Watt to Watt-Hour Calculator
Convert between watts and watt-hours over time
Table of Contents
How to Use
- Select conversion direction: Watts to Watt-hours or Watt-hours to Watts
- Enter power in watts (for Watts to Wh) or energy in watt-hours (for Wh to Watts)
- Enter time duration and select time unit (hours, minutes, seconds, or days)
- Optionally enter electricity rate to estimate cost
- Click calculate to see energy in Wh and kWh, or power in watts
Understanding Watts and Watt-Hours
Watts (W) measure power - the rate at which energy is used or produced at any given moment. Watt-hours (Wh) measure energy - the total amount of power consumed or produced over time. The relationship is: Energy (Wh) = Power (W) × Time (hours).
For example, a 100W light bulb running for 10 hours consumes 1,000 Wh (or 1 kWh) of energy. Understanding this conversion is essential for calculating electricity costs, sizing batteries, and managing energy consumption.
Conversion Formulas
The conversion between watts and watt-hours depends on time:
- Energy (Wh) = Power (W) × Time (hours)
- Power (W) = Energy (Wh) ÷ Time (hours)
- 1 kWh = 1,000 Wh
- 1 Wh = 3,600 joules
Practical Applications
Understanding the watt to watt-hour conversion has many real-world applications:
- Calculating electricity bills based on appliance power ratings and usage time
- Sizing solar panels and battery systems for off-grid power
- Estimating runtime of battery-powered devices
- Comparing energy efficiency of different appliances
- Planning electrical system capacity for homes and businesses
- Understanding energy consumption patterns for cost savings
Common Examples
| Device | Power (W) | Usage Time | Energy (Wh) |
|---|---|---|---|
| LED Light Bulb | 10 W | 8 hours | 80 Wh |
| Laptop Computer | 65 W | 6 hours | 390 Wh |
| Refrigerator | 150 W | 24 hours | 3,600 Wh (3.6 kWh) |
| Space Heater | 1,500 W | 3 hours | 4,500 Wh (4.5 kWh) |
| Phone Charger | 5 W | 2 hours | 10 Wh |
Frequently Asked Questions
- What is the difference between watts and watt-hours?
- Watts measure power (rate of energy use), while watt-hours measure energy (total amount used over time). Think of it like speed vs. distance: watts tell you how fast you're using energy, watt-hours tell you how much total energy you've used.
- How do I calculate watt-hours from watts?
- Multiply the power in watts by the time in hours: Watt-hours = Watts × Hours. For example, a 100W device running for 5 hours uses 500 Wh of energy.
- How do I convert watt-hours to kilowatt-hours?
- Divide watt-hours by 1,000 to get kilowatt-hours (kWh). For example, 2,500 Wh = 2.5 kWh. Electricity bills typically use kWh for larger energy amounts.
- How can I estimate my electricity cost from watt-hours?
- First convert Wh to kWh (divide by 1,000), then multiply by your electricity rate per kWh. For example, 3,000 Wh = 3 kWh. At $0.12 per kWh, the cost is 3 × $0.12 = $0.36.
- Why is understanding watt-hours important for solar and battery systems?
- Battery capacity is measured in watt-hours (or amp-hours). Knowing how many watt-hours your devices consume helps you size your battery bank and solar panels correctly to meet your energy needs.