Enter both values to calculate watts
Kilowatt Hours (kWh)
Hours (h)
Watts (W)
Result will appear here
Understanding Energy vs Power
The relationship between kilowatt hours and watts involves time:
- Energy (kWh) = Power (W) × Time (h) ÷ 1000
- Power (W) = Energy (kWh) × 1000 ÷ Time (h)
For Your Electric Bill
Understanding these relationships helps you:
- Estimate costs - Know how much devices cost to run
- Size solar panels - Match production to consumption
- Compare appliances - Understand energy efficiency ratings
- Track usage - Break down your monthly bill
Real-World Solar Examples
Average US Home Power Draw
The average US home uses about 30 kWh per day. Over 24 hours, the average draw is 1,250W. But solar only produces during daylight, so the required array is much larger.
Sizing Solar Panels for Daily Production
To produce 30 kWh per day with 5 peak sun hours, you need 6,000W of solar panels. After accounting for 15–25% system losses, a realistic array is 7–7.5 kW.
Tesla Powerwall Discharge Rate
A 13.5 kWh Powerwall discharged evenly over 10 hours provides 1,350W continuous. But discharging in 2 hours requires 6,750W — exceeding its 5,000W continuous rating.
When You'll Need This Conversion
- Translating a Utility Bill to Array Size — A bill showing 750 kWh/month means 25 kWh/day. With 4.5 peak sun hours: 5,556W needed. An installer recommends 6.5–7 kW to account for ~20% system losses.
- Checking If an Inverter Can Handle Loads — Running loads that consume 8 kWh over 4 hours averages 2,000W. But peak loads may spike to 3,500–4,000W when multiple appliances run simultaneously — requiring at least a 4 kW inverter.
- Generator Backup Calculations — An off-grid system normally produces 6 kWh from solar. On cloudy days, a 3,000W generator compensates in 2 hours of run time, using about 1 gallon of fuel.
Solar Tips & Common Mistakes
Peak Sun Hours ≠ Daylight Hours: Use peak sun hours (typically 4–6 for most US locations), not total daylight hours (10–14). A 400W panel in 5 peak sun hours produces 2,000Wh, not the 5,600Wh from 14 daylight hours.
Average Power Hides Dangerous Peaks: A home averaging 1,250W may peak at 8,000–10,000W when the AC, stove, and dryer start simultaneously. Always size inverters and breakers for peak, not average.
Monthly kWh Varies Seasonally: Summer AC usage may push consumption above 40 kWh/day, while spring/fall may be 20 kWh/day. Design for the worst-case month, or accept partial offset in peak months.
Solar Calculators
Related Conversion Calculators
Last updated: January 5, 2026
