Can I get some last minute advice before signing contract?

[hayhayday]

If the storedge is a energy hub inverter allows ratio of 2 as the excess power over 7.6kw can still be used to charge the batteries rather then being clipped so one inverter should be ok as it should reduce\eliminate clipping.

[mikedunkel]

Glad we could help. Do you plan to have the generator integrated with the solar system though the Backup Interface that is shown in the SolarEdge diagrams?

I made it clear to the installer that I expect a fully integrated system. He hasn't gotten back to me with specifics so maybe somebody here knows. Is the system smart enough that in the event of a grid outage but full sun, the generator will back down or completely turn off if the solar is handling the loads?

[sabersix]

Thanks for your replies, I asked my installer and he is going to do something between a 50/50 and 66/33 split, my house is oriented 45 degrees off true north so I'll be getting panels on the SW and SE roof. I called and finalized the order, I really appreciate the tips and advice as they directly led to me removing the 2nd battery and instead getting the generator. Total cost will be reduced about $2k and the system will be a little better at doing what I want it to do.

Glad we could help. Do you plan to have the generator integrated with the solar system though the Backup Interface that is shown in the SolarEdge diagrams?

[mikedunkel]

Typically you oversize in the 1.2 range. This is over 1.5. Anything over 1.3 and you essentially hit diminishing returns. For a 7.6 kW inverter I would be looking at around 9.1 kW worth of panels. Now, unless because you are doing a battery, there is something special that the battery needs that can justify that oversizing. Shading or odd roof peaks may justify this too. Otherwise, you could save a good chunk of money.

I think SolarEdge allows a max of 155%. It almost seems like your installer is just going for the max here???

As noted though, if you have some sort of split array in multiple directions, then I would not worry about it.

Thanks for your replies, I asked my installer and he is going to do something between a 50/50 and 66/33 split, my house is oriented 45 degrees off true north so I'll be getting panels on the SW and SE roof. I called and finalized the order, I really appreciate the tips and advice as they directly led to me removing the 2nd battery and instead getting the generator. Total cost will be reduced about $2k and the system will be a little better at doing what I want it to do.

[mikedunkel]

Is that $15k price for the generator, fuel tank and installation?

If so that is really not a bad price depending on the size fuel tank and kw rating of the generator.

I already have a buried LP fuel tank with lines running to the house. I had previously received a quote for a stand-alone generator which duplicates a lot of the safety wiring they are planning on doing for the solar install anyway, and that quote was under $10k.

EDIT: and I just got an email from my installer, the price was incorrect. New quote is $8k for a 14kw generac + whatever it costs for me to have someone come to the house and connect the generator to the LP which I doubt would be more than $300-$500.

[SunEagle]

Thanks for these inputs, they are very helpful. He came back with the generator quote and something is amiss -- $15k for a generac generator!!!! The most expensive residential application is only $5700 and the 10KW which should be sufficient for my needs is about half that. The 48kw commercial generator is about that price so I think there was an error in the quote.

Is that $15k price for the generator, fuel tank and installation?

If so that is really not a bad price depending on the size fuel tank and kw rating of the generator.

[mikedunkel]

Thanks for these inputs, they are very helpful. He came back with the generator quote and something is amiss -- $15k for a generac generator!!!! The most expensive residential application is only $5700 and the 10KW which should be sufficient for my needs is about half that. The 48kw commercial generator is about that price so I think there was an error in the quote.

[theoak]

Typically you oversize in the 1.2 range. This is over 1.5. Anything over 1.3 and you essentially hit diminishing returns. For a 7.6 kW inverter I would be looking at around 9.1 kW worth of panels. Now, unless because you are doing a battery, there is something special that the battery needs that can justify that oversizing. Shading or odd roof peaks may justify this too. Otherwise, you could save a good chunk of money.

I think SolarEdge allows a max of 155%. It almost seems like your installer is just going for the max here???

As noted though, if you have some sort of split array in multiple directions, then I would not worry about it.

[solarix]

I'm not a fan of 11.3 kW of panels on a single 7.6 kW inverter.

If you put at least a third of the 11.3kW array at an orientation that is at least 90deg different in azimuth from the main array, there will only be a few days of the year when "all the stars align" and you will get a bit of clipping. The inverter is always going to protect itself from an oversize array by setting the operating voltage to something non-optimum - so you are not going to hurt the inverter no matter how big the array is. I design a lot of systems to be larger than 10kW on a 7.7kW inverter with no problems. With the utility going away from net metering, we have to go with bigger arrays to compensate (no problem now that PV panels are so affordable), but the 20% backfeed rule in the Code is a real hindrance to large systems. By "overpanelling" the inverter, large systems can be done without having to do dual inverters and expensive service panel upgrades.

