Dwelling Load Calculator

Last updated: Jun 16, 2026

Size a single-family electrical service from its loads, using the NEC Article 220 standard and optional methods.Learn more ▾Show less ▴

This calculator totals a home's electrical demand the way the National Electrical Code does and recommends the minimum service size in amps. Enter the floor area, branch circuits, appliances, cooking equipment, dryer, and heating or cooling, then choose the Standard calculation (Part III, with each demand factor applied separately) or the Optional calculation (220.82, for services of 100 amps or more). The result shows the total calculated load, the demand in amps, and the next standard service size, with a full line-by-line breakdown.

Standard ?The electrical code to calculate against: NEC (US/Canada), BS 7671 (UK/IET), or AS/NZS 3000 (Australia/New Zealand). Each uses a different method.

Method ?The electrical code to calculate against: NEC (US/Canada), BS 7671 (UK/IET), or AS/NZS 3000 (Australia/New Zealand). Each uses a different method.

Floor area ?Habitable floor area in square feet, using outside dimensions. Exclude open porches, garages, and unused or unfinished spaces not adaptable for future use.

ft²

Small-appliance circuits ?Number of 20-amp small-appliance branch circuits serving the kitchen, dining, and similar areas. The code requires at least two; each counts as 1500 VA.

Laundry circuits ?Number of dedicated laundry branch circuits. At least one is required for a dwelling; each counts as 1500 VA.

Fastened-in-place appliances ?Permanently connected appliances such as a water heater, dishwasher, disposal, or compactor, entered at nameplate VA. Do not list the range, dryer, heating, or A/C here — they are entered separately. Four or more such appliances get a 75% demand factor.

Cooking equipment

Number of ranges ?How many household ranges, cooktops, or wall ovens. Leave at 0 if the home has no electric cooking equipment (e.g. gas range).

Rating each (kW) ?Nameplate rating of each cooking unit in kilowatts. The tool applies NEC Table 220.55 — one range up to 12 kW is counted as 8 kW.

Electric dryer

Number of dryers ?How many household electric clothes dryers. Leave at 0 for a gas dryer or none.

Rating each (VA) ?Nameplate rating of each dryer in VA. The code counts each at 5000 VA or nameplate, whichever is larger, so leaving this blank uses the 5000 VA minimum.

Heating & cooling

Air conditioning ?Total air-conditioning load in VA (compressor plus air handler). Heating and cooling are noncoincident — only the larger of the two is counted.

Electric heating ?Total electric heating load in VA. Only the larger of heating or air conditioning is included in the calculation.

Heating type ?Used by the optional method: central electric furnaces and systems of fewer than four units are taken at 65%, four or more separately controlled units at 40%, and heat pumps at 100%.

Largest motor (standard method)

Largest motor ?VA of the largest motor in the calculation (often the A/C compressor, or a disposal if A/C is dropped). NEC 220.50 adds 25% of the largest motor. Used by the standard method only.

Lighting ?Total connected lighting load in VA at 230 V. Fluorescent and discharge lamps are entered at their full connected load. Diversity of 66% is applied.

Cooker ?Connected load of the cooking appliance in VA. Diversity: the first 10 A at 100%, then 30% of the remainder.

Socket in cooker unit ?Tick if the cooker control unit incorporates a socket-outlet — this adds a fixed 5 A to the cooker demand.

Instantaneous water heaters / showers ?Total connected load of instantaneous water heaters and electric showers in VA. The two largest are taken at 100%, the rest at 25%.

Thermostatic water heater (immersion) ?Connected load of thermostatically controlled (immersion) water heating in VA. No diversity — taken at 100%.

Space heating (storage / floor) ?Connected load of thermal-storage or floor space heating in VA. No diversity — taken at 100%.

Other heating & power ?Other heating and power loads not listed above, in VA. Diversity: 100% up to 10 A, then 50% of the remainder.

Socket / final circuits ?The rated current (A) of each ring or radial final circuit. Diversity: 100% of the largest circuit + 40% of every other circuit.

Lighting points ?Number of lighting points. Demand: 3 A for the first 20 points, plus 2 A for each additional 20 points or part. Lighting track counts as 2 points per metre.

Outdoor lighting over 1000 W ?Connected load of outdoor/floodlighting exceeding 1000 W total, in VA. Taken at 75%.

10 A socket-outlet points ?Number of 10 A socket-outlet points (a double socket counts as 2). Demand: 10 A for the first 20 points, plus 5 A per additional 20 or part.

15 A socket-outlets present ?Number of 15 A socket-outlets. If any are present, 10 A is added (or 15 A if 20 A outlets are also present).

20 A socket-outlets present ?Number of 20 A socket-outlets. If any are present, 15 A is added (this takes precedence over the 15 A socket addition).

Ranges / cooking (over 10 A) ?Connected load of ranges, cooking, or laundry appliances rated over 10 A, in VA. Taken at 50%.

Space heating or A/C (larger) ?Connected load of fixed space heating or air-conditioning over 10 A, in VA. Heating and cooling are noncoincident — enter only the larger. Taken at 75%.

Instantaneous water heaters ?Connected load of instantaneous water heaters in VA. Taken at 33.3%.

Storage water heaters ?Connected load of storage water heaters in VA. Taken at full load (100%).

EV charging ?Connected load of electric-vehicle charging equipment in VA. Taken at full connected load (100%).

Load breakdown

Load	VA

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About This Tool

The Dwelling Load Calculator sizes the electrical service for a single-family home by totaling its demand under NEC Article 220. It applies the code's demand factors to lighting, appliances, cooking, the dryer, and heating or cooling, then recommends the minimum standard service size so electricians, inspectors, and homeowners can plan a service or upgrade with confidence.

Sources: NEC (NFPA 70) · BS 7671 (IET) · AS/NZS 3000:2018

How to Use

Choose the standard or optional method, then enter the floor area and the number of small-appliance and laundry circuits.
Add the fastened appliances, cooking equipment, dryer, and the heating and cooling loads.
Read the minimum service size, the total calculated load, and the line-by-line breakdown.

Methodology

Calculations follow NEC (NFPA 70) Article 220. The standard method takes 3 VA/ft² for general lighting plus 1500 VA per small-appliance and laundry circuit, applies the Table 220.42 demand factors (first 3000 VA at 100%, the next at 35%), adds fastened appliances (75% for four or more), the Table 220.55 range demand, the Table 220.54 dryer demand, the larger of heating or cooling (220.60), and 25% of the largest motor (220.50). The optional method (220.82) totals the general loads at nameplate, takes 100% of the first 10 kVA and 40% of the remainder, then adds the largest heating or cooling load. The total is divided by 240 V and rounded up to the next standard service size.

Sources: NEC Article 220 · Residential Service Calculations (IAEI)

Understanding Your Results

The headline figure is the minimum standard service size in amps. The calculated load is the total demand in volt-amperes; dividing it by 240 V gives the demand in amps, which is rounded up to the next standard size (100, 125, 150, 200, 225, 400 A and so on). The breakdown shows where the load comes from. A result close to the next size up is worth revisiting if you expect to add large loads later, such as an electric-vehicle charger or a heat pump.

Sources

NEC (NFPA 70) — National Electrical Code, Article 220
BS 7671:2018 — IET Wiring Regulations (maximum demand & diversity)
AS/NZS 3000:2018 — Wiring Rules, Appendix C (maximum demand)

Practical Examples

Example 1 (standard): a 3700 ft² home with five small-appliance circuits, two laundry circuits, several fastened appliances, a 6 kW dryer, two cooking appliances, and 16 kW of electric heat calculates to about 48,627 VA — 202.6 A — which rounds up to a 225 A service. Example 2 (optional): a 2800 ft² home with a 14 kW range, a 5 kW dryer, a water heater, a dishwasher, and 15 kW of central electric heat calculates to 30,310 VA — 126.3 A — a 150 A service.

Service sizing tips

• Run both methods. The optional calculation often returns a smaller service for all-electric homes; the standard method can be required for unusual layouts. • Count every fastened appliance — water heater, dishwasher, disposal, compactor. Four or more earn the 75% demand factor. • A single range up to 12 kW is only 8 kW of demand, so a big nameplate rating rarely drives the service size. • Heating and cooling never add together — only the larger counts. • Leave headroom. If you plan to add an EV charger or heat pump, size the service for the future load now rather than upgrading twice.

All calculations are performed locally in your browser. No data is sent to any server.

Frequently Asked Questions

What is a dwelling load calculation?

A dwelling load calculation totals the electrical demand of a home — lighting, receptacles, appliances, cooking equipment, a dryer, and heating or cooling — to determine the minimum size of the electrical service or feeder. The National Electrical Code requires it before installing or upgrading a service so the panel and conductors are neither undersized nor needlessly oversized.

What is the difference between the standard and optional methods?

The Standard method (NEC 220 Part III) sizes each category separately and applies individual demand factors, including Table 220.55 for ranges. The Optional method (220.82), available for dwellings served at 100 amps or more, lumps most loads together and applies 100% to the first 10 kVA and 40% to the remainder, then adds the largest heating or cooling load. The optional method is usually simpler and often yields a smaller result. This tool computes both.

What does the 3 VA per square foot cover?

NEC 220.41 assigns 3 volt-amperes per square foot of habitable floor area for general lighting and general-use receptacles. You do not count individual lights and outlets separately — the 3 VA/ft² figure covers them. Two small-appliance branch circuits (1500 VA each) and at least one laundry circuit (1500 VA) are added on top, then the general-lighting demand factors are applied.

How is the electric range load calculated?

Ranges use NEC Table 220.55. For one range up to 12 kW the demand is 8 kW, regardless of the higher nameplate rating; larger or multiple ranges follow Column C and its notes (for example, a single range over 12 kW adds 5% per kW above 12). Smaller cooking appliances rated 1.75–8.75 kW use the Column A or B percentages instead. The tool applies the correct column automatically.

How is the clothes dryer load handled?

NEC 220.54 sets each household electric dryer at 5000 VA or its nameplate rating, whichever is larger. For multiple dryers a demand factor from Table 220.54 reduces the total. A single dryer is therefore counted at a minimum of 5000 VA. The optional method instead counts the dryer at its nameplate within the general load bucket.

Why are heating and air conditioning not added together?

NEC 220.60 treats heating and air conditioning as noncoincident loads because a home does not heat and cool at the same time. Only the larger of the two is included in the calculation; the smaller is dropped. In the optional method, electric space heating is taken at a reduced percentage (65% for fewer than four units, 40% for four or more), while air conditioning is taken at 100%, and the larger result is used.

What service size do I need?

Divide the total calculated load in volt-amperes by 240 volts to get the demand in amps, then round up to the next standard service size — typically 100, 125, 150, 200, 225, or 400 amps. This tool does the rounding for you. Most modern single-family homes land on a 150 or 200 amp service; larger homes with electric heat can require 225 amps or more.

Is this calculator code-compliant for permits?

It faithfully implements the NEC Article 220 standard and optional methods and is validated against published worked examples, but it is an estimating aid, not a substitute for a licensed electrician or your local authority having jurisdiction. Local amendments, service-conductor sizing rules, and project specifics can change the result. Always have a final calculation reviewed and stamped where required.

Is my data private?

Yes. The calculator runs entirely in your browser. The home details you enter are never uploaded, stored on a server, or shared. It keeps working offline once the page has loaded, and a shared link only includes your inputs if you choose to copy it.