brucet999
Active Member
SCE pays a measly $0.02 per kWh for end-of-year overage, but they charge at retail rates for consumption in excess of what you export.
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Is my solar panel system too big?
- Thread starter Carbonfiber
- Start date
Silicon Desert
Well-Known Member
I don't know about Tesla modules, yet I doubt they are much different than many others. I am referring to industry quoted percentage loss of the life of the modules and much of the loss comes at a higher rate in earlier years for many modules. Of course it depends on the type of panel and manufacturer..
brucet999
Active Member
Yes, industry average is pretty bad. Most panels lose 2% to 3% in the first month to LID (light induced degradation) and then degrade .%5 per year thereafter. High quality panels like Panasonic HIT and SunPower Maxeon have no LID losses and less than 0.3% annual degradation.
It is going to take longer to get to the break even point I think. When we installed our system about 2.5 years ago (paid cash), I calculated that instead of paying SCE for the electricity every month, if I pay myself back the same amount back, it will take 4.5 years to fully pay myself back. After that, my system is "paid" off and I got my money back. From that point on, it is pure saving.
Now if I have to do the calculation, I don't know what it would be. On one hand, the system is MUCH cheaper now. On the other hand, the TOU rates are way worst so I will need to get a bigger system to compensate. I am beginning to think it may be better to just get Powerwalls and let other people make energy for you. Just store the batteries when SCE is selling other people's solar to you for cheap and use them in the evening. I think it is called TimeShift? And Powerwalls will help with these newly developed PSPS events!
Base on your explanation and calculations for my specs, I should see my money back in about 6 years assuming I break even each year with the solar panels.
I also paid cash.
At the time when we got solar, it was about saving money. But now that we got it, it does feel pretty good that our house and cars are powered by the sun.
Doesnt work that way. Powerwalls only store your own generated solar power, they dont charge from the grid unless in stormwatch mode. This is a tesla limitation. There appears to be a somewhat "hacky" way around it by changing settings in the installer interface end user are not supposed to mess with.
I thought you could charge it from the grid if you don't have any solar panels. You don't get the tax credit, but I think you could charge from grid because there is no other way to charge the battery right? And having Powerwall will qualify for TOU-D-Prime, so as long as your battery is enough to power thru the evening, so you will be paying at $0.16 to $0.17 / kWh anytime. And that rate will go down as more and more people are getting solar. Also powerwall prices will go down too. So I think this could be the way to go.. just get battery and let other people generate solar and lower the rate for you.
Currently Tesla is installing Q.PEAK DUO BLK-G6+ 340W. They guarantee 98% for the first year, and degrade <0.54%/year after that. The Panasonic HIT 340W panels guarantee 97% for the first year, and <0.26%/year. So until year 9, the Q.PEAK panels would generate more power, but the HIT panels would be ahead from there on out to 25 years. Averaged over the lifetime, HIT will produce 2.3% more power. The HIT panels need 7% less roof area to generate the same nominal power, and lose 0.26%/C versus 0.36%/C as a function of temperature. Q.PEAK panels have a half cell architecture that may provide some advantage when the panels are partially shaded.
So HIT panels are somewhat more efficient but they cost $1/watt versus $0.70/watt for the Q.PEAK panels. If an installation is short on roof space, the HIT panels may be the better choice; otherwise the price differential pretty much swamps the perhaps 5% difference (degradation plus temperature induced losses) in power generation. One can install more Q.PEAK panels for the same cost, especially if one uses a string inverter with mid circuit interrupters. I suppose that if one is using a microinverter-based system, then the cost per panel including the microinverter will reduce the advantage of the Q.PEAK panels.
Its true (of course) that you can charge from the grid if you dont have solar. Since you have solar, i took your post to mean "with solar" but re reading it again, thats not what it says.
Silicon Desert
Well-Known Member
yes, I have LG modules on one home, and Panasonic on the other and I see not that much loss after 5 years on one system and 10 years on the other.
Yes, it is worth it.
