Two Electrical Panels / Systems for One House
Hoping for some good input on this concept: Two separate electrical panels for separate wired areas, solar and traditional.
I am ready to build an energy efficient home and live in Kansas which requires home owner to be hooked up to the grid.
My question is can we have a portion of the house wired for a solar application and the other part of the house wired to a traditional electrical panel.
Yes two completely separate wiring. As if two houses under one roof.
We want one panel solar which would have backup. And the other to be another 200amp traditional wired to the electrical grid.
We are not allowed to net meter as Free State has moved to Parallel metering.
I would like two separate 200amp panels to run completely separate wired parts of the house depending upon how we initially have it wired. We feel that we have certain parts of the house that should be allowed to be up and running despite the electrical company wanting limit or turn off everyone’s electrical service as needed in case of emergencies. I understand that power feed back would be dangerous, and we wouldn’t want to endanger power employees. So why not keep use separate with different wiring.
And on the other hand, I do not want a power company dictate to me when my power is shut off to me, nor dictate my limits.
Hence, I propose to completely have the important systems to be wired to a solar collection/storage panel and tamped to a 200amp service and a second 200amp panel that runs part of house that isn’t as critical to us that is hooked to community electrical provider.
That way they can still charge us the fees they dictate and turn us off/ on at their discretion, but only a portion of the house.
I think this would be a win/win for both parties.
So Green Building community, do you think this is feasible and how do I go about implementing this plan?
~DA Rush
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Replies
The typical approach is a meter disconnect and a transfer switch. The wiring is the same, you just flip a switch to go from grid power to PV (or generator) power.
I do not think it would be legal for any branch of the government to require a grid connection.
Maybe you bought into an HOA with deed convents that require the grid connection.
You could put a transfer switch ahead of the panel disconnecting the grid from all your loads and allowing the solar to power them. This would be code compliant all or nothing choice.
You could have 2 separate system two light switches by each door one would turn on a light fixture power by the grid and the other switch would turn on a second fixture power by solar. But you would need 2 heat pumps 2 water heaters etc. two of everything you that does not come from the manufacture with a plug and cord. This would be code compliant anything you want choice.
What the code will not allow more than one breaker powering the same load. It would be too easy for a repairman to get confused and injured.
My guess is after you see the price tag for a battery large enough power your home for the 3 coldest days you will decide that you can live with ever the grid will give you.
Walta
You could do what you described, the solar system and all downstream wiring would be what is known as a "seperately derived system", which has specific meaning in the code, and specific rules you have to follow. It is imperitive that the two systems share a common ground point, which is easy: you use the same ground system (a few ground rods, a city cold water pipe, etc.) to ground everything. The panel for the solar system would have a ground-neutral bond, as would the utility-side panel. There could be NO downstream connections between the two systems, period. This would accomplish what you describe, would meet code, but would mean loads supplied from the solar system would ONLY be able to draw power from the solar system. If the solar system is not producing, and your battery system was depleted, you would have NO way to supply those loads from the utility-side panel.
I would not recommend such a system for a variety of reasons. The big reason is that the solar system is very unlikely to be able to supply a large amount of your home's loads for any appreciable length of time, especially in the winter. Battery systems have maintenance requirements, carry risks, and are very expensive for any significant amount of capacity in terms of stored kWh. I generally advise against solar "backup" power systems like this, especially systems intended to support the load levels required for what you'd probably consider your "critical" loads (HVAC, refrigeration, some lights, etc.).
Most solar systems can only operate when tied to the grid. This is because the synchronize with the grid, and are what are known as "grid following" inverters. These systems synchronize themselves with the utility's power waveform, then adjust their operation to deliver power in parallel with the utility. These type of systems are designed to drop out (disconnect) and shut down when there is no grid power present to sync to, which prevents the backfeed situation you mention. Solar systems that can supply loads indepently from a grid connection are what are known as "grid forming" inverters, and they can run on their own, in what is known as an "islanded" configuration. Most residential solar inverters are not of the grid-forming type.
You don't need net metering to use solar. You can use a grid tied system in what I call "peak shave" mode, which means it won't back feed into the grid, but will just provide however much power your home is using at any given time, up to the capacity limits of the solar system and the amount of solar energy available for it to make electricity with. These sytems tend to be much cheaper to install compared to battery systems, they are more reliable, they require very little maintenance, and you don't need to worry about net metering or billing issues. You just need to make sure there is no prohibition against connecting such a system. Remember that "net metering" is entirely a BILLING system, it has nothing to do (not really, anyway) with connecting a solar system to your home.
If you want to do a sort of hybrid system, what I would do is use an automatic transfer switch (an ATS), and use that to switch a subpanel that powers your critical loads over to the solar system if the utility fails. This would make your solar system "look" like a backup generator to teh ATS, and would let you set things up for backup power in a simple way using readily available equipment and avoiding any code issues with a non-standard installation.
Note that utilities are typically required by statute to provide power to everyone, all the time, except under certain emergency situations. They are not in the buisness of turning people off for fun or no reason. Remember that they make no money when they aren't selling you power. They have no incentive to "turn you off". The only times you are likely to see an intentional shutoff from a power provided is in the case of certain types of system maintenance that can't be safely performed while things are live (and you usually get advanced notice of this sort of work), and during system stability emergencies (which is what happened in Texas a few winters ago), where the grid can't support the load due to a lack of sufficient generation. In those situations, which are extremely rare, the choice for the utility is "turn off a little RIGHT NOW for a little while" or "lose everything IN A MOMENT for A LONG TIME". They don't like being in that situation, but they have to act to protect the system in those cases.
Bill
If you want a 200 amp panel, no solar back feed, and a pretty much "Off grid" setup while using grid only as a supplement, a Sol-ark 15k might get what you need. EG4 also has their 18k that is very comparable. Both these inverters are hybrid, you can set them to do zero back feed. And they have 200 amp pass through, so solar powers everything, and it is just supplemented with the grid. They are both a bit pricey, but the simplicity of wiring may pay for itself. When the grid is turned off, the Solark can power most of your house still (as long as your batteries are big enough).
Setup would basically be:
Meter -> Inverter -> 200 Amp Main panel
You don't need two completely separate electrical systems in order to have power during an outage. You're drastically overthinking things.
You need a hybrid inverter and some battery storage.
Take a look at your fixed meter charges. Here it is about $33/month, even if you use zero power. Long term, you may not like that extra expense with a 2nd meter if trying to mitigate cost.