Issues with PV/Batt/Net meter grid tie

[Sunking]

Almost as calm as it gets when you go on vacation. I miss those days.

That would be green with envy speaking.

[Murby]

I've been trying to get a system installed on my place for several months now. This is to be a 10Kw-12Kw system (depends on panel output and geometry as to what can fit) with battery backup, ideally Powerwall2 x3 if they are out. The parameters are it needs to be hooked to grid for net metering. This requires upgrading the incoming service from a 150a to 200a (but since there are several loads being added, it will be to 400a, 2x 200a wires). I've had a couple bids from some smaller installers that were ok but not with the panels I'd want (older, less efficient, maybe made in China - had experience with those, won't go there).

I'm not sure if I understand this. Why do you need to upgrade from a 150a to 200a service? The solar system makes power, it doesn't suck it in..

Basically comes down to Solar City vs a Sunpower installer.

Solar City the issue is getting the peripheral work tied into the project so it can be done under one loan, and for the 30% tax credit. The overall cost is about $56k with credit puts it right about $40k cost. However, they won't put the cost of the service upgrade from the utility to the project, meaning I have to pay out of pocket and possibly miss the tax credit on that portion. The panels are decent, Panasonic with around 19+% efficiency, but their geometry limits me to 10Kw and they do not install other than on the roof - no ground mount, outbuildings or porch roof.

Sunpower has higher efficiency panels 22+% that with the geometry would allow 12Kw on my roof, they will roll the utility upgrade into the project (can't net meter that size array without it) - but aside from a roughly $5k higher cost for the system, if I finance with a solar loan they tack on 15-19% more to the project cost making it just not practical. I notice Sunpower recently took a hit on sales & stock. Maybe they want to rethink that loan penalty, they'd have made another sale if it weren't for that.

Anyone know of a lender that gives a low rate that doesn't charge back to the installer?

What difference does it make to SunPower where the money comes from for the project? That doesn't sound legit unless they're the ones providing the financing..

I have to say, it doesn't sound like you're doing your homework on this.. either that, or there are issues to consider that I'm not aware of. A 10kw to 12kw system is not that big...

[ButchDeal]

What difference does it make to SunPower where the money comes from for the project? That doesn't sound legit unless they're the ones providing the financing..

I have to say, it doesn't sound like you're doing your homework on this.. either that, or there are issues to consider that I'm not aware of. A 10kw to 12kw system is not that big...

Sunpower is providing the finance in this situation.
a 10-12kw system is definitely on the large size for residential. Some power companies do not allow more than 10kw and many have different rules for more than 10kw.

[SunEagle]

I would also think that going to a 12kw system would generate 50Amps at 240v which is 33% of a 150amp service and exceeds the allowed % to backfeed into your main panel.

Of course the local codes always take precedent over the NEC so as Butch states the POCO may be setting the rules.

[Murby]

Sunpower is providing the finance in this situation.
a 10-12kw system is definitely on the large size for residential. Some power companies do not allow more than 10kw and many have different rules for more than 10kw.

My power company, Detroit Edison, considers anything under 20Kw to be small residential. A friend of mine, who doesn't have solar, chews through $550 worth of electricity every month.. Haven't done the math, but I believe that would be up there around 20kw if not more..

[ButchDeal]

My power company, Detroit Edison, considers anything under 20Kw to be small residential. A friend of mine, who doesn't have solar, chews through $550 worth of electricity every month.. Haven't done the math, but I believe that would be up there around 20kw if not more..

thats wonderful, though anecdotal. 20kW is just the limits that DTE has set as Category 1 for the application process.
https://www2.dteenergy.com/wps/porta...vZ0FBIS9nQSEh/

So as a quick example here is one for Central Maine Power, that has residential as less than 10kW. Anything larger and you need additional insurance and longer install procedure etc.

http://www.cmpco.com/YourAccount/puc324.html

The average size of a residential solar install is around 6kw.
As I stated some power companies will not allow anything over 10kw. Most required additional insurance and special considerations for systems over 10kw.
Pretty much anything over 10kW is going to need something other than a load side tap (a breaker in MSP), something like a line side tap.

[Murby]

Pretty much anything over 10kW is going to need something other than a load side tap (a breaker in MSP), something like a line side tap.

Why is this? 10kw is only ~40 amps being fed back... My welder draws that much.

[ButchDeal]

Why is this? 10kw is only ~40 amps being fed back... My welder draws that much.

A welder doesn't back feed

It is actually the inverter.
you can connect 10kW to a 7.6kW inverter which needs a 40a back feed breaker.
You can fit a 40 a back feed breaker on a 200A MSP that meets the 120% back feed rule (200a X 1.2 - 200a = 40a)

as I stated you can use other methods to get more power back fed in but they have added costs etc, like a line side tap, or MSP main breaker derate, or MSP with higher rated bus.
These are not typically already in the house so require additional work.
In this case the OP is looking to upgrade the service as well as the MSP..

[Murby]

A welder doesn't back feed

It is actually the inverter.
you can connect 10kW to a 7.6kW inverter which needs a 40a back feed breaker.
You can fit a 40 a back feed breaker on a 200A MSP that meets the 120% back feed rule (200a X 1.2 - 200a = 40a)

as I stated you can use other methods to get more power back fed in but they have added costs etc, like a line side tap, or MSP main breaker derate, or MSP with higher rated bus.
These are not typically already in the house so require additional work.
In this case the OP is looking to upgrade the service as well as the MSP..

Excellent.. Thanks for the answer.. I was going on pure math and ignoring NEC rules.

[ButchDeal]

Excellent.. Thanks for the answer.. I was going on pure math and ignoring NEC rules.

yep. This is exactly why the Solaredge EV charger is so nice. Not only does it save on install it saves on breakers and other rules that might push an MSP or service to have to be upgraded.
The Inverter itself becomes the charger so no need for any other breakers, or more capacity.