How to Size Your Inverter
Size continuous and surge watts for DIY off-grid and shop inverters, with a garage example and links to protection gear. All items listed include affiliate links. Use of links or discount codes will pay a small commission to Mike’s Solar Garage LLC at completely no cost to you.
The plain math
1) Add continuous watts of loads that may run together. 2) Note the worst surge (motors, compressors). 3) Pick an inverter continuous rating above the continuous total with headroom. 4) Confirm surge rating covers the motors — or add soft starts (tools & accessories).
Example: Shop lights/computers 800W + fridge 200W + occasional compressor that soft-starts at 2000W surge. A 6000W-class unit can work for light shops; big split-phase tool walls often land in the 12kW-class DIY lane (EG4 12000XP territory). See XP vs Solis.
Next
Continuous vs surge watts
Continuous watts must cover everything you expect to run at once. Surge watts cover the short spike when motors start. If surge is the problem, a soft starter often helps more than buying a much larger inverter. Pair this page with protect an EG4 12000XP and tools & accessories.
Split-phase shops and homes
Many US garages and homes need 120/240V. Confirm the inverter supports your panel plan before you buy. Off-grid shop builders often land on the EG4 12000XP lane; meter-first homes often look at hybrid—compare 12000XP vs Solis.
Worked garage example
Table saw 1800W + dust collector 1200W + lights 200W = 3200W running. Compressor surge may briefly hit much higher. Size continuous above 3200W with margin, then either soft-start the compressor or confirm surge headroom. Battery bank kWh is separate—see size your battery bank. Shop context: solar power for garage and shop.