There are two primary inverter categories: Modified (also called Quasi or Square Wave) and Pure Sine Wave. Modified types cost less but can introduce hidden expense, as some equipment performs poorly or fails prematurely when powered by them. Pure Sine Wave inverters work reliably with all electrical loads and provide superior power efficiency.
Types of AC load
Resistive loads operate equally well on both inverter types with consistent power draw. A standard 500-watt lamp, for example, draws exactly 500 watts.
Inductive loads contain wire coils, solenoids or transformers, found in motors, refrigerators and pumps. Both inverter types support them, but Pure Sine Wave performs significantly better. These loads can surge to up to ten times more power at start-up, so a 200-watt operating load might require 2,000 watts initially.
Capacitive loads produce sudden current surges during start-up and operation. Modern power tool chargers commonly feature capacitive loads. A case where a 1000-watt inverter will not power a 500-watt charger typically results from a modified inverter overloading due to current spikes.
Recommendation
Where budget permits, select a Pure Sine Wave inverter and allocate more power capacity than you expect to need.