Panels, Batteries and Inverter are all in the shop. Lighting, outlets, sprinkler system pump and well pump will be run off the sub panel in the garage. House isn't here yet but will have a 200 amp panel though we will not use anywhere near that much electricity.

I am thinking (be worried) that there should be a junction type box that sends power to both locations. Need power in the shop while waiting for the home and is a hundred foot run so feels wasteful to run the power to the house then back to the shop.

Need to get the permit in and my electrician is not responding.

Electrician got back to me, 200 amp panel in the shop. My well pump is a Grundfos SQF-11 made for alternative energy, so not a big draw. The fire sprinkler pump is a different animal all together.

  • 2
    Welcome to StackExchange. Would love to sink my teeth into this problem. However solar systems like this come in many varieties, and yours is complex, with long distances and mains voltage panels. Your question has one paragraph (a scant 3 lines) describing your system. A helpful answer is impossible with so little information. It would need to be on the order of 20 of those paragraphs, some fairly meaty, likely with attachments or photos. If you can provide that we can help. Sep 20 '18 at 17:46
  • First things first: are the house, shop, and garage all separate structures, or are any or all of them attached to each other? Also, when you say "sprinkler system pump", are you talking about a pump for a fire sprinkler system, and if so, is your system under NFPA 13D rules, or...? Sep 20 '18 at 22:25
  • Furthermore, how many HP is the sprinkler pump, and are you planning on having a fossil fuel generator as part of the system? If you do have a genset, is it going to be a portable you have to plug in, or a fixed standby generator hard-wired into the system? Sep 24 '18 at 23:34
  • One other thing -- does the shed already have an electrical panel in it? Sep 25 '18 at 22:48
  • How many HP is your fire sprinkler pump, and how many spaces does the 200A panel in the shop have? Dec 11 '18 at 4:44

The correct solution here is a smallish electrical panel

Were I in your shoes, I would have a small-ish electrical panel (8 or 12 space, 200A bussing) in the shed to provide a home for the service disconnecting means -- having rule-of-six shutoffs here due to the multi-building nature (presuming the garage is attached and the shed separate) of this system. The inverter can feed a main breaker or backfed main in the panel for now, and when the house is ready, the main breaker can be removed, using main lugs to feed the panel and allowing separate shutoffs for the house and shed.

If you want a single-main-disconnect solution -- that's possible as well, using an 8-space 200A panel with feed-thru lugs (called a "mobile home panel" sometimes). The main breaker is fed from the inverter, while the feeder to the house is tapped at the feed-through lugs, and the shed circuits fed from the panel breakers, or a subpanel on a feeder breaker there.


If you want to run it on PV, you're going to pay a LOT for panels and inverters: 100A@220V = 22kW, remember that motors have start-up current that often are 5x the nominal current (so just to start a 3kW well pump you need 6kW from the supply), so just to run the well pump yu'll need at least 8kW (panel efficiency will decrease with time, inverter isn't 100% efficent, pump motor has low cos-phi, usually around .75, and also sun won't be always at the zenith).

Also cable will be a cost: the longer the run the thicker the wire (a 2,5mm^2 copper wire will bring 4kW at 10 meters, to bring the same 4 kW at 100m you'll need a 20mm^2 wire). I don't know there, but here thick (16mm^2) copper wire is pretty expensive, in the range of 2.5€/m

My suggestion is to opt for a in-place exchange, at least here, you can draw from the grid what you need and push to it when you're overproducing. Also the self-consumption grants an incentive, so you earn more money for the kW you produce and use then for pure sale. Doing this you can size your panel to 'average' need instead of peak need leading to big save on panels.

  • 1
    This is not an answer to OP's question at all. It is an over cautious handwringer to the effect of "solar is sooo expensive", and seems like maybe a splash of "this is beyond my skill level so maybe it's beyond yours". A bit patronizing. Also, you presume grid power is even available. The name of the county should warn you that you're in the Big West, where the counties can be bigger than England, have 800 residents and you have to drive 3 hours to the DMV. Sep 21 '18 at 0:06
  • @Harper -- Butte County isn't too bad -- about 200k-odd residents, mostly clustered into the small cities of Chico, Oroville, and Paradise. The Feather River Canyon area is known for quite rugged terrain though.... Sep 21 '18 at 3:07
  • Yeah, I just looked it up. What I say does apply to the non-urban sides, where you'll havea a paved road up a canyon and then jeep trails miles and miles off into the hills. A lot of beautiful places to build homes where you'd have a $200,000 ticket to get a pole line out. That'll buy a lot of PowerWalls. This being the other problem, this answer's wisdom is dated, 10 years ago I'd have nodded my head but today, the options are so much more favorable. Sep 21 '18 at 3:18
  • @harper I taught you have same kind of 'universal service' we have in Europe (Italy) where, if you build a home, you only have a fixed fee to pay to the utility to bring electricity (190€) + variable part based on the maximum power you ask for (70€/kW) + 30€ of taxes, so you can be on an alpine peak and, if you build a home for 'permanent residence', you get electricity for the same price (around 500€ for average connection) you get if you live in a condo in Milan centre, just because basic electric service here is a right, not a privilege.
    – DDS
    Sep 21 '18 at 7:39
  • @DDS difference being in Europe you will never be able to buy the land or never get a permit to build on that alpine peak, and the impracticability of provisioning utilities will be part of the reasoning for denial of permit. Whereas in the US they are like "prove you can make it habitable" then "can't deny". Our system is now better thanks to the advancement of solar. Sep 21 '18 at 9:51

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