Heat pump electrical panel requirements come down to three things: a dedicated 240-volt circuit sized to the outdoor unit’s nameplate, a disconnect within sight of the unit, and enough service capacity for the heat pump, any electric backup heat and everything else the house already runs. Most houses meet the first two easily. The third is where panel upgrades come from.
The Seattle Heat Pump Company plans ducted heat pump projects across Seattle and King County, including the electrical scope, and the work is carried out by licensed and insured contractors. This guide explains what an electrician checks, why electric backup heat changes the answer more than the heat pump does, and what a 100 to 200 amp upgrade involves when it is needed.
Key takeaways
- Every heat pump needs a dedicated circuit and an outdoor disconnect. That part rarely forces an upgrade.
- Electric resistance backup strips can draw several times the current of the heat pump itself.
- A 100 to 200 amp upgrade typically runs about $1,333 to $4,500 in the Seattle area, before utility-side work.
- Seattle's electrical permit is currently $110.38 for a circuit and $410.84 with a 200 amp service.
The circuit and the disconnect
The outdoor unit’s nameplate lists two numbers that set its circuit. Minimum circuit ampacity tells the electrician how heavy the wire must be. Maximum overcurrent protection sets the largest breaker allowed. A variable-speed ducted heat pump commonly lands on a two-pole breaker in the range a large appliance would use, though the exact figure is model-specific and comes from the nameplate, not from a rule of thumb.
The electrical code also requires a disconnecting means within sight of the outdoor unit, usually a small weatherproof box on the wall beside it. It lets a technician cut power at the unit while working on it, rather than trusting a breaker in a basement panel two floors away. A short length of liquid-tight conduit, often called a whip, runs from the disconnect to the unit.
The indoor side needs power too. A heat pump coil on an existing gas furnace uses the furnace’s existing 120-volt circuit for the blower and controls. An electric air handler is different: it needs its own circuit for the blower, and a much larger one if it contains resistance heat strips. That distinction is often the first sign of whether a project will stay small electrically. The air handler replacement page covers the indoor choice in more detail.
Why backup heat matters more than the heat pump
A heat pump moves heat rather than making it, so it draws relatively little current for the heat it delivers. Electric resistance heat makes heat directly from electricity, one unit of heat per unit of electricity, which means it draws a lot of current for the heat it delivers.
The arithmetic is plain. Current equals power divided by voltage. A 10 kilowatt heat strip on a 240-volt circuit draws about 42 amps by itself, and 15 kilowatts draws about 63 amps. Those strips sit in the air handler and can run at the same time as the outdoor unit on a cold morning. On a 100 amp service that already carries an electric range, a dryer and a water heater, that load can be more than the service can carry.
There are several ways to handle it, and the right one depends on the house:
- Size the strips to the real need. A Manual J calculation shows how much heat the house needs below the heat pump’s balance point. In Seattle’s climate that is often far less than the largest strip kit the air handler accepts. The sizing guide explains the balance point.
- Stage the strips. Controls can bring backup heat on in steps rather than all at once, and Seattle’s energy code already keeps it off above 40°F, with the lockout set to 35°F or lower at final inspection.
- Keep gas as backup. A dual fuel heat pump puts the heat pump coil on a gas furnace, which supplies the backup heat with no resistance strips at all. That can avoid an upgrade entirely.
- Use load management. Some designs add a device that prevents two large loads from running at once, where the electrical code and the local inspector accept it.
How the strips are controlled after installation matters as much as their size. The backup heat settings guide covers lockouts and thermostat staging.
The service load calculation
Whether a panel is big enough is not a judgment call. The electrical code includes a method for calculating a dwelling’s service load: it counts general lighting and receptacle load by floor area, adds the fixed appliances, applies the demand factors the code allows, and then adds heating or cooling, whichever is larger. The result is compared with the rating of the service.
An electrician can do that calculation from the panel schedule and a walk through the house. Some also look at the utility’s record of the home’s actual peak demand, where it is available, as a check. Either way, the calculation, not the number printed on the main breaker, tells you whether the heat pump fits.
Panel capacity is a separate question from service capacity. A panel can have enough amps but no free spaces for a new two-pole breaker. That can sometimes be solved with a subpanel or by consolidating circuits, without touching the service.
When a 100 to 200 amp upgrade makes sense
A panel upgrade for a heat pump is warranted when the load calculation says the existing service cannot carry the heat pump, its backup heat and the rest of the house, and the cheaper fixes above do not close the gap. It is also worth considering when other electrification is planned soon, such as an induction range, a heat pump water heater or a car charger, because doing the service once costs less than doing it twice. Electric backup heat also shows up on the bill, which the operating cost guide works through.
The work typically involves a new panel, new service entrance conductors and often a new meter base, along with coordination with the utility to disconnect and reconnect the service. In the Seattle area, a 100 to 200 amp panel upgrade typically runs about $1,333 to $4,500 a budgeting range rather than a quote. National figures put it at $1,800 to $4,500 (Fixr). Those figures cover the panel side. City Light does not publish its own service-side charges for an upgrade, so ask about utility work when the service drop or meter location has to change.
Homeowners regularly report electrical lines on competing heat pump quotes that differ by a factor of two for the same house. Most of that gap is scope. One bid includes a service upgrade with new conductors and utility coordination; another includes a circuit and assumes the existing service is fine; a third sized large backup strips that make the upgrade unavoidable. The quote comparison guide shows how to line those up.
Find out whether your panel can carry a heat pumpThe assessment checks the service, the panel and the backup heat plan before equipment is chosen.
Get an EstimateElectrical permits by city
Electrical work for a heat pump needs a permit, and who issues it depends on where you live.
| Location | Electrical permit office | Notes |
|---|---|---|
| Seattle | SDCI | Current fee $110.38 for a circuit; $410.84 with a 200 amp service, both including the 5% technology fee |
| Bellevue | City of Bellevue | Electrical permit for wiring or service work, alongside the mechanical permit for the heat pump |
| Kirkland, Redmond, Renton, Burien, Mercer Island | The city | Each issues and inspects its own electrical permits |
| Shoreline, Lake Forest Park | Washington Labor & Industries | The state issues and inspects electrical work in these cities |
In Seattle, the electrical permit sits beside the refrigeration permit that every split heat pump needs, and a furnace or mechanical permit when the indoor equipment changes. A typical job’s permits run about $192 to $556 under SDCI’s current fee schedule. The Seattle permit guide lists each one and who pulls it.
What to check before you sign
A sound electrical scope on a heat pump quote states:
- the circuit size and breaker for the outdoor unit, from the nameplate
- the disconnect location
- whether the air handler gets a new circuit, and the backup strip size in kilowatts
- the result of the service load calculation
- whether a panel or service upgrade is included, and what utility coordination it covers
- the electrical permit and who pulls it
The installation cost guide shows how the electrical scope fits into the total, and the cost estimator lets you test a budget with and without a panel upgrade. For the electrical check on your own house, it is part of every ducted heat pump installation assessment, and the installation process guide shows where the electrical work falls in the sequence.