200 amp services all electric houses

**Greg1707** · 05-03-17, 05:38 PM

This week we replaced panels in two houses built in the 1970s. Both are all electric. One was a 1,100 square foot town house and the other was a 2800 square foot ranch house with basement. No pools or anything extra.

Both houses had 200 amp services.

Maybe one house was oversized and the other was undersized?

**peter d** · 05-03-17, 05:46 PM

200 amps goes a long way, much further than most people are accustomed to thinking. Of course, the real answer depends on a load calculation, but keep in mind that the NEC is highly conservative and the actual load, even with electric heat, will be well under NEC calculations.

**jaggedben** · 05-03-17, 06:34 PM

The difference in load calculation for that 1700 sq ft difference is 5100VA or only 21.25amps on a 240V service. So since you're most likely going to 200A if you need more than 125A, that 21A really doesn't mean much. The appliances matter to the load calculation a whole lot more than the square footage. Not to mention these days with fluorescent and LED lighting the 3VA per sq ft calc is probably a few times what's really needed.

I've done a bunch of load calculations for existing dwellings (220.83) and very few have needed more than 100A. I did one that had two ovens, a dryer and a car charger, and it came to 99A.

**Fnewman** · 05-03-17, 08:03 PM

Around here it is rare to see anything but 200A in most houses up to sf limits set by various AHJ (varies some). Then it is 400A.

**peter d** · 05-03-17, 09:46 PM

In my area, a smaller new house with all gas appliances and high efficiency central a/c will almost always have a 100 amp service.

**JFletcher** · 05-04-17, 12:32 AM

Originally Posted by jaggedben

The difference in load calculation for that 1700 sq ft difference is 5100VA or only 21.25amps on a 240V service.

This.

In this area, it's fairly unusual to see 100A services; most are 125+A... even this house has a 125A FPE panel ca 1953 in it. Most everything is electric here tho; gas wasnt widely available until the late 80s, so electric baseboard heat, electric dryer, oven, stove, dryer, water heater, and HVAC. Add in well pump, garbage disposal, toaster, microwave, coffee pot (SABCs), washing machine, etc etc and its quite possible to 'need' a 200A service. Practically tho, we do full house generators in the 18-24kW range, so you'd really have to try to exceed 75A unless there are 2+ HVAC units, spa, and so on.

Like Peter D mentioned, new homes with gas appliances can easily get by with 100A services.

eta: Greg, were they aluminum wire, or late 70s with copper?

**Greg1707** · 05-04-17, 08:24 AM

ALUM. Including the GEC to water pipe.

Originally Posted by JFletcher

This.

In this area, it's fairly unusual to see 100A services; most are 125+A... even this house has a 125A FPE panel ca 1953 in it. Most everything is electric here tho; gas wasnt widely available until the late 80s, so electric baseboard heat, electric dryer, oven, stove, dryer, water heater, and HVAC. Add in well pump, garbage disposal, toaster, microwave, coffee pot (SABCs), washing machine, etc etc and its quite possible to 'need' a 200A service. Practically tho, we do full house generators in the 18-24kW range, so you'd really have to try to exceed 75A unless there are 2+ HVAC units, spa, and so on.

Like Peter D mentioned, new homes with gas appliances can easily get by with 100A services.

eta: Greg, were they aluminum wire, or late 70s with copper?

**Dennis Alwon** · 05-04-17, 08:59 AM

I agree the difference is sq.ft is not that significant and given that a 200 amp panel is probably cheaper than 150 amp panel I believe that is why there are 200 amp services at both houses. All electric house is automatically a 200 around here and depending on size and number of heat pumps it can easily be 400 amps.

**kwired** · 05-04-17, 09:50 AM

Originally Posted by Greg1707

This week we replaced panels in two houses built in the 1970s. Both are all electric. One was a 1,100 square foot town house and the other was a 2800 square foot ranch house with basement. No pools or anything extra.

Both houses had 200 amp services.

Maybe one house was oversized and the other was undersized?

My house is closer to fitting your 2800 square foot one and is also all electric. I have a 200 amp service to it, but would guess if I put in a 100 amp main it may trip on rare occasions, make it a 125 amp main and it probably would never trip. POCO only has a 25 kVA transformer supplying not only the house but some other outbuildings, they don't expect to see high load for any long period of time either.