Inverter Size Calculator - Recommended Inverter Wattage
Calculate total appliance load and recommended inverter size, including a safety margin for startup surge.
Appliances
#1
#2
#3
Typically 20-25% to cover startup surge and efficiency loss
Recommended Inverter Size
563 W
Total load: 450 WHow to Size an Inverter for Your Appliances
List every appliance you plan to run at the same time along with its running wattage, then add a safety margin to cover startup surges and inverter efficiency losses. The result is the minimum inverter capacity (in watts / VA) recommended for that combined load.
Example
A refrigerator (200W), LED lights (100W), and a TV (150W) add up to a 450W total load. With a 25% safety margin, the recommended inverter size is 450 × 1.25 = 562.5W — round up to a common inverter size like 600W or 800VA.
Common Use Cases
- Sizing a solar power system's inverter for expected household loads.
- Choosing a home backup UPS or inverter for essential appliances during an outage.
- Planning power needs for an off-grid cabin or RV setup.
FAQs
Why add a safety margin on top of the running wattage?
Motors and compressors (like those in refrigerators, pumps, and air conditioners) draw a surge of current well above their steady running wattage when they first start up. The safety margin buffers for that startup surge plus normal inverter efficiency losses, so the inverter doesn't get overwhelmed the moment a motor-driven appliance kicks on.
What's the difference between watts and VA?
For purely resistive loads (like incandescent lights or heaters), watts and volt-amps (VA) are roughly equal. Inductive loads with motors have a power factor below 1, meaning their VA requirement is higher than their wattage — treat the wattage total here as a starting point and lean toward a larger margin for motor-heavy loads.
Should I add up every appliance in the house?
No — only include appliances you realistically expect to run at the same time. Very few households run every appliance simultaneously, so sizing for your actual expected simultaneous load (not the sum of everything you own) gives a more realistic and cost-effective inverter size.