[sabersix]

Can you elaborate? The local company said the inverter is speced to handle 150% of its rated power.

You will get some clipping with the smaller inverter as it will not go much above 7.6 kW. You system is effectively a 7.6 kW system. There is really no point to 11.3 kW worth of panels unless you are in a sub-optimal solar location (which doesn't seem to be the case for GA). You should reduce the number of panels and save even more money.

On the other hand, two 7.6 kW inverters is way overkill for 13.1 kW of panels. You will probably only get 11 kW peak out of those panels. Have you run a solar calculation using PV Watts https://pvwatts.nrel.gov/ for your area?

[mikedunkel]

I'm not a fan of 11.3 kW of panels on a single 7.6 kW inverter.

Can you elaborate? The local company said the inverter is speced to handle 150% of its rated power.

[theoak]

I'm not a fan of 11.3 kW of panels on a single 7.6 kW inverter.

[J.P.M.]

Not sure if you saw my OP but Tesla is already out of the discussion, the only reason I mentioned them was to show that 1 system turns off when the grid goes down and a 2nd does not. I agree 100% with your sentiments about local companies and those were a significant factor in my decision. I asked the local vendor to requote me the smaller system, eliminate one of the RESU16 batteries, and replace it with an LP generator that could run all my big ticket items. Since they have to do all the electrical rewiring anyway, I suspect the generator will be a lot less expensive (and probably more effective) than the 2nd inverter and battery.

Understood. I missed the Tesla removal. My bad.

Good luck.

[mikedunkel]

I'd start by removing Tesla from consideration. Sounds/Reads to me like even though cost may not be your primary consideration,../...
Your goal of full power outage operation is certainly a choice, but it'll likely increase system acquisition costs by a significant amount. Depending on how often, or your angst for power outages, my guess the cost of perceived safety may be higher than you might anticipate.
I'd size and price a system with and without the emergency load considerations and decide if the cost differential is worth it to you. If not, I'd consider getting serious about your push come to shove plans and revise your emergency load criteria.
One usually cost effective approach and an adjunct to serious emergency load reduction is a generator.

Not sure if you saw my OP but Tesla is already out of the discussion, the only reason I mentioned them was to show that 1 system turns off when the grid goes down and a 2nd does not. I agree 100% with your sentiments about local companies and those were a significant factor in my decision. I asked the local vendor to requote me the smaller system, eliminate one of the RESU16 batteries, and replace it with an LP generator that could run all my big ticket items. Since they have to do all the electrical rewiring anyway, I suspect the generator will be a lot less expensive (and probably more effective) than the 2nd inverter and battery.

[J.P.M.]

Its more about the inverters than the system size. The difference in cost between panels in 11.3 and 13.1 isn't that large but the 2nd inverter adds quite a bit of cost. I'm just not convinced that a single 7.6 KW inverter can handle 2 3-ton air conditioners, 2 refrigerators, freezer, well pump, microwave, and all the miscellaneous lights, fans, and outlets my family uses on a day to day basis. Obviously I'll be able to manually manage some of this if push comes to shove.

A weather event can certainly take down power lines, but those lines often stay down longer than the weather event. A thunderstorm or tornado can be over in 30 minutes and the remains of an ice storm can melt the next day (I live near Atlanta) but power has been down for as long as a week (heck, I think parts of TX were down for 2 weeks this past winter). The batteries will get me through the initial event and night time and depending on WX forecast I can prioritize the food storage over creature comforts as required.

I'd start by removing Tesla from consideration. Sounds/Reads to me like even though cost may not be your primary consideration, I bet most bang for the buck is, and that includes equipment and installation quality considerations. Staying with local, quality, established vendors is as important a consideration as equipment quality. You'll get neither with Tesla.
After that, and before I made any decisions on which of the remaining vendors to choose, and even though it'll be a bit of a SWAG, I'd get a better handle of expected annual load, and if you havn't done so already, as well as getting a plan for how to reduce your emergency power outage load, starting with living without or greatly reducing the big draws for A/C while the power is out. Doing both those things will perhaps reduce not only your array size but also maybe reduce your excess generation which seems to be a somewhat secondary goal.
Your goal of full power outage operation is certainly a choice, but it'll likely increase system acquisition costs by a significant amount. Depending on how often, or your angst for power outages, my guess the cost of perceived safety may be higher than you might anticipate.
I'd size and price a system with and without the emergency load considerations and decide if the cost differential is worth it to you. If not, I'd consider getting serious about your push come to shove plans and revise your emergency load criteria.
One usually cost effective approach and an adjunct to serious emergency load reduction is a generator.