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enter image description hereWould a 50 amp breaker for a sub panel be enough to power up a tiny house with these features?

  • 7 can lights
  • 120v water heater
  • 5 outlets
  • bathroom GFCI
  • exhaust fan
  • Mini-split heat exchanger
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  • 2
    Why stop at 50A? 90A wire is cheaper than 50A wire because when wire gets big enough, aluminum is proven safe. So go straight to 2-2-2-4 Al. Now what are you doing for a food preparation area?
    – Harper - Reinstate Monica
    Commented Oct 2, 2023 at 19:27
  • Because the main panel is full and the only way to make room is with a quad 30 & 50 amp Bryant breaker. At least that’s the only solution I see. And it won’t have a food preparation area. It’s more like a tiny guest room separated from the house. It will only have the bedroom and the bathroom.
    – Mynor Hernandez
    Commented Oct 2, 2023 at 19:33
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    Welcome. Please take the tour so you know how to use this site.
    – isherwood
    Commented Oct 2, 2023 at 19:37
  • That hurts. Unfortunately #2 won't fit on 50A breakers, especially not tandems. You could evaluate #6AL which is actually good to 50A due to better insulation than UF cable gets. It sounds like your energy needs will be defined by the worst case of a) the mini-split, and b) the solar you put on it.
    – Harper - Reinstate Monica
    Commented Oct 2, 2023 at 19:40
  • Sorry the app just edited my question I’m not doing anything with solar.. But yeah the main question it’s just if a 50 amp breaker for a sub panel is enough to power up the tiny guest room with the features I listed.
    – Mynor Hernandez
    Commented Oct 2, 2023 at 19:48

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TL;DR Yes, but...

Keeping in mind that 50A is 50A @ 240V, which is 100A @ 120V, and most of your loads are 120V, that should be plenty:

  • 20A 120V bathroom
  • 20A 120V water heater
  • 20A 240V mini-split (there are a lot of options, you might not need this much power, depending on house size and HVAC efficiency)
  • 20A lights/convenience receptacles

However, the formal way to do this is a Load Calculation. And there is one key piece that you are missing to turn a tiny house into a functional "home": cooking appliances. Electric cooktop, oven, microwave oven - anything will use a good bit of power when running. So that's the key missing link to see if 50A is really enough. Comments indicate no real cooking appliances, so this is probably OK.

As Harper already noted in a comment, once you get past 30A, switch to aluminum wire, and with aluminum wire there is usually good price on 2/2/2/4 cable that is good for up to 90A. But be careful: before jumping to "OK, I'll put in 90A and have more than enough for anything" (well, except tankless hot water or unrestricted EV charging), you have to do a Load Calculation at your main panel/utility service to determine how much power you can spare for the tiny house. If you have 200A service and not too much stuff, 50A or 60A or maybe even 90A will be fine. If you have 100A service, or if you have a lot of big electric appliances in the main house then you may have a problem.

Comments indicate the existing panel is FULL. That doesn't necessarily mean anything, but consider the checking account analogy: If you run out of checks (breakers), you haven't necessarily run out of money, but if those checks you wrote were for large amounts then maybe you did run out of money. So a formal Load Calculation of the main panel is important. In addition, a picture of the panel might help identify some potential safety and/or usability issues.

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    Thank you!! But yeah it’s going to be more like a guest bedroom away from the house so it won’t have a kitchen it will only be the bedroom and the bathroom. So 50amps should be enough right?
    – Mynor Hernandez
    Commented Oct 2, 2023 at 19:36
  • Based on the loads you listed, 50A is even overkill. The load calculation is to see if you can add these loads to the panel at the main house. Also: what's the solar panel have to do with anything? It sounds like you're just doing conventional wiring.
    – KMJ
    Commented Oct 2, 2023 at 19:42
  • Yeah the app just edited my question I’m not doing anything with solar. Sorry. But yeah the main question it’s just if a 50 amp breaker for a sub panel is enough to power up the tiny guest room with the features I listed.
    – Mynor Hernandez
    Commented Oct 2, 2023 at 19:47
  • And if it is do you have a sun panel brand that you would recommend? The main panel in the house has Bryant breakers
    – Mynor Hernandez
    Commented Oct 2, 2023 at 19:50
  • It doesn't really matter much which brand - any UL listed brand should be fine. The main ones are GE, Square D (low end Homeline, high end QO), Eaton (low end BR, high end CH), Siemens. But don't get a "sub" panel. Get a "main" panel. Why? Because they really don't cost much more, the workspace requirement is the same for any panel, and you get an included "main breaker" (much bigger than your feed breaker, but that doesn't matter at all) which functions as your required Disconnect switch. Your minimum here would be a 12-space subpanel, but a 20 space "main" would be much better (and larger is
    – manassehkatz-Moving 2 Codidact
    Commented Oct 2, 2023 at 19:58

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