Can My House Take a Heat Pump?

Before you start

Answer what you know and skip what you don't. You do not need the model number of a unit you have not bought. Without it we tell you the largest unit your service carries instead of guessing at one.

Which calculation this is. The existing dwelling method, NEC Article 220.83. It answers one question: whether the service you already have carries what you are adding. It is not a design for a new service, and it will not tell you what size to install if the answer comes back short. The result names the exact table used, which depends on the code edition in force and on whether heating is part of the job.

1. What are you adding?

Check everything that applies. The calculation measures the electrical service already on your house against everything you want to add, so it needs the whole list. Adding two things in the same year is common, and the answer is not the same as adding either one on its own.

EV charger Heat pump or mini-split Finishing or adding living space Another kitchen or kitchenette A laundry where there wasn't one

2. Your meter

Match the picture. Nothing needs opening.

Which meter base looks like yours?

This is the meter on the outside of your house, not the breaker panel inside. If you can, measure the metal box — about 15 inches tall is the standard 200 A size, and that one number tells us a lot about what your upgrade would involve.

Pick the one that looks closest. If none of them match, choose “Not sure” — a photo settles it faster than a description.

Whatever you pick here, the utility has to cut power and give us access to the meter before any work on the service can start. We arrange that with them.

Do you already know your service size?

Only if you know it for certain — from an inspection report, a previous permit, or an electrician who told you. Please don’t open the meter to check. Leave it blank if you’re not sure; the picture above is enough to get started.

3. The panel

Check anything that matches. Skip anything you're unsure of, because a wrong guess here is worse than a blank.

What's on it

Federal Pacific or Stab-Lok Zinsco or GTE-Zinsco Screw-in fuses, not breakers No single main, several breakers on top Ordinary modern breaker panel

Room inside

Several empty slots One or two empty slots Completely full

4. The house

Where is it? *

Seattle amends the electrical code separately from the rest of the state, and the EV charger figure is one of the things it changes.

Heated living area now, sq ft * Not counting an unheated garage.

Being added or finished, sq ft A finished basement or a converted garage counts. The code works from the area after the job, not before it.

There is more than one kitchen An ADU, a mother-in-law unit, a wet bar with its own circuits. Rare, but each one adds about 3,000 VA before a single appliance is plugged in.

5. Kitchen appliances

The two small-appliance circuits every kitchen has already cover whatever is plugged into them. An appliance only gets counted separately if it is built in, hardwired, or on its own breaker.

A countertop microwave on a kitchen outlet: already counted, leave it unchecked. An over-the-range or built-in one: check it. Dishwashers and disposals are almost always hardwired or dedicated. Refrigerators vary and are hard to tell from the outside, so if you are not sure, check it anyway. That is the cautious side and it will not undersize you.

6. The big ones

Gas appliances draw nothing electrically, so a house on a gas range has more room than the same house all-electric.

7. Heating and cooling now

What is in the house today, before anything you are adding. Heating and cooling never run at the same time, so only the larger of the two counts.

Current heating *

Furnace size, kW

How many, roughly? (optional) Only affects a note we show you, not the number itself, so a rough count is fine and skipping it costs nothing.

Central air conditioning, kW

8. Anything else

Sauna, pool or well pump, shop subpanel, welder, second panel. Anything fastened in place that the list above missed. Use the nameplate figure, not an estimate of what you think it draws.

Already have an EV charger?

There is already a charger on this service

Yes, there is something else

The EV charger

How many are you putting in? *

Two chargers are not the same as one charger twice over on paper. The code gives each unit its own minimum figure, so a pair of small chargers can count for more than you would expect.

Size *

Two numbers because a charger draws about 80% of its breaker for hours at a time. Go by whichever you know. If yours is not listed, pick the nearest size below it and say so when you call.

Does it manage its own load?

The heat pump

Does it have backup electric heat? *

Ductless mini-splits usually have none. A ducted system replacing a furnace usually does, and on the quote it is called "auxiliary" or "backup heat". If the quote does not say, it is worth asking, because where it exists it is normally the number that decides the answer rather than the outdoor unit.

How much backup heat? *

Can the backup heat be locked out while the compressor runs?

An outdoor thermostat or lockout relay. It changes the calculation a lot, and it is a control change rather than a service change.

Outdoor unit nameplate amps (if you have it) The outdoor unit has a data sticker on its side. Nothing needs opening. On conventional units, find the compressor line: COMPR. MOT. followed by a number and RLA. That is the one. On mini-splits and most newer inverter units there is no RLA line; find RATED CURRENT and use the largest number shown. Skip MCA, MAX FUSE, BREAKER, and LRA. Those are wire sizing, protection, and startup figures, all deliberately larger than the running load. Not installed yet? The model number on your quote plus the manufacturer's spec sheet gives the same figure, or ask your installer. Leave blank and we will tell you the largest unit your service carries.

This is a planning estimate from Hanco Electric, based on what you entered and on the code edition and local amendments for the city selected. It is not a design, not a permit submittal, and not a substitute for a licensed electrician evaluating your installation on site. The authority having jurisdiction has the final say on any load calculation.