Circuit breaker panel capacity

The service load needs to be calculated per NEC 220-31. Add up the numbers and see what you get.

For an existing dwelling unit presently being served by an existing

volt, 3-wire service, it shall be permissible to compute load calculations as follows:

Load (kVa) Percent of Load

First 8 kVA of load at 100

Remainder of load at 40

Load calculations shall include lighting at 3 volt-amperes/ft2 (0.093 m2); 1500 volt-amperes for

each 2-wire, small-appliance branch circuit and each laundry branch circuit as specified in

Section 220-16; range or wall-mounted oven and counter-mounted cooking unit; and other

appliances that are permanently connected or fastened in place, at nameplate rating.

If air-conditioning equipment or electric space-heating equipment is to be installed, the following

formula shall be applied to determine if the existing service is of sufficient size.

Air-conditioning equipment* 100%

Central electric space heating* 100%

Less than four separately controlled space-heating units* 100%

First 8 kVA of all other loads 100%

Remainder of all other loads 40%

Other loads shall include the following:

1. 1500 volt-amperes for each 20-ampere appliance circuit

1. Lighting and portable appliances at 3 volt-amperes/ft2 (0.093 m2)

2. Household range or wall-mounted oven and counter-mounted cooking unit

1. All other appliances fastened in place, including four or more separately controlled spaceheating

units, at nameplate rating