Question 1

How is residential service load calculated?

Accepted Answer

Per NEC 220.83 standard method: 3 VA/sq ft general lighting, 1500 VA per small-appliance circuit, 1500 VA laundry circuit, then apply demand factors per 220.42. NEC 220.82 optional method uses simpler percentages.

Question 2

What is a demand factor?

Accepted Answer

A demand factor is a percentage applied to a calculated load to reflect realistic usage. For example, residential general lighting demand factor is 100% for the first 3000 VA and 35% for the next 117,000 VA.

Question 3

Do I need to size service for 100% of connected load?

Accepted Answer

No. NEC Article 220 provides demand factors and load diversity allowances. Sizing for 100% of every connected load would result in dramatically oversized service equipment.

Panel Load Calc

Service Information