDC lithium tech batteries for both backup and load shifting (which begs the question of V2G for EVs to help provide significant battery energy).

I have met with Tesla on home solar and their offering (at least in my area) makes no sense, which makes sense with our "cheap" energy?.

Appreciate any inputs.
 

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I've done the math 700,527,893 times as I desperately want to get a Tesla power wall.

to be CLEAR there is only a minimal payback period that makes any rational sense for a Tesla Powerwall given net metering - and I'd done the math over and over and over - it's just make no sense to me...

it's complicated but the simplest basic approach is as follows:

1. any savings to be realized is based on running your house off battery during "peak" billing times (using cheap nighttime power to benefit the house when you'd be paying "peak" rates
2. the most savings you can realize is based on the spread between your peak rate & your off peak rate
3. the total amount of money you can make on the spread is limited by your battery capacity
4. and you only realize this daily money if you use _ALL_ of your battery capacity each/every day - which is unlikely - so you actually save less money if you don't "empty" the batteries each day
5. there is a 10% loss to "fill" the battery, and there is another 10% loss to "use" the battery - this makes the math worse
6. the math is even more complicated since PG&E has a "mid-peak" rate for most of the day which has an even smaller $$$ "spread" for potential "savings"

example:

1 power wall (14 kWh) capacity
PG&E peak/off-peak spread $0.45/kwh (peak) - $0.12/kWh (off-peak) = $0.33/kWh
maximum daily savings = (14 (kWh) * .8 (AC/DC/AC loss)) * .33 (kWh spread) = 11.2 kWh * .33 = $3.70/day
cost of power wall installed ~$8000.00 = 2162 days to "break" even _IF_ you use the entire power wall EVERY day - note PEAK and OFFPEAK rates are different on weekends, which makes the math even worse...
2162 / 365 = 5.92 years to break even

with netmetering in place in California w/PG&E you get TOU retail credits for excess solar during the day (mid-peak/peak), and you consume at TOU retail price during off-peak - with _NO_ 20% loss for in/out (AC/DC/AC)

so I generate power and get a full $0.45/kwh credit with PG&E (minus what ever the house is currently using during production), and then later that night I consume power and pay $0.1254/kwh for what I use…basically PG&E _IS_ the battery - and there is no penalty for kWh in/out due to AC/DC/AC conversion

basically in my opinion it's better for me to pump my excess solar usage into PG&E's grid and get full retail TOU $$$ credit mid-peak/peak rates during the day (with no 20% loss for AC/DC/AC conversion) - and then consume back from PG&E's grid at night when rates are cheaper…

where the power wall does make sense is (and I've placed an order since I lose power for 1-6 hours about every two months) is whole house backup to bridge "modest" short term outages - I plan to get two power walls @ 28 kWh - and that's enough to run the house with no change in life style for about 1.5 days (no AC use and no EV charing while on battery)

the tesla power wall is good for two applications in my opinion

1. off grid applications - probably the best system on the market right now- but pricey
2. whole house backup for the occasional grid outage (but not to charge your EV)

those are my thoughts/opinion.

PG&E has moved to billing a "grid connect" fee of about $10/month and I've decide that I'm ok with that in order to use them as "unlimited" battery with "overdraw" privileges…

basically there is no way I can provision a battery system big enough to handle my daily overproduction and use it later (during the summer my 14 kW Solar system produces > 80 kWh/day) and when i'm gone on vacation for one or two weeks that is 490-980 kWh over production for a 1-2 week vacation - that "overproduction" is "stored by PG&E and I can use it winter when my system is barely producing 28 kWh/day…

a powerwall system that could store 980 kWh = would be ~70 power walls @ $5000/each = $350,000 to store a months worth of over production ;-)

I'm really really really happy to use PG&E as my "battery" for $120/year - and they let me take more than I produce for $0.1252/kWh - it's like a checking account I can overdraw for minimal pennies on the $
 

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Thanks for the quick reply - the results of your analysis certainly do not surprise me. With your "retail credits" it seems better to put any battery costs into more grid-tied solar.

Does PG&E offer a contract similar to solar days/free nights? This type contract would offer a significant pay back with enough battery storage to significantly shift all/most grid energy to "night". OTOH, the energy resellers will likely stop such contracts if a significant number of households were to do so!

I'm hopeful that eventually the EV manufacturers will focus on V2G so that the excess battery capacity can play a significant role in load shifting, especially if "smarts" can be utilized for not only load shifting, but also for better charging profiles for EVs. LG, Panasonic, Tesla and others that offer seamless battery integration at the high voltage DC bus level is a great start.
 

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It's is really complicated and situationally dependent, and difficult to accurately analyze. Myself and several other engineers worked at it for weeks and at best came up with rules of thumb, but David captured it above. Here's my take on battery (e.g. Powerwall) vis-a-vis solar panels. I think a battery only makes sense to offset the inability to put more panels up. The reasons are follows

  • The cost/kWh is quite a bit higher for storage versus panels
  • Batteries obviously don't generate, so all you can do is arbritrage, whereas panels actually make money (and I believe PG&E has restrictions on your ability to arbitrage with storage)
  • Solar panels are a screaming deal as David outlined above, you sell at the absolute highest peak of the year which is the time of your highest production, and then you get to use those credits during a years time frame
  • So it has built in tremendous arbitrage - since you don't control the sun you just generate whatever you generate and PG&E lets you eat those credits at the cheapest part of the year
It's crazy how good NEM 1/NEM 2 are in California.

the tesla power wall is good for two applications in my opinion

1. off grid applications - probably the best system on the market right now- but pricey
2. whole house backup for the occasional grid outage (but not to charge your EV)
Exactly. If you're looking for a good power deal just put panels up, a battery is just good for backup.
 
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