HVAC
HVAC Electricity Cost Calculator
Work out what a system costs to run in electricity, from its draw, its run hours and the tariff.
Result
Nameplate wattage is the maximum draw. Modulating and variable-speed equipment averages well below it, so this is an upper bound for those systems.
Get a Free Business AuditWhat moves the number
- Actual draw under load rather than nameplate amps.
- Run hours across the season, which dominate the total.
- Tariff structure, since time of use and demand charges change the answer materially.
Where this one goes wrong
Ignoring auxiliary or emergency heat on a heat pump. Resistance backup draws heavily and runs exactly when the customer is watching the bill, and a running cost estimate that omits it will be wrong in winter.
Questions
About this calculator
Why is my heat pump expensive in cold weather?
Usually auxiliary resistance heat. As outdoor temperature falls the heat pump's capacity drops and backup heat makes up the difference, and resistance heat is far more expensive per unit delivered.
Do demand charges matter?
On commercial tariffs, considerably. A short peak can set a charge for the whole month, which makes staging and controls more valuable than the headline efficiency.
Should I use nameplate amps?
Only as a ceiling. Actual draw varies with conditions and staging, and using the nameplate figure overstates running cost, sometimes substantially.
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 3,500.
- Hours per day. Enter your own figure; the page starts at 10.
- Days. Enter your own figure; the page starts at 30.
- Electricity rate per kWh ($). Enter your own figure; the page starts at $0.16.
- Fixed charges for the period ($). Enter your own figure; the page starts at $12.
The result updates as you type, so you can try a figure, see what it does to total cost, 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) | 3,500 |
| Hours per day | 10 |
| Days | 30 |
| Electricity rate per kWh | $0.16 |
| Fixed charges for the period | $12 |
What comes out
| Result | Value |
|---|---|
| Total cost main result | $180.00 |
| Energy used | 1,050.0 |
| Cost per day | $6.00 |
| Annualised cost | $2,190 |
That equipment uses 1,050.0 kWh over 30 days, costing $180.00, about $6.00 a day.
How sensitive the answer is
Holding everything else steady and changing only electricity rate per kwh, this is what happens to total cost. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Electricity rate per kWh ($) | Total cost |
|---|---|
| $0.08 | $96.00 |
| $0.12 | $138.00 |
| $0.16 example above | $180.00 |
| $0.24 | $264.00 |
| $0.32 | $348.00 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Power draw (watts)
- A number, between 0 and 100000, starting at 3,500.
- Hours per day
- A number, between 0 and 24, starting at 10.
- Days
- A number, between 0 and 366, starting at 30.
- Electricity rate per kWh ($)
- A money amount, starting at $0.16.
- Fixed charges for the period ($)
- A money amount, starting at $12.
What the results tell you
| Result | What it is |
|---|---|
| Total cost | The headline result. A money figure. |
| Energy used | A decimal figure. |
| Cost per day | A money figure. |
| Annualised cost | A money figure. |
Before you rely on this number
Sizing, capacity and load figures here are planning estimates. A real installation depends on the manufacturer's data for the specific equipment, the duct system it is going into, and a proper load calculation for the building. Use this to sanity-check a number or price a job, not to select equipment.
Keep going
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