What this result means
This calculator converts watts and hours into kilowatt-hours, then multiplies by the electricity price. The results panel explains the main number and the quantities that produced it, so you can check whether the estimate answers your real question.
Formula used
kWh = Watts ÷ 1,000 × hours per day × days. Cost = kWh × price per kWh.
Step-by-step calculation
- Validate every required value and reject values outside the stated field limits.
- Convert rates and time periods to the units required by the formula.
- Calculate with full JavaScript number precision; do not round intermediate values.
- Round only the displayed result and explain the practical meaning.
Worked example
A 1,500 W appliance used 2 hours daily for 30 days consumes 90 kWh; at $0.20/kWh it costs $18.
Assumptions and limitations
- Power draw is constant while operating.
- The entered price represents the relevant unit rate.
- Standing charges, tiered rates, and taxes are excluded.
How to use this calculator
- Choose a currency symbol when the tool uses money.
- Enter values in the units shown beside each field.
- Select Calculate, then read both the main result and interpretation.
- Change one uncertain input at a time to understand sensitivity.
- Use Copy result or Share only when you choose to move the result outside this page.
Common mistakes
- Treating watts as kilowatts.
- Forgetting standby use.
- Ignoring tiered tariffs.
Frequently asked questions
What is a kilowatt-hour?
It is one kilowatt used for one hour.
Does this include fixed charges?
No.
Can I compare appliances?
Yes, calculate each with the same usage assumptions.
Related calculators and guides
Methodology and sources
Formula definitions and edge-case behavior are documented on our Methodology page. No external data is fetched by this calculator.
See the site-wide calculation methodology and editorial standards. Formula errors can be reported through the error-reporting instructions.