What size electrical service does my house need?

It depends on floor area, the permanently connected appliances, and the larger of the heating or cooling load. NEC 220.82, the optional method, counts the general loads at full nameplate, takes the first 10 kVA at 100 percent and the remainder at 40 percent, then adds the governing heating or cooling figure. The result is divided by 240 volts to give amps, and rounded up to the next standard rating. Most single family houses land between 100 and 200 amps.

What is the difference between NEC 220.82 and 220.83?

220.82 sizes a service from scratch, which is what you need for new construction or a full service replacement. 220.83 asks a narrower question: whether the service already on the house carries a new load such as an EV charger or a heat pump. They use different demand factors and give different answers, and an inspector will expect 220.83 for an add-on job.

Does the optional method use the range and dryer demand tables?

No. Under NEC 220.82(B) appliances count at their full nameplate rating. Table 220.55 for cooking equipment and the 5,000 VA minimum in 220.54 for clothes dryers apply to the standard calculation in Part III, not to the optional method. This is a common source of two different but equally correct answers for the same house.

How does the 2026 NEC change a residential load calculation?

Three things, and they do not all pull the same way. The general lighting unit load drops from 3 to 2 VA per square foot. The first demand tier drops from 10 kVA to 8 kVA at 100 percent. EV charging equipment moves into a new part 120.82(D) at 100 percent, outside the demand tiers, where before it was swept in with the other appliances at the tiered rate. Washington adopts the 2026 NEC with an effective date of 31 December 2026.

Why does the calculator ask how many separately controlled heating units there are?

Because the demand factor depends on it. NEC 220.82(C)(4) takes electric space heating at 65 percent where there are fewer than four separately controlled units, and 220.82(C)(5) takes it at 40 percent where there are four or more. That is a 25 point swing on the heating load, so the count cannot be assumed. It is counted per dwelling unit, not per building.

Is a load calculation required for a permit?

In Washington a load calculation is generally required to support a new service or a service upgrade permit, and the authority having jurisdiction has the final say on the method and the figures. This calculator is a planning estimate. It is not a permit submittal and does not replace a licensed electrician evaluating the installation on site.

What size electrical service does this house need?

A full NEC load calculation, starting from nothing. Square footage, the appliances, the heating, and anything you plan to add.

Which calculation this is. The optional method for a dwelling unit, NEC Article 220.82. It sizes a service that does not exist yet. If instead you are adding one thing to a service you already have, the EV charger and heat pump calculators use the existing dwelling method, NEC 220.83, which is the one an inspector will expect for that job.

Important disclaimer. This calculator is provided for general estimation purposes only and does not constitute professional electrical advice, engineering analysis, or a code compliance determination. Results are based on what you enter, under the NEC Article 220.82 optional method for the code edition you select. Actual loads, service sizing requirements and upgrade needs vary with specific appliance nameplate ratings, utility requirements, local amendments to the NEC, physical inspection of existing wiring, and other site conditions this tool cannot assess. No electrical work should be planned, permitted, or performed based solely on the results of this calculator. Hanco Electric LLC assumes no liability for decisions made from this output. Always consult a licensed electrician for a proper load calculation and an on-site evaluation.

I understand this is an estimate only and will consult a licensed electrician before making any electrical decisions.

Before you start

Use nameplate ratings wherever you have them. The optional method counts appliances at their full nameplate value, so a real number beats a good guess every time. Where you do not have one, there is an estimate option and the result will tell you which figures were estimated.

One thing worth knowing up front. The optional method does not use the range and dryer demand tables. Under 220.82 a range counts at its full nameplate rating, not the reduced Table 220.55 figure, and there is no 5,000 VA dryer minimum. That is why this calculation can come out differently from one done the standard way, and both are correct.

1. Which code edition

Washington adopts the 2026 NEC on 31 December 2026. Three things change for this calculation, and all three pull in different directions, so it is worth running both if your work lands near that date. The general lighting load drops from 3 to 2 VA per square foot, the first demand tier drops from 10 kVA to 8 kVA, and EV charging equipment moves out of the demand tiers into its own part at 100 percent.

2. The house

Floor area, sq ft *

How many kitchens Each kitchen carries two small appliance circuits at 1,500 VA each, so a second kitchen adds 3,000 VA before a single appliance is counted. An ADU or a mother-in-law unit with its own cooking counts. A wet bar usually does not.

How many laundry circuits 1,500 VA each. Nearly every house has one. Enter 0 only if there is genuinely no laundry circuit.

3. The big appliances

Gas appliances draw nothing electrically, so a house on a gas range has more room than the same house all electric. Enter these at full nameplate. Under the optional method the range is not reduced by Table 220.55 and the dryer has no minimum.

4. Kitchen appliances

The two small appliance circuits already cover whatever is plugged into them. An appliance only counts separately if it is built in, hardwired, or on its own breaker. A countertop microwave on a kitchen outlet is already counted. An over-the-range one is not. If you are unsure, check it anyway: that is the cautious side and it will not undersize you.

5. Heating and cooling

Heating and cooling never run at the same time, so the code counts only the larger of the two. Article 220.82(C) compares six different ways of working out that figure and takes whichever is biggest, so entering everything you have is safe.

What heats the house *

The heat pump

Do you have the outdoor unit nameplate? *

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. On mini-splits and most newer inverter units there is no RLA line, so 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, and using one of them will oversize the answer.

Does it have backup electric heat? *

Ductless mini-splits usually have none. A ducted system replacing a furnace usually does, and on a quote it is called auxiliary or backup heat. Where it exists it is normally the number that decides the answer, not the outdoor unit.

Backup heat, kW *

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

An outdoor thermostat or a lockout relay. Where the two are interlocked, 220.82(C)(3) lets the compressor drop out of the sum and keeps the backup heat at 65 percent. It changes the number a lot, and it is a control change rather than a service change. If you are not sure, leave it on "do not know" and the calculation takes the larger, cautious reading.

Thermal storage, kW * Electric thermal storage and other heating designed to run continuously counts at 100 percent under 220.82(C)(6), with no reduction.

Air conditioning

Separate central air conditioning

Only for a separate cooling unit. A heat pump is one machine that both heats and cools, so do not enter it twice.

6. EV charging

There is or will be an EV charger

7. Anything else

Sauna, pool or well pump, shop subpanel, welder, second panel. Anything fastened in place or permanently connected that the lists above missed. Use the nameplate figure rather than an estimate of what you think it draws. Leave heating and cooling out of this section, since section 5 already has them.

Yes, there is something else

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