Solar System Designer Tools
Solar Appliance Load Calculator
Select your appliances from our library of 50+ common household devices to calculate your total daily energy consumption and find the minimum inverter size required for your solar system.
How to Calculate Your Solar Load
Accurately knowing your total load is the starting point for every other solar calculation. The formula is simple:
Daily Energy (Wh) = Sum of (Appliance Watts × Hours Used Per Day)
Then add 15–20% for inverter losses and phantom loads (standby power draw).
Common Appliance Wattage Reference
| Appliance | Typical Watts | Surge Watts |
|---|
| Refrigerator (medium) | 100–200W running | 800–1,200W |
| LED Light Bulb (10W) | 10W | — |
| Laptop Computer | 45–90W | — |
| 65" LED TV | 90–120W | — |
| Coffee Maker | 900–1,200W | — |
| Microwave (800W) | 1,100–1,400W | — |
| Well Pump (1/2 HP) | 750W running | 2,500–3,500W |
| Window AC (10,000 BTU) | 900–1,200W | 2,000–3,000W |
| Hair Dryer | 1,500–2,000W | — |
| Electric Kettle | 1,200–1,800W | — |
Inverter Sizing Guidelines
Your inverter must handle the peak surge demand — not just the running load. Many appliances with motors (pumps, fridges, AC units) draw 2–5× their running wattage for 1–3 seconds at startup.
- Pure Sine Wave inverter: Required for sensitive electronics, variable-speed motors, and AC appliances. Recommended for all modern systems.
- Modified Sine Wave inverter: Only suitable for simple resistive loads like incandescent lights and basic tools. Avoid for modern appliances.
- Size rule: Inverter continuous rating ≥ Total running load; surge rating ≥ largest single motor's startup current.
Frequently Asked Questions
How do I find the wattage of my specific appliances?
Check the nameplate label on the appliance (usually on the back or bottom) for watts or amps. If only amps are listed, multiply by your voltage: Watts = Amps × Volts. For AC appliances in North America, use 120V. Alternatively, use a Kill A Watt meter plugged into the outlet for the most accurate real-world measurement.
What size inverter do I need for a whole house?
A typical North American home uses 1,500–3,500W continuously, with peaks up to 7,000W when large appliances start simultaneously. For whole-home off-grid backup, a 6,000–10,000W pure sine wave inverter at 48V is typical. Use the appliance calculator to tally your specific loads rather than guessing.
Can I run a refrigerator on solar power?
Yes, easily. A standard 18 cu.ft. refrigerator uses about 1–1.5 kWh per day. You'd need about 200–400W of solar panels and a 100–200Ah battery bank to run it 24/7 off-grid in an average sunny location. Energy-efficient DC refrigerators (like Vitrifrigo or Isotherm models) use only 0.3–0.7 kWh/day.
What are phantom loads and why do they matter for solar sizing?
Phantom loads are the power devices draw when in standby mode — TVs, game consoles, phone chargers, cable boxes, and smart devices. A typical home has 50–100W of continuous phantom load, adding 1.2–2.4 kWh to your daily total. This is why the calculator recommends adding 15–20% to your calculated load.