What a heat pump actually draws
A typical 3-ton residential heat pump draws roughly 15-25 amps at 240V during normal cooling or heating operation — comparable to a straight AC of the same tonnage. The additional load comes from two places: electric auxiliary heat strips (used as backup below the system's efficient operating temperature) and the inrush current at compressor start.
Auxiliary heat strips are typically sized at 5-15 kilowatts for residential heat pumps. A 10 kW strip at 240V draws roughly 42 amps when energized. The strips don't run continuously — they're a backup, not primary heat — but the panel has to be able to supply them when they do run.
What a panel load calculation evaluates
A standard NEC-based residential load calculation sums up:
- General lighting and small-appliance loads (per square foot, per code factors)
- Fixed appliance loads — water heater, dryer, range, etc.
- HVAC — current and planned equipment
- Electric vehicle charging if present or planned
- Any other 240V dedicated loads
When a panel upgrade is actually required
On a 200-amp panel with modest existing loads (gas water heater, gas dryer, gas range, no EV charging), a residential heat pump plus moderate aux heat typically fits comfortably — no upgrade needed. On a 100-amp panel with the same modest loads, the heat pump plus aux may or may not fit; the load calc tells you.
The upgrade becomes genuinely necessary when: the panel is 100A and the home already has significant electric loads (electric water heater, electric range, EV charging), the panel is 100A and the heat pump plan includes large aux heat strips, or the panel is older than the 1990s and lacks space for the required new breakers regardless of amp rating.
The dual-fuel escape hatch
A dual-fuel (hybrid) configuration — heat pump plus existing gas furnace as backup — eliminates most of the auxiliary-heat panel load. The gas furnace handles cold-weather backup instead of electric strips, so the heat pump install adds roughly the same panel load as an AC changeout would.
For homes where panel capacity is tight and a service upgrade isn't practical, dual-fuel is often the right design — you get the operating-cost benefits of a heat pump without the panel-size constraint of a fully-electric setup.
What the panel upgrade actually looks like
When a service upgrade is required, the scope is: new service entrance cable from the utility drop or meter, new main panel at higher amperage (typically 200A), reconnection of all existing circuits to the new panel, and a utility coordination for the service disconnect-reconnect. The permit is pulled with the electrical department; the utility schedules the final cutover.
A 100A to 200A upgrade is a few-thousand-dollar project in most Sacramento-region jurisdictions and typically completes in one day plus utility coordination. It's not a trivial add, but it's not a show-stopper either — and it unlocks electric vehicle charging, kitchen electrification, and other future-proofing beyond the heat pump itself.
Common questions
How do I know if my current panel has 100A or 200A service?
The main breaker in the panel is labeled with its amperage — 100A, 125A, 150A, 200A. If you can read the breaker label, you have your answer. The service entrance cable size also indicates service capacity but requires an electrician to confirm.
Can I just skip the auxiliary heat strips and save the load?
On a cold-climate-rated heat pump properly sized for the heating load at design temperature, you can — the heat pump handles the full winter without strip backup. On a mild-climate or budget heat pump, strips are necessary insurance. The decision is tied to equipment choice and your tolerance for a rare cold-snap performance gap.
Does my utility have a program that pays for panel upgrades?
Programs change over time; PG&E, SMUD, and the Roseville/Lincoln municipal utilities have various rebate and incentive programs that sometimes include panel-upgrade components. The current state of these programs is visible on the utility's website; we don't quote amounts here because they'd be out of date quickly.
What's the right size panel for electrification?
200A covers most residential full-electrification scenarios (heat pump + heat-pump water heater + induction range + dryer + EV charging). 400A is appropriate for larger homes with multiple HVAC zones or heavy EV loads. Below 200A, careful load management is required if the home is going full-electric.