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Our house is mid 1990's with 200 Amp service. The meter is on a garage wall (attached to the house) and the panel is in the laundry room about 20 meters / 60' distant. I'm not sure how the panel feed runs from the meter, but think it may be under the garage slab, entering the house via the crawl space. The panel is 100% used, although many circuits serve only one or at best a few outlets.

The issue I have is that the original owner only put 1 15 amp service to the garage.

I am a wood worker and plan to buy an electric vehicle in the next year or so, so want more circuits to the garage - 120 and 240V, but as the main is full and the garage is on slab, this is not a simple proposition.

What I would like to do is add a new panel in the garage, on the inside wall directly behind where the meter is located. My thinking is to make it the main panel, with the existing panel converted to being a sub panel.

In the new garage panel, there will be a need for 60-100 Amps to feed the new ccts for power tools and a vehicle charger. The rest of the power in the house will be unaffected.

The major power users currently on the main panel are a heat pump and electric hot water heater. The heat pump (60A) can be moved to the garage panel fairly easily, the hot water tank cannot.

My question, before bringing in electricians to quote on the job, is whether / how I can achieve my goal. Is it feasible to convert the existing main to a sub panel & bring all power from the meter to the new garage panel and then feed the existing panel from it or is there something else I need to consider?

Suggestions welcomed

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    Can you upload a picture of the existing main panel and of the meter (which may have additional boxes/cutoff switches/breakers/etc. near it which may or may not be relevant)? Feb 14, 2021 at 3:28
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    There might be an option with upgrading the meter to a "class 320" (320A continuous rated, or 400A "normal") and feeding two 200 A panels (the existing and a new one in the garage) from that, but it may depend on your power utility's rules, so what your power utility is might also be useful information.
    – Ecnerwal
    Feb 14, 2021 at 3:32
  • The other factor is how close you are to 200A right now, in terms of real-world usage. If you have gas heat and stove and hot water that is very different from electric everything, especially if you have on-demand electric hot water (a lot of questions about that lately). A lot of that can be determined from looking at your panel. Feb 14, 2021 at 3:43
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    Can you post photos of the existing panel please? Also, how many square feet is the house, and can you post photos of the nameplates on the heat pump indoor and outdoor units please? Feb 14, 2021 at 3:48
  • 2 ideas: 1) Like ecnerwal suggested, it might be more feasible to upgrade to a class 320 service (you'd need to involve the power company) or 2) Make your new panel a sub-panel, fed from the main panel. You said you could easily move the heat pump breaker to the new panel, that would give you space for a breaker to feed the sub-panel. If you go that route, get a big sub-panel and feed it with a 125 am breaker. With your planned changes, you should also do some total load calculations to determine the best route. Feb 14, 2021 at 15:19

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This is a feasible undertaking. You should be able to reuse the existing run from the meter and land it at the new main panel. You can also have the electrician pre-run the wires for the car charger

For the new main panel, install a panel with more spaces that you think you'll need, you already saw the result of not having enough spaces.

The biggest thing to make sure is that the current panel has it's neutral and ground completely separated when it becomes a subpanel. Many times in the main panel the grounds and neutrals will be on the same bar, but in a subpanel they must be completely isolated from each other. How easy this conversion is depends on how much slack the previous installer left on each wire.

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