Less likely to need a new panel these days. Power Control features are becoming more and more common to avoid the need a panel upgrade. Basically Powerwall system is smart enough to avoid sending more power to the load center that it is rated for.
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What do I need to know? Tesla Solar + Powerwall Install
- Thread starter Jeremy3292
- Start date
After doing more research, I came to this conclusion
I need to account for degradation of the panels (efficiency loss) over time and also like you said it is good to have a few extra panels than you think you may need.9.6 kW solar panels (I may go up to 10 kW) also provides for a great DC/AC ratio with the standard 7.6 kW inverter on Powerwall+, keeping any potential clipping to a minimum. It is also good to ensure your inverter is at "max capacity" as often as you can or so I've read. My simple understanding is if your inverter is only 7.6 kW, then you will never get more than 7.6 kW delivered to your house at any given time, regardless of how many solar panels you have on your roof - e.g. it is the bottleneck or limiting factor.
I found out Duke Energy requires all solar customers to be on time-of-use billing as of 1/1/23, which furthers the need for 2 Powerwall's. This will give me a whole home backup but will also help ensure I am not pulling from the grid during peak times. The minimum bill is $30 per month (which seems high, ugh) before any net metering credits are applied, but the net metering is not so great at $0.026 cents per kW.
charlesj
Active Member
Now you are getting there. Did you expect the power company to treat you well?After doing more research, I came to this conclusion
9.6 kW solar panels (I may go up to 10 kW) also provides for a great DC/AC ratio with the standard 7.6 kW inverter on Powerwall+, keeping any potential clipping to a minimum. It is also good to ensure your inverter is at "max capacity" as often as you can or so I've read. My simple understanding is if your inverter is only 7.6 kW, then you will never get more than 7.6 kW delivered to your house at any given time, regardless of how many solar panels you have on your roof - e.g. it is the bottleneck or limiting factor.
I found out Duke Energy requires all solar customers to be on time-of-use billing as of 1/1/23, which furthers the need for 2 Powerwall's. This will give me a whole home backup but will also help ensure I am not pulling from the grid during peak times. The minimum bill is $30 per month (which seems high, ugh) before any net metering credits are applied, but the net metering is not so great at $0.026 cents per kW.
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That DC/AC ratio is not that great with either of those numbers so you will not see much clipping at peak summertime.
Yes, with time of use, more battery is needed as that is the time, dinner time, when a lot of energy is needed.
I happen to have community power that pays around 6-7 cent a kWh excess generation at True Up time. Minimum bill is around $11+/-.
You need to work on the state to allow this kind of community organization that buys and sells the electricity.
NoNow you are getting there. Did you expect the power company to treat you well?
Ironically South Carolina has a 25% state solar tax credit, which is one of, if not the best in the nation.I assume you meant that DC/AC ratio "is great" as I won't see that much clipping at peak summertime? Per the PVWatts calc it looks at either 9.6 or 10 kW clipping is virtually nonexistent with the 7.6 kW inverter in my area.
My understanding is that I would want higher PV wattage than inverter wattage, especially with TOMU billing, so I can squeeze out all the solar power towards the end of the day and during the morning hours in the winter (peak TOMU hours).
If I had 10 kW panels operating at less than peak, say 76% towards the end of the day (or beginning), well that is still a full 7.6 kW being delivered vs if I had 7.6 kW panels operating at the same 76%, that is <5.8 kW being delivered. (I hope I'm doing this right!)
They just changed it 1/1/23 (at least for Duke Energy) after they got approval from whatever state board to be very anti-solar friendly. The <$0.03 cents payback per kWh plus TOMU billing really just kicks you in the butt. The only good news is the $30 bill minimum is before any excess net metering credits are applied. My guess is I'll likely have plenty of excess credits during the day (off-peak) but I'll need to rely on the 2 Powerwall's for home energy consumption during that 6pm-9pm window and 6am-9am window during the winter as I have all electric heating and cooling.
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charlesj
Active Member
No
I assume you meant that DC/AC ratio "is great" as I won't see that much clipping at peak summertime? Per the PVWatts calc it looks at either 9.6 or 10 kW clipping is virtually nonexistent with the 7.6 kW inverter in my
My understanding is that I would want higher PV wattage than inverter wattage, especially with TOMU billing, so I can squeeze out all the solar power towards the end of the day and during the morning hours in the winter (peak TOMU hours).
I meant that clipping is good but that 1.2/1.3 ratio is not much at all. With more panels or higher wattage panels where you'd get 1.4 /1.5, your system would ramp up earlier, stay at peak production of 7.6 kW longer and fall off later with overall daily production more with same inverter versus that 1.2 ratio.
You'll have to figure this out if 2 battery's will fill your need with all electric. It may help reducing peaks as some locations charge more for peaks even inside a high peak period.
Will all the tax credit you are offered, I'd be on the camp of get as much panels and batteries as you can afford. Assuming you don't move, you probably will never update this system again and utilities will cut back on incentives I feel as more folks go solar in your area. This includes changing NEM terms like CA/HI and your overall energy use will be higher as time goes on in terms of rates and adding EVs, etc.
The tax credits just looks like free $$ left on the table so it makes your install so cheap really.
The tax credits just looks like free $$ left on the table so it makes your install so cheap really.
Agreed 100%. Cash flow up front is the only thing as it’s $40k cash with the tax credit cash coming later after filing my return, but I’ll likely just withhold a lot less from my paychecks so I can “take the credit” throughout the year. Not taking a loan to buy solar panels. Also SC limits the tax credit to $3,500 per year with a 10 year carry forward. So I’ll get all the money back it just takes a few years.
I’m unsure of how much electricity I’ll use with the heat pump as my current house has natural gas like I said. I’ve been doing some math based on my current house sq footage and usage, but I’ll need some power bills at the new house to really know for sure. Doesn’t usually get lower than 25-30 degrees at night during the winter here, so the heat pump should be very efficient.
I feel like 10 kW solar panels + 2 Powerwall’s seems like plenty for future proofing but we will see.
Fun fact Tesla dropped the price of solar panels 3% overnight, at least in my area. $932 vs $960 per panel.
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JJ - if my wall connector is on the non-backed up loads side and the grid is ON and my Powerwall's are charged, would any excess solar output be sent to my wall connector to charge my car (and then back to the grid if still excess)?
If the grid is OFF the non-backed up loads side still receive no power even if there is excess solar output? So I couldn't charge my car with the grid OFF, period?
Additionally, if you have 2 Powerwall's and the grid is OFF (or even when the grid is ON), what is the order of operations for power use?
- Use all solar power available to power house
- Use all Powerwall energy available to power house
- Does it drain each Powerwall simultaneously or one at a time?
- Use grid power if grid is ON, no power left if grid is OFF (hypothetically)
Can't you tell Duke to come get their meter?
This $30.00 sounds more like extortion than anything.
I could if I went truly off grid probably. I think I will get lots of net metering credits during the off peak hours, so that should lower my bill a lot (hopefully). Only use the Powerwalls during the 3 hour on peak window to avoid any of those peak charges. In the summer the on peak 6-9pm window is still a good amount of daylight also so I should still be generating solar then also.
I'm probably ok with $15 of the $30 minimum, as that is the facilities charge everyone has to pay to have access to the grid. So from there they are saying I basically need to use $15 worth of energy each month, which definitely is shady especially with the TOMU periods. But hopefully my net metering credits can bring that down to a $15-$20 total bill.
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I would skip power wall. It is a luxury, and I’d rather have more panels than a battery for the money, you can use the grid as a battery.
Why? They still have to pay for the maintenance of distribution even if you aren’t using it….
Sorry, just seeing this.
In most cases, yes you could use solar to charge the car if you wanted to in this scenario, provided there was a CT on the circuit that had the car on it, so the gateway could see it. "Any excess solar going to charge the car" isnt quite how it works, but if there is a CT monitoring the load on the non backed up load side, "The system" can provide power to it.
Note that there is no "match the load to the solar output" happening when ON grid, at least not through anything Tesla has setup itself The gateway can send power to the non backed up loads provided they are monitored with a CT / CTs, but its not going to match the car charging to the excess solar output. Its just going to send power to that load, with the balance coming from the grid if its not enough to charge at the rate the car is set to charge at (again this is ON GRID).
Grid OFF = non backed up loads get no power, correct. So, correct, you can not charge your car if its a non backed up load and the grid is off, unless you plug the mobile connector into an outlet thats on the backed up side.
This depends on what mode the tesla app is in. In self powered, the solar goes to power the house first, then fill the batteries, and any excess (if any) is sent to the grid. In Time based control mode, what happens depends on multiple factors, including how you have the utility buy / sell price set, etc.
jgleigh
Member
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GregBallantyne
Member
I would advise to max out both generation and storage capacity as much as feasible. You'll regret not going for whole house backup, which for you sounds like 3 PWs minimum with twice that planned generation, if the roof will carry that. Once you start down this sort of path, you see possibilities and goals you did not think of going in. With that much tax credit, you can try adjusting withholding now and avoid trading money now for money back, improving the cash flow side. It's a little tricky sometimes getting that balance, but worth it in the end. Your idea of "plenty for future proofing" today can turn into "bare minimum, should have got more" fairly easily.
BTW, I've got a 30 year old 200A load center and a 60A wall connector, and with whole a house backup installation with Tesla Gateway that panel didn't get touched, except to feed it from the Gateway rather than the grid. Partial backup gets into more panels and affects your main load center. You actually remove circuits from the main panel and add a backup panel. Adds cost.
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