Can a 100-Amp Panel Handle a Heat Pump?
Usually yes. A heat pump draws less than most people expect, and most 100-amp services have more room than a worst-case calculation shows. Here are the real numbers, what actually causes problems, and how to document it for a permit.
Short answer: in most homes, yes. The heat pump itself is rarely the problem. What pushes a 100-amp service over the line is usually large electric resistance backup heat, or a worst-case load calculation that overstates what the home already uses.
What a heat pump actually draws
Always use the nameplate of the equipment being installed. As a rough guide:
| Equipment | Typical circuit | Approximate load |
|---|---|---|
| Single-zone mini-split | 15–20 A, 240 V | 1–3 kW |
| Multi-zone mini-split | 25–40 A, 240 V | 3–6 kW |
| Central ducted heat pump, 2–4 ton | 25–50 A, 240 V | 4–8 kW |
| Electric resistance backup strips | 30–100 A, 240 V | 5–20 kW |
| Heat pump water heater, 240 V | 30 A | up to 4.5 kW with elements on |
Two things stand out. A heat pump replacing a central air conditioner often adds very little, because the AC it replaces drew a similar amount. And the backup heat strips can draw more than the rest of the house combined.
What a 100-amp service can deliver
100 amps at 240 volts is 24 kW. Lawrence Berkeley National Laboratory measured the annual peak of 11,940 homes and found an average of 9.7 kW, around 40 amps. The typical home leaves more than half of a 100-amp service unused at its busiest moment of the year.
Running the numbers
Under NEC 220.87, the measured peak is taken at 125 percent and the new load is added:
| Heat pump only | Heat pump + 10 kW strips | |
|---|---|---|
| Measured peak, 9.7 kW at 125% | 50 A | 50 A |
| 3-ton heat pump | 30 A | 30 A |
| Backup strips | — | 42 A |
| Total | 80 A, fits | 122 A, does not fit |
Same house, same heat pump. The strips decide the outcome.
Why the traditional calculation often says no
Under the 2020 and 2023 editions, the 220.83 method counts every appliance at nameplate and takes new heating equipment at 100 percent on top. (The 2026 edition takes a new heat pump at 50 percent, which helps.) In a home with an electric range, dryer and water heater, that commonly lands just over 100 amps even though the main breaker has never come close to tripping. That is a calculated overload, not an observed one, and it is where a measured calculation changes the answer.
If it is close
- Size backup heat honestly. A cold-climate heat pump in a reasonably tight home may need small strips or none. Ask for a proper heating load calculation rather than a default 15 or 20 kW kit.
- Stage or lock out the strips so they cannot run alongside other big loads, where the equipment and your AHJ allow it.
- Choose a 120-volt heat pump water heater if water heating is part of the project.
- Use a load-management device on a flexible load such as an EV charger.
- Remember what is coming out. Removing an old AC, electric furnace or resistance water heater frees capacity.
For contractors: documenting it for the permit
Inspectors increasingly want a formal calculation before approving a heat pump on an existing service. With twelve months of utility interval data, the 220.87 calculation takes minutes and does not require a site visit to inventory appliances. What inspectors want to see in a 220.87 report covers the submission itself.
Want a quick check first? Try the panel capacity calculator.
Figures here are typical values for illustration. Use the nameplate data for the actual equipment, and the code edition adopted in your jurisdiction. The AHJ has the final say.
Homeowner? Send this to your contractor
TrueLoad is used by the licensed electrician or installer who prepares the calculation. Forward them this page and ask them to check your measured demand before anyone quotes a panel upgrade.