Do Electrical Plans include load calculations?

Yes — a formal NEC/CEC Article 220 load calculation is included in every one of our ADU Electrical Plan sets, at no additional charge. It is the engineering backbone of the set: panel amperage, the decision about whether your main service needs an upgrade, and your utility load letter all derive from it. California building departments require it as a submittal, and leaving it out is the single most common cause of electrical plan-check corrections.

What the calculation totals

The Article 220 calculation adds up every category of demand in the unit:

• General lighting and general-use receptacles: 3 VA per square foot of living area.
• Small-appliance circuits: 1,500 VA each, minimum two for the kitchen.
• Laundry circuit: 1,500 VA.
• Fixed appliances at nameplate rating: electric range/cooktop, water heater, dishwasher, disposal, microwave, and similar.
• HVAC: heat pump or air-conditioning load at rated amperage (generally the larger of heating vs. cooling).
• EV charger: included at full rated load — typically 40–50A for a Level 2 charger.

Demand factors — why the panel can be smaller than the sum

If you simply added every load at full value, panels would be wildly oversized, because no household runs everything at once. Article 220 applies demand factors — code-specified percentages reflecting that loads don't all peak simultaneously. The chosen method (standard or optional) also affects the result. The final figure, in VA, is divided by the service voltage to yield the minimum amperage, which sets the panel size.

How the load calc connects to the rest of the set

1. It justifies the panel schedule amperage and main breaker size.
2. It feeds the single-line/riser diagram feeder and conductor sizing.
3. It supports the utility load letter when you request a meter or service change.
4. It documents whether the existing main service can carry the house plus the ADU, or whether a panel upgrade is required.

Because the method involves specific code tables and judgment about which loads dominate, the calculation must be performed by a licensed electrician or MEP engineer — not estimated from square footage.

For an all-electric 700 SF ADU with induction cooking, a heat pump water heater, mini-split HVAC, and a Level 2 charger, the calculated demand commonly lands in the range that justifies a 125A subpanel — but only the actual nameplate ratings and chosen method confirm it for your project.

Why you can't skip it or copy one

Owners sometimes ask whether a neighbor's calc or a generic template will do — it won't. The Article 220 result depends on your exact square footage, your specific appliance nameplate ratings, your HVAC equipment, and your existing main-service loads, so it has to be run for your project. A missing or unsupported load calc is the most common reason an otherwise complete electrical submittal gets kicked back, which adds a correction cycle and weeks to your timeline. Including a clean, defensible calc up front is the least expensive insurance against that delay — and it doubles as the load letter your utility will ask for. Requirements vary by jurisdiction — confirm with your local building department. See the ADU electrical guide for a fuller walkthrough, or order a set from $995.