Electrical – What size electric service do I need

electrical

My son and I are building a house at the beach. I currently have a 100 amp temp service and my question is “can I get everything I need on the service to pass code if I keep it at 100 or 125Amps”?

The inspector is telling me that I can only use 80% or 80 amps if I keep the box at 100 amps but that doesn’t seem right because the load center that I bought has a 100 amp main breakers and 145amps worth of branch breakers that came with it when I bought it new.

I have been reading the NEC codes and the way I understand it I need 2ea 20 Amp 120 circuit plus 1ea 50 Amp 240 circuit for the kitchen, 30 Amps 240 for heating and I have an AC unit that runs off of 20 Amps 240. Which adds up to 110 Amps before I do an outlet or light circuit so I must be figuring this wrong.

Should I be figuring by watts or volts instead?

Best Answer

My advice would be to install the largest service that you can get regardless of how much you plan on using in the short term. 200amps is pretty typical for a lot of residential areas in North America. Reasons:

  1. In most residential areas, you pay for what you use, not overall capacity
  2. There might not be capacity on the transformer later when you need it
  3. Replacing the feeder cables can be very expensive
  4. Replacing the meter and panel later is expensive
  5. You won't have to worry about it again

Years ago, a lot of houses only had 60amp service. Consumption increased for a while especially with the increase in electronics and lighting, but now with LED, it looks like it might be going the other way again.

Also consider what amenities you might add later. A pool, hot tub and second kitchen can easily put you over capacity if only have a small service.

Related Topic