Inverter Draw When There Is No Load ?

[SvenG]

Do the small 12v inverters draw full power continuously, even if there isn't a load ?

I'm assuming that they are 80-90% efficient but wonder how that varies with the load. Will a 300w inverter draw 300w when powering a 10w toothbrush charger, for example ?

Thanks,

[bobfnbw]

No. It will draw the 10w plus the extra the inverter needs to do its stuff.
It will usuallly draw a small amount of current when not being used, but a small amount. Every inverter is different in the amount it will need to convert dc power to ac power so check the specs on it. How efficent it is.

[GordMay]

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.

Efficiency 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 ±5%!