First, the California electricity tariffs are significantly higher than other states and the main financial advantage is to stop paying those tariffs. The NEM2 tariffs allow for 1:1 offset for each category TOU (winter peak, winter off-peak, summer peak, summer off-peak for TOU-C and winter partial-peak and summer partial-peak for EV2-A). If you send back at least as much energy as you use then you are only paying the minimum daily charge (MDC) of $0.32854/day or $119.92/year. When you are pulling from the grid when the sun is down there is a charge of $0.0207/kWh in non-bypassable charges (NBC) which allows you to pull 5,793 kWh yearly from the grid before you exceed the yearly MDC total. The wholesale rate of $0.02-0.03/kWh for exceeding your usage is a bonus on top of the savings, also if you are with a Community Choice Aggregator (CCA) like Silicon Valley Clean Energy (SVCE) they may buy back any excess at retail rates of $0.06-0.08/kWh. Based on my past years of usage, a 8.16kw panel array and 2 Powerwalls, I will be saving $1,850/year and the system will pay for itself 13 years or 6.6 years if I didn't have the Powerwalls installed.
Second, having solar plus Powerwalls provides peace-of-mind here in earthquake country and the era "public safety power shutoffs" when we might lose power multiple days.
charlesj
Active Member
brucet999
Active Member
Yes, more than enough to offset annual usage, but SCE still zings me $10/mo plus minimum usage fee.
charlesj
Active Member
Well, that is what I pay to PG&E but my local community power provider pays way more for excess generation than PG&E and brings that down to about half, the the carbon offset the other half and then some for gas.
brucet999
Active Member
Jae001
Member
In my opinion you can never have too much power. You never know when you will need it. I got a 12.24kW system and never thought I would use all of it but I was wrong. 6 months later I got a heat pump for my pool and used it everyday to heat my pool using electricity from the solar panels. This heat pump is a monster using more power than charging my car. Now a year later my wife wants to get a Tesla and now we are going to need more power. Lastly we want a spa and these take a lot of power as well. So you just never know what will come up in the future where you will need more power. If you don't use all the power you can get a lot of credits built up for the rainy winter months that will keep your electricity bill at zero.
charlesj
Active Member
Called something like that. Besides the higher pay for excess, I think PG&E has something like that, been getting $60 or more a year.
I don't ask, just take the credit.
system 11,655watt (DC) derated to 9,907watt (AC) Tier 1 in Florida is under 10,000
(supposedly lots of paperwork for tier 2 producers, insurance etc etc)
produced 17,200kwh in 2019
produced 17,400kwh in 2020
pool, AC, small PHEV, all electric house, led’s etc.
i use about 55% roughly of that, around 9,000/yr.
old, non-ratcheting electric meter would spin backwards or forwards
so 100% credit overproduction
new “smart” meter
they “pay” me a fraction over 2 cents per kwh i send them
I buy it back at night for about 8.3 cents per kwh
minimum bill $21.69 connect fee
new pool heater massive draw so ate up all my overages and way more.
need to upsize PV array 3-4kw minimum to cover pool heater.
oversize the array to the maximum you can reasonably afford, it will come in handy, especially if VPP’s start appearing and you can join (Virtual Power Plants)
Australia seems to be going “all in” on PV plus batteries.
7,800 megawatts proposed with over 500 megawatts online since Hornsdale plant went online in late 2017
https://www.theage.com.au/national/...ape-the-electricity-grid-20210211-p571qm.html
also Tony Seba
(supposedly lots of paperwork for tier 2 producers, insurance etc etc)
produced 17,200kwh in 2019
produced 17,400kwh in 2020
pool, AC, small PHEV, all electric house, led’s etc.
i use about 55% roughly of that, around 9,000/yr.
old, non-ratcheting electric meter would spin backwards or forwards
so 100% credit overproduction
new “smart” meter
they “pay” me a fraction over 2 cents per kwh i send them
I buy it back at night for about 8.3 cents per kwh
minimum bill $21.69 connect fee
new pool heater massive draw so ate up all my overages and way more.
need to upsize PV array 3-4kw minimum to cover pool heater.
oversize the array to the maximum you can reasonably afford, it will come in handy, especially if VPP’s start appearing and you can join (Virtual Power Plants)
Australia seems to be going “all in” on PV plus batteries.
7,800 megawatts proposed with over 500 megawatts online since Hornsdale plant went online in late 2017
https://www.theage.com.au/national/...ape-the-electricity-grid-20210211-p571qm.html
also Tony Seba
