Electrical
kWh Calculator
Turn measured or estimated operating watts into energy use over a defined schedule and equipment count.
Result
Nameplate wattage is a maximum. Thermostatically controlled and variable-speed equipment averages well below it, so treat this as an upper bound for those.
Get a Free Business AuditWhat moves the number
- Hours should represent time drawing the stated power, not merely time plugged in.
- Days and unit count define the period and fleet being modeled.
- Cycling and standby operation may need separate runs with different wattages.
Where this one goes wrong
A nameplate maximum multiplied by every available hour can overstate consumption for cycling equipment. Conversely, recording only active operation misses standby use. State how the power figure was obtained so later comparisons use the same basis.
Questions
About this calculator
How do I handle equipment that cycles?
Use measured average power across a representative period, or calculate active and idle states separately. Do not reduce both hours and power for the same cycling effect.
Is the annualized result a forecast?
It extends the entered pattern. Seasonal opening hours, production changes and shutdowns require a revised schedule before it becomes a budget.
Where do I enter the tariff?
This tool measures energy rather than price. Carry the kWh estimate to a cost calculation using the relevant rate and billing conditions.
The formula
kWh = watts ÷ 1,000 × hours × days
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How to use this calculator
- Power draw (watts). Enter your own figure; the page starts at 1,500.
- Hours per day. Enter your own figure; the page starts at 4.
- Days. Enter your own figure; the page starts at 30.
- Number of units. Enter your own figure; the page starts at 1.
The result updates as you type, so you can try a figure, see what it does to energy used, 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 |
|---|---|
| Power draw (watts) | 1,500 |
| Hours per day | 4 |
| Days | 30 |
| Number of units | 1 |
What comes out
| Result | Value |
|---|---|
| Energy used main result | 180.0 |
| Per day | 6.0 |
| Annualised | 2,190 |
| Equivalent heat | 614,186 |
That uses 180.0 kWh over 30 days, 6.0 kWh a day, or 2,190 kWh a year.
How sensitive the answer is
Holding everything else steady and changing only power draw (watts), this is what happens to energy used. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Power draw (watts) | Energy used |
|---|---|
| 750 | 90.0 |
| 1,125 | 135.0 |
| 1,500 example above | 180.0 |
| 2,250 | 270.0 |
| 3,000 | 360.0 |
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
- Power draw (watts)
- A number, between 0 and 10000000, starting at 1,500.
- Hours per day
- A number, between 0 and 24, starting at 4.
- Days
- A number, between 0 and 3650, starting at 30.
- Number of units
- A number, between 0 and 10000, starting at 1.
What the results tell you
| Result | What it is |
|---|---|
| Energy used | The headline result. A decimal figure. |
| Per day | A decimal figure. |
| Annualised | A number. |
| Equivalent heat | 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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