Idle or Standby Current or No Load Power Drain
is an important figure, if you'll leave the inverter turned on (idling), so that it automatically delivers full power when an appliance is turned on. This can equal nearly 20 watts of 12-volt power in some brands. (20W at 12V = 1.7Amps). Quality inverters draw only a fraction of an amp (as little as a tenth, or much less, of an amp) at idle.
should exceed 90% overall. It should not vary much from partial to full loads. Beware of inverters that advertise 90+% overall efficiency but may drop to less than 50% at some load levels.
Other specifications, such as output voltage
and frequency regulation
should also be compared, but will be similar in high-quality inverters. Note that top quality inverters will regulate voltage, for example, to within 2% of the rated 120VAC. This is better than your power company, which usually regulates voltage to only Ī5%!