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What is your solar usage offset ?

Az_Rael

Well-Known Member
Supporting Member
Jan 26, 2016
5,675
8,979
Palmdale, CA
I don't know that 70% is standard. Tesla Energy was initially trying to get me over 90%, but after I did some math myself based on my usage, I went with an 80% offset. That will get me to a net zero $$ for the year (which isn't the same number as net zero kWh).

It depends on how netmetering works in your area. Get a few quotes from other installers and see what they recommend.
 
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I don't know that 70% is standard. Tesla Energy was initially trying to get me over 90%, but after I did some math myself based on my usage, I went with an 80% offset. That will get me to a net zero $$ for the year (which isn't the same number as net zero kWh).

It depends on how netmetering works in your area. Get a few quotes from other installers and see what they recommend.

Thanks ! You make a good point re net $$$ vs net kWH. My goal is definitely net zero $$$ but i’ve been equating it to net zero kWh. They were trying to explain to me that 70% usage offset will get me net zero $$$.

I have five other quotes and they have all quoted a similar sized system.
 
For everyone who has home solar installed, how much of your pre-solar usage (in percentage) does your solar installation offset ?

I talked to a Tesla Energy sales consultant today and he told me that 70% usage offset is standard. Just want to see what everyone’s experience here.

Thanks !
Chris
148%

For the past 5 years....I have made more solar energy than I've used....to the tune where they now pay me.
 
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dhrivnak

Active Member
Jan 8, 2011
4,577
4,057
NE Tennessee
For everyone who has home solar installed, how much of your pre-solar usage (in percentage) does your solar installation offset ?

I talked to a Tesla Energy sales consultant today and he told me that 70% usage offset is standard. Just want to see what everyone’s experience here.

Thanks !
Chris
For the last 3 years I am at 99.8%. And I have no idea why you would want or design to be only 70%
 
I designed it with 110% assuming I had a model 3 at the time. But it was hard for me to really gauge since I was in a new house. If you have more afternoon sun on your panels then you would make more money in peak time, but all depends on how it adds up. If I end up having more electricity after 12 months, I will probably look at getting an electric water heater.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,767
2,747
Northern California
Well the optimal is a bit of a trick question and a moving target. I assume you are a PG&E customer on an EVA rate?

So you need to determine when you use, or could use, your energy for both the car and house. Figure out how much energy you can shift into off peak, what could be done in partial peak and what has to happen during peak.

That will tell you what your non solar usage is and using the rate tables the cost.

Now you can play the generation game, along with capital outlay costs and figure out what the kWh value is of solar. This predominantly will offset your late partial peak and early peak energy. You could build a spreadsheet of various amounts to see where the scales tip. Don't forget to add up all your costs and credits. Most of your production for weekdays will be in peak so that helps, but weekends not as much.

In my case it was only about 30% of my total load, as I was able to shift a lot of usage off peak and EVA is fairly cheap compared to the infrastructure costs. I also offset some of the costs based on moving fuel purchases to EV charging.

Of course all of this is a moving target as more solar is produced and the utilities will move the TOU bar around to follow production. If anything I think this could help in situations where AC plays an important role in your energy consumption as well as letting you do more during daylight periods vs having to wash your clothes at 11pm.:)
 
I did 80% offset based upon historic 5400kWh annual plus 3000kWh for EV travel. My system outputs 6800kWh per year. On the PG&E EV net metering, I still pay $50/year for true-up.

You can download 8760 hourly records from PG&E, predictions from PVWatts Calculator. Then build a spreadsheet to model EV vs. regular TOU rate plans with weekend/weekday and seasonal rates. My analytical model is spot on. I can do this in exchange for a referral.
 
122%! That’s my past 365 days of solar generation (19.5 MWh) as compared to my annual home use (16 MWh in 2016) when I installed my first 40 ACPV ground mount panels (10.4 kW in May 2016). But as someone mentioned, it’s a moving target. If you’re like me, you’ll add EVs and then more panels...

I bought EV #1 (Cadillac ELR) in June 2016 (8k miles per year uses 2 MWh). A few months later, I added EV #2 (Volt using the same 2 MWh of juice as the ELR for similar miles driven). Then EV #3 (MS) in Dec 2016 (used mostly for long trips with free SC). Most utilities - like mine - will limit what they allow you to install. Their grid (you’re connected to), so their rules. Just reality of electric tariffs and utility influence on state utility boards. My REC made me prove I needed more power before I could add phase two (20 additional panels equal to +5.7 kW), which I did a year later (May 2017). I could only do my solar expansion after proving a year worth of increased consumption tied to my EVs.

For those adding solar, think long term and have your panels face SW to West. This produces more PEAK afternoon/early evening kWhs that are far more valuable to the grid and you. Just a few months after my first phase of solar was installed, my Iowa REC changed the rules (their tariff). They moved to Time Of Use (TOU) prices and DOUBLED the price (from 8 to 16 cents per kWh) during their new peak time (4-9pm, 7 days/week). While I get net metering, it’s cashed out monthly (most utilities are annual true-up). The only good news is they pay me 11 cents for my excess PEAK electricity, whereas excess off-peak only pays me 3 cents per kWh.

Also, if you want REAL numbers based on my midwestern solar production, here’s what you may find very useful. My original 10.4 kW solar system produced 12.5 MWh in its first year. On my one year anniversary, I expanded my system to 16.1 kW, and it just produced 19.5 MWh over a year. Yet I installed my final 20 panels at 225 degrees Azimuth (SW facing), and I didn’t lose much, if any, efficiency for not facing the panels straight South (as all installers will say is best). It’s not best, as South panels produce peak energy at Noon, which is off-peak and for my net metering agreement, only 27% (3 vs 11 cents for excess monthly cash out from April through October) of the value.

To hyper-conserve my peak electricity usage (so I could sell back more 11 cent peak excess kWhs) I also switched out over 100 old light bulbs to LEDs (only about a buck each at Sams). So that brought my annual home energy demand from 16 down to 14 MWh. Plus another 4 MWh for my EVs is now total annual electric consumption of 18 MWh. So with my solar production in the past year at 19.5 MWh, that now leaves me at 108% of my TOTAL (home plus EVs) usage. Al Gore can have my extra 8% to go toward his private jet’s CO2 ;)
 
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122%! That’s my past 365 days of solar generation (19.5 MWh) as compared to my annual home use (16 MWh in 2016) when I installed my first 40 ACPV ground mount panels (10.4 kW in May 2016). But as someone mentioned, it’s a moving target. If you’re like me, you’ll add EVs and then more panels...

I bought EV #1 (Cadillac ELR) in June 2016 (8k miles per year uses 2 MWh). A few months later, I added EV #2 (Volt using the same 2 MWh of juice as the ELR for similar miles driven). Then EV #3 (MS) in Dec 2016 (used mostly for long trips with free SC). Most utilities - like mine - will limit what they allow you to install. Their grid (you’re connected to), so their rules. Just reality of electric tariffs and utility influence on state utility boards. My REC made me prove I needed more power before I could add phase two (20 additional panels equal to +5.7 kW), which I did a year later (May 2017). I could only do my solar expansion after proving a year worth of increased consumption tied to my EVs.

For those adding solar, think long term and have your panels face SW to West. This produces more PEAK afternoon/early evening kWhs that are far more valuable to the grid and you. Just a few months after my first phase of solar was installed, my Iowa REC changed the rules (their tariff). They moved to Time Of Use (TOU) prices and DOUBLED the price (from 8 to 16 cents per kWh) during their new peak time (4-9pm, 7 days/week). While I get net metering, it’s cashed out monthly (most utilities are annual true-up). The only good news is they pay me 11 cents for my excess PEAK electricity, whereas excess off-peak only pays me 3 cents per kWh.

Also, if you want REAL numbers based on my midwestern solar production, here’s what you may find very useful. My original 10.4 kW solar system produced 12.5 MWh in its first year. On my one year anniversary, I expanded my system to 16.1 kW, and it just produced 19.5 MWh over a year. Yet I installed my final 20 panels at 225 degrees Azimuth (SW facing), and I didn’t lose much, if any, efficiency for not facing the panels straight South (as all installers will say is best). It’s not best, as South panels produce peak energy at Noon, which is off-peak and for my net metering agreement, only 27% (3 vs 11 cents for excess monthly cash out from April through October) of the value.

To hyper-conserve my peak electricity usage (so I could sell back more 11 cent peak excess) I also switched out over 100 old light bulbs to LEDs (only about a buck each at Sams). So that brought my annual home energy demand from 16 down to 14 MWh. Plus another 4 MWh for my EVs is now total annual electric consumption of 18 MWh. So with my solar production in the past year at 19.5 MWh, that now leaves me at 108% of my TOTAL (home plus EVs) usage. Al Gore can have my extra 8% to go toward his private jet’s CO2 ;)
Can you post your daily generation?

You can track my daily progress by clicking the SolarEdge link in my signature.
 
300%+. It's going to be up there 25 years so why chain yourself to your past usage like an albatross around your neck? Plan for the future.

Once you have headroom, a lot of horizons open up.

I'd now have adjustable on-demand loads and can get in around 7 kWh left over for the day. No free-lunch for the utility.
 
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outie

Active Member
May 22, 2016
2,871
2,711
SoCal
For the last 3 years I am at 99.8%. And I have no idea why you would want or design to be only 70%
Because with TOU plans you can net zero in $$$ even though you are a net consumer of electricity. It's more cost effective to offset certain % of your actual kWh usage, even for tiered rate. You have to take into account how much you spend on the whole system and the break even time.

Look everyone. Fill your entire roof with Solar - except for the North Side.....and you will ALL produce more energy than you use.
Right, and what are you going to do with all the excess energy produced? You sell back to the grid at wholesale price. It's very cost ineffective to do that because you paid a lot for the system you don't actually use. But hey, not every one does everything in the most cost effective way. Your money, your choice.
 
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miimura

Well-Known Member
Aug 21, 2013
7,203
7,156
Los Altos, CA
When I had my house built 5 years ago, I tried to get into a special rebate program called NSHP. I could have had a 9.8kW system for $1/watt net cost. However, the paperwork was beyond what our solar installer was willing to do since it incorporated extensive Title 24 calculations and higher performance for the whole home. In retrospect, I should have paid a consultant to do the extra work required before the walls were closed up because I ended up with a house with builder-grade insulation and poor envelope performance. The 4.3kW system that I could afford at the time is perfect to offset the electric cost of running the house. However, it does not cover charging our cars.
 
Because with TOU plans you can net zero in $$$ even though you are a net consumer of electricity. It's more cost effective to offset certain % of your actual kWh usage, even for tiered rate. You have to take into account how much you spend on the whole system and the break even time.


Right, and what are you going to do with all the excess energy produced? You sell back to the grid at wholesale price. It's very cost ineffective to do that because you paid a lot for the system you don't actually use. But hey, not every one does everything in the most cost effective way. Your money, your choice.

wrong answer.

you never know what will come along....like buying another Tesla. Then you won't have to go back up on the roof to do anything.. OR convert your appliances to electric from gas. The point is......to not have to go back up on the roof for anything. Oh wait....I suppose that most people won't install their own system as I did.
 
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