Does a panel upgrade for a whole-house remodel need a load calculation?

Usually, yes. Building departments commonly require an electrical load calculation with a service or panel upgrade permit, and the utility evaluates new load before it changes your service. Foster City's 2025-code handout, for example, lists a residential electrical load calculation form and a PG&E approved plan among the items required to get a main service panel upgrade permit.

Which calculation method

Article 220 of the California Electrical Code offers several methods. A guide for building officials from Silicon Valley Clean Energy summarizes them:

• 220.82. The standard optional calculation for dwellings, most often used for new construction.
• 220.83. A method for existing dwellings adding new loads, with different factors depending on whether air conditioning or electric space heating is being added.
• 220.87. Uses the home's actual measured peak demand from utility meter data: one year of data, or 15-minute data for at least 30 days if a year is not available, with 125 percent of the maximum demand used in the calculation.

Danville's dwelling load calculation form, for example, is based on the 220.83 method and treats additional loads to existing dwellings differently from new dwelling units. Ask your department which methods it accepts.

What departments and utilities ask for

• Foster City. A permit application, the PG&E approved plan for new service upgrades, the load calculation form and an upgrade worksheet. Its handout also covers working clearances of 36 inches deep, 30 inches wide and 6 feet 6 inches high under CEC 110.26, and circuit identification.
• Santa Clarita. A 2018 handout says service upgrade permits are issued to licensed C-10 electrical contractors, and that upgrades of 400 amps or more need professionally prepared plans, a load calculation, a single-line diagram and panel schedules.
• PG&E. Its panel upgrade roadmap says any new load addition requires an evaluation and an application through PG&E, that the load assessment can take up to 30 days, and that power is reconnected after the panel is replaced and the city inspector approves.

Why the calculation matters for a remodel

• A whole-house remodel often adds a heat pump, a heat pump water heater, an induction range or an EV charger at the same time.
• The calculation shows whether the existing service can carry the new loads or whether an upgrade is needed.
• Choosing lower-demand equipment, or using the 220.87 method with real meter data, can change the answer, so run the numbers before committing to an upgrade.

What this means for your MEP plans

The electrical sheets should include the load calculation, the panel schedule and, for larger services, a single-line diagram, all matching the equipment on the mechanical and plumbing sheets. MEP Plans USA prepares residential electrical plans with load calculations for California projects. See electrical plans and electrical load calculations. Utility and city requirements vary, so confirm with your building department and utility.

Sources: fostercity.org, danville.ca.gov, santaclarita.gov, pge.com, svcleanenergy.org.