On my boat I have two fixed 12v cigarette lighter outlets near the power board. I also have a smallish 800w inverter. The only thing I use the inverter for is to power my cryovac machine as well as charge phones, tablets etc and a small 12v flat screen TV

I have always believed that using an inverter to drop the power to 12v for charging and small appliances draws more amps than if they were charged or run directly from a 12v outlet due to the stepping down process.

I was recently told this is incorrect.

Can anyone who is knowledgeable on this subject tell me what is right.

Thanks,

Rick.

I can give you precise answer, but you must ask very specific question.
There are many ways how to look at the subject
the main reason for confusions.
I give you a few examples for you question.
a/
the most devices these days are charge up from 5 volts USB plug.
old style converters from12V down to 5V the differece is 7volts
what happen with 7 volts. times current..turns to HEAT
new style, comes as a accessorie, less heat ..more efficient
b/
my iPad charging 10 hours from 12 volts, 3 hours from 240 power pack
that's problem typical for most devices
whitch one you prefer?

c/
inventors, new style very good but idle current ( stand by current) is very high
just to plug in 12V you loosing 0.8 A
for cryovac machine the current is negligible,
for small appliances, I personally use much smaller inverter
300 watts inverter ...idle .5A still a lot, considering charging time

The most current appliances use LiPo or similar batterie, means
every device has build in another inverter either step down or up.