100Amp enough for a 750sqf 2/1 unit?

[Andrew S.]

I' m planning on renovating a 2x 2/1 duplex (ca 1500 sqf total). Current electricity supply is 100Amps for each unit. My GC claims this is plenty of power since hot water and furnace both run on natural gas. I was considering upping the power supply to 150 or 200Amp for each unit on the assumption that demand for electricity will only increase over time.

Who is right? Should I leave "good enough" alone or is it worth paying now to avoid potential shortfalls in the future?

[Jon Holdman]

Actually, codes have a formula for sorting this out. The total service size isn't the total of all loads in the house. Its usually less than that.

So, add all those up, divide by 240 and you get your amp rating.

That said, you usually don't have to upgrade unless you're doing major work.

If you're doing any rehabbing, a copy of the code for your area is a very handy book.