not a real electrician, just a lowly part time contractor and am quoting a basement finishing job. the home is about 2400 sq ft with central air and is about 10 years old, it has a 100 amp panel with a few double throw breakers already added for previous work where there wasn't any more room for aditional single breakers, now i will hire an electrician to pull permits and do this right, but for quoting purposes is it required to upgrade to a 200 amp service panel or is accepable to add a small 4 circuit sub panel, i don't think that will pass figuring 2400*3\120=60 + the central air is over 100 amps, is that rule a guidline or a requirement? the owners would much rather save 6 or 700 dollars and just add a sub panel?