Watt Hour Calculator
Calculate electrical energy in watt-hours. This tool converts watts and hours or amp-hours and volts into watt-hours for battery sizing and energy planning.
Energy in Wh Tool
Choose a calculation mode to find watt-hours from power and time or from battery amp-hours and voltage.
Watt Hour Estimator
Watt-hours are a core battery and energy unit because they show the total amount of energy, not just power or capacity alone.
Calculation Results
These results show total watt-hours and the same value converted into kilowatt-hours for easier comparison.
Educational Estimates Only: Real energy use can vary due to efficiency losses, voltage sag, inverter losses, and duty cycles. Always verify with measured values or datasheets for critical use.
Wh Basics
Watt-hours are a simple way to measure energy and compare batteries or loads across different voltages and use times.
A watt-hour is the amount of energy used by one watt over one hour. It is a core battery unit because it shows actual stored or consumed energy, not just voltage, current, or power alone.
These formulas show two common ways to calculate energy. If you know device power and time, multiply watts by hours. If you know battery capacity and voltage, multiply amp-hours by volts. This makes watt-hours useful for comparing battery energy across different voltages.
For example, 100W × 5h = 500Wh, 20W × 10h = 200Wh, and 100Ah × 12V = 1200Wh. In each case, the result describes total energy over time rather than instant power alone.
Wh formula
- Wh = W × h.
- Wh = Ah × V.
- Energy is power over time.
- Core battery unit.
Examples
- 100W × 5h = 500Wh.
- 20W × 10h = 200Wh.
- 100Ah × 12V = 1200Wh.
What is a watt-hour?
It is the energy used by 1 watt for 1 hour. You can think of it as a small energy unit that helps compare appliances, battery packs, and electrical loads.
Why use Wh?
Watt-hours let you compare battery energy across different voltages. Two batteries may have different Ah values, but Wh shows the real stored energy more clearly.
Frequently Asked Questions
These are common questions about watt-hours, battery energy, and power-over-time calculations.
What is a watt-hour?
Energy used by 1 watt for 1 hour.
Why use Wh?
Wh lets you compare battery energy across different voltages.
How do I calculate Wh from watts and hours?
Multiply watts by hours. For example, 100W used for 5 hours equals 500Wh.
How do I calculate Wh from Ah and volts?
Multiply amp-hours by volts. For example, 100Ah at 12V equals 1200Wh.
Is Wh the same as watts?
No. Watts measure power at a moment, while watt-hours measure energy over time.
Is Wh the same as Ah?
No. Amp-hours measure charge, while watt-hours include voltage and show total energy more clearly.
How many Wh are in 1 kWh?
1 kilowatt-hour equals 1000 watt-hours.
Why is Wh useful for batteries?
Because it helps compare stored energy across batteries that may use different voltages and capacities.
Can I use Wh to estimate runtime?
Yes. Divide available watt-hours by the load in watts to estimate runtime in hours, though real losses may reduce the result.
Is this energy estimate exact?
No. Real systems can lose energy due to heat, conversion losses, and real-world battery behavior.
Compare Energy More Clearly
Use this calculator to convert power or battery values into watt-hours, then compare related tools to plan capacity and runtime more accurately.
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