How the check works
Two tests must both pass. First, running load — the appliance plus anything already on — must stay under the inverter's continuous rating. Second, the startup surge: motor appliances briefly pull about three times their running watts, and the inverter must tolerate that spike (good inverters handle roughly twice their rating for a moment). A system can pass the first test and still fail the second.
Why "running watts" alone misleads
A 1 HP water pump runs at 750 W but can spike past 2000 W for the instant it starts. Sizing on the 750 W figure alone is how undersized inverters end up tripping every time the pump kicks in. This tool always adds the surge for motor loads.
Getting the numbers right
Running watts are usually printed on the appliance label or manual. If you are unsure whether something has a motor, the rule of thumb: anything that cools, pumps, or spins a heavy load (ACs, fridges, freezers, pumps, washing machines) surges on start; pure heat and electronics (irons, microwaves, TVs, lights) do not.
Will a 1.5 ton AC run on a 5 kW system?
Yes comfortably — a 1.5-ton inverter AC draws about 1200 W running, well within 5 kW even with fans and lights on. The tighter question is always the inverter's surge rating for the compressor start, not the running watts.
Why does startup matter more than running watts?
Motors and compressors draw two to three times their running power for a fraction of a second when they start. A system that carries the running load can still trip on that surge if the inverter's surge rating is too low.
What does a 'tight' result mean?
The appliance runs, but you are using more than 85% of the inverter continuously — leaving little room for anything else to switch on. It works, but a slightly larger inverter would be more comfortable.