Solar Panel Watts Calculator
Calculate the solar panel wattage you need for your specific appliances. Add or remove devices, adjust usage hours, and get system size and off-grid battery bank recommendations.
Appliance List
| Appliance | Watts | Hours/Day | Daily Wh | |
|---|---|---|---|---|
| 3,600 | ||||
| 500 | ||||
| 500 | ||||
| 480 | ||||
| 1,200 | ||||
| 500 | ||||
| 12,000 |
How It Works
This appliance load calculator helps you size a solar system based on your actual device usage:
- Daily consumption: Each appliance's wattage is multiplied by its daily usage hours to calculate watt-hours (Wh). All appliances are totaled for your daily energy needs.
- System sizing: Daily Wh is divided by your location's peak sun hours and an 80% efficiency factor. This accounts for inverter losses, wiring losses, temperature effects, and panel soiling.
- Battery bank (off-grid): For off-grid systems, the battery capacity is calculated by dividing daily Wh by 85% inverter efficiency and 50% depth of discharge (DoD). This ensures batteries aren't over-discharged, extending their lifespan.
Add or remove appliances and adjust watts and hours to match your actual usage. The default list covers common household devices with typical wattage ratings.
Frequently Asked Questions
How do I calculate solar panel wattage for my needs?
List each appliance's wattage and daily usage hours. Multiply watts by hours to get daily watt-hours (Wh). Total all appliances, then divide by your location's peak sun hours and 0.8 (system efficiency) to get the recommended system size in watts.
What size battery bank do I need for off-grid solar?
For off-grid systems, take your total daily Wh consumption and divide by inverter efficiency (85%) and depth of discharge (50% for lead-acid, 80-90% for lithium). This gives you the minimum battery bank capacity. Adding 1-2 days of autonomy is recommended for cloudy days.
Why is the recommended system larger than my daily usage?
Solar panels don't produce at full capacity all day. The calculation divides your daily needs by peak sun hours (typically 3.8-6.5 hours depending on location) and applies an 80% efficiency factor to account for real-world losses from inverter conversion, wiring, temperature, and panel soiling.
How do I find the wattage of my appliances?
Check the label on the back or bottom of the appliance for its wattage rating. You can also use a Kill-A-Watt meter to measure actual consumption. Note that some appliances (like refrigerators and AC units) cycle on and off, so their average draw is lower than the rated watts.