Battery Drawdown

Any idea how much more?
I am sure there is an equation to work it out that someone out there will know

It depends on how efficient the inverter is.

If it was 100% efficient then it would be about the same, if it was 80% efficient it would theoretically use 20 watts of power to make your useable 16 watts. There are probably other variables that would affect it too, but you'd need an proper electronics guru for that.

It will use about the same ( except for losses mentioned already ), but it's far easier to use a 12V globe seeing as it looks like you want to use 12V as the power source.

Everyone has a fixation with inverters, but if you can avoid them, the better, as 240 V is not something to have around a camper or vehicle if not absolutely necessary ..

I cheated and used

Volts - Watts - Amps calculator

12 volts @ 16 watts = 1.33 amps

240volts @ 16 watts = 0.066 amps plus the inverter losses.

so with 20% for the loss through the inverter
240 v @ 20 watts = 0.083 amps

So all in all its down to carrying inverters and 240v items against pure 12v items

I think the inverter would draw more than 0.083 amps just to turn on.
Did you factor in the fuel usage to cart the extra weight of the inverter around or do you just carry it anyway, they are quieter than a genny that said, unless you need to run the vehicles engine to charge up the battery :)
I use2x 10 amp LED floods straight off 12v as it saves mucking about,
Cheers

Terry, I think you mean 2x 10 WATT floods, not 10 amp.
At 20 amps, you battery would be flat in a couple of hours!

Haha Yeah! you're spot on there Alan.
I think I need a better proof reader, they would put out a lot of light though.
Cheers

Don't forget you have two conversion losses.

you have losses in conversion from 12 to 240v and you have losses from 240 back to 12 volts ( or whatever voltage the led works at).

The whole point of LED is the rediculous effiency that can run at.

You may find converting from 12 to 240 and backagain will produce more losses than the LED consumes in the first place....AND a 16 watt led is a pretty bright thing to have arround the camp site.

Oh and consider too...even if the LED light you have runs direct off 240v and not thru a transformer or electronic converter...it will most likely be less efficient than a light running 12 volt native.

Led lamps and lights that run 12 volt native are soo cheap these days, why would you fiddle with double conversions and unnecessary 240V power.

cheers

LOL Terry. 120 watt LED floodlights don't bear thinking about!

OH as for exactly how much more power will be consumed...thet will depend a great deal on exactly what equipment is being used.

Some inverters will have more than 16 watts idling consumption.

cheers

Bludge: "so with 20% for the loss through the inverter 240 v @ 20 watts = 0.083 amps"

Yes, but that's the current @240V. It's still 20W (in your example) ex the 12V source.

To the O/P, as others have suggested always try and get a 12V device rather than an inverter/240V combo, for both efficiency/battery draw and SAFETY reasons.

Zippo

With all due respect.

At no stage have I suggested using an inverter, I purely used a calculator with a link for Mazdave, to put in the figures presented by the OP and Notso after Mazdave posted:
"Any idea how much more?
I am sure there is an equation to work it out that someone out there will know"

I ended with
"So all in all its down to carrying inverters and 240v items against pure 12v items"

I did not express an opinion either way so I do not understand your post to me.

Bludge, all I see is a calculation leading to an amps figure (@240V). For the O/P this info can be either useless or misleading him into thinkingthat it will be that drain on his 12v system. Maybe a tