Electrical
Electrical Load Calculator
Build an early dwelling-load estimate from floor area and major appliances, then identify what a formal service calculation still needs.
Result
Electrical work is life-safety work governed by the NEC or your local code, and must be designed and installed by a licensed electrician. Conductor and overcurrent sizing depends on ambient temperature, conductor bundling, termination ratings, continuous-load rules and more. This is an educational estimate and must never be used as the basis for an installation. This follows the shape of the NEC Article 220 standard method but simplifies it considerably: range demand factors, dryer minimums, largest-motor rules and the optional calculation method all change the result. A licensed electrician must perform the actual load calculation.
Get a Free Business AuditWhat moves the number
- Floor area and the entered appliance loads establish the connected-load starting point.
- Demand assumptions differ from simply adding every nameplate.
- Heating, cooling and planned additions affect the load schedule that needs review.
Where this one goes wrong
This simplified model omits parts of a complete dwelling calculation. A suggested service size is not approval to add an EV charger or replace a service. Spare panel spaces and unused amperage are different questions.
Questions
About this calculator
Why is demand lower than connected load?
Demand methods recognize that specified loads are not all assessed identically. The permissible method and its conditions must come from the adopted code, rather than an arbitrary diversity discount.
Can my utility bill establish service capacity?
Energy consumed over a billing period does not reveal every coincident peak. Approved demand records and a formal load assessment answer different questions.
Does this replace an electrician's calculation?
No. It is a planning check for a code-governed design, with appliance details, local amendments and utility requirements still to resolve.
The formula
general lighting = 3 VA per sq ft; first 3,000 VA at 100%, remainder at 35%; plus appliance and HVAC loads
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How to use this calculator
- Floor area (sq ft) (sq ft). Enter your own figure; the page starts at 2,000 sq ft.
- Small-appliance circuits. Kitchen circuits, minimum two required.
- Range / cooktop (watts). Enter your own figure; the page starts at 8,000.
- Dryer (watts). Enter your own figure; the page starts at 5,000.
- HVAC (watts). Enter your own figure; the page starts at 6,000.
- Other fixed appliances (watts). Enter your own figure; the page starts at 4,500.
The result updates as you type, so you can try a figure, see what it does to suggested service size, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Floor area (sq ft) | 2,000 sq ft |
| Small-appliance circuits | 2 |
| Range / cooktop (watts) | 8,000 |
| Dryer (watts) | 5,000 |
| HVAC (watts) | 6,000 |
| Other fixed appliances (watts) | 4,500 |
| Service voltage (V) | 240 |
What comes out
| Result | Value |
|---|---|
| Suggested service size main result | 150 A service |
| Calculated load | 121.4 |
| Demand load after derating | 29,125 |
| Total connected load | 34,000 |
Demand load is about 29,125 W, or 121.4 amps at 240 V, pointing to a 150 A service.
How sensitive the answer is
Holding everything else steady and changing only floor area (sq ft), this is what happens to suggested service size. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Floor area (sq ft) (sq ft) | Suggested service size |
|---|---|
| 1,000 sq ft | 150 A service |
| 1,500 sq ft | 150 A service |
| 2,000 sq ft example above | 150 A service |
| 3,000 sq ft | 150 A service |
| 4,000 sq ft | 150 A service |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Floor area (sq ft) (sq ft)
- Measured in sq ft, starting at 2,000 sq ft.
- Small-appliance circuits
- Kitchen circuits, minimum two required.
- Range / cooktop (watts)
- A number, between 0 and 100000, starting at 8,000.
- Dryer (watts)
- A number, between 0 and 100000, starting at 5,000.
- HVAC (watts)
- A number, between 0 and 200000, starting at 6,000.
- Other fixed appliances (watts)
- A number, between 0 and 200000, starting at 4,500.
- Service voltage (V)
- A number, between 0 and 1000, starting at 240.
What the results tell you
| Result | What it is |
|---|---|
| Suggested service size | The headline result. A category or planning selection, rather than a measured quantity. |
| Calculated load | A decimal figure. |
| Demand load after derating | A number. |
| Total connected load | A number. |
Before you rely on this number
Conductor sizing, voltage drop and load figures are governed by code, and the code takes precedence over any calculator. Ambient temperature, conduit fill, continuous load factors and the specific installation all change the answer. Treat this as a first pass, not a design.
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