Watt Hour Calculator
Free watt hour calculator to convert watts to watt-hours, estimate battery runtime, calculate electricity costs, and size solar panel systems. Plan your energy needs accurately.
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Calculate Energy in Watt Hours
Understanding watt hours is essential for sizing batteries, estimating electricity costs, and planning solar systems. Our calculator handles everything from basic Wh calculations to full solar panel sizing with battery recommendations.
Understanding Watt Hours
A watt hour (Wh) measures energy consumption over time. It's calculated by multiplying power (watts) by time (hours). A 100W device running for 5 hours uses 500Wh or 0.5kWh. This unit helps compare batteries, calculate electricity bills, and size renewable energy systems.
Watt Hour Formula
Wh = Watts × HoursWhy Watt Hours Matter
Battery Capacity Planning
Choose the right portable power station or UPS by matching battery Wh capacity to your device requirements.
Electricity Cost Control
Identify energy-hungry appliances and calculate their monthly/yearly operating costs.
Solar System Design
Properly size solar panels and batteries based on daily energy needs and available sunlight.
How to Use the Watt Hour Calculator
Common Watt Hour Calculations
Laptop on Power Station
50W laptop on 500Wh battery = 8.5 hours runtime (at 85% efficiency).
Mini Fridge Running Cost
50W mini fridge × 24h × 30 days = 36kWh/month ≈ $4.30 at $0.12/kWh.
Home Solar Setup
5000Wh daily use ÷ 5 sun hours = 1250W solar panels needed (plus 20% buffer).
RV Battery Bank
400Wh daily use × 2 days autonomy = 800Wh minimum battery capacity.
Frequently Asked Questions
Watts (W) measure power - how fast energy is used. Watt hours (Wh) measure total energy consumed. A 100W bulb uses 100 watts of power; running it for 10 hours uses 1000Wh (1kWh) of energy.