Template: dwelling load calculation worksheet (optional method, existing-dwelling method, EV and heat pump)
In one paragraph
A one-page worksheet that produces the number the permit application asks for, by the code's own methods: the optional method of 220.82 for a new or fully known house (general loads at 100 percent of the first 10 kVA and 40 percent of the rest, plus the largest of heating or cooling), the existing-dwelling method of 220.83 for adding load to an old house, and the utility-data method of 220.87 (twelve months of maximum demand at 125 percent plus the new load). The EV line carries the 2023 edition's 7,200 volt-ampere floor. Beside the blank, the worksheet filled in for a 2,100-square-foot house adding a heat pump and a 40-amp EV circuit, run all three ways.
The rule
A dwelling's calculated load under the optional method is 100 percent of the first 10 kVA of general loads and 40 percent of the remainder, plus the largest heating or air-conditioning load at the percentages 220.82(C) gives (2025 CEC 220.82); an existing dwelling's new load may be checked by 220.83 (100 percent of the first 8 kVA, 40 percent of the remainder) or 220.87 (maximum demand over 12 months at 125 percent plus the new load); every EVSE counts at 7,200 volt-amperes or nameplate, whichever is larger (220.57); and the service conductors must have at least 83 percent of the service rating (310.12).
Why it matters
The permit desk, the inspector and the customer all want the same one page, and the contractor who hands it over before being asked is the one who gets the upgrade job and the one whose 'you don't need an upgrade' is believed. The worksheet is that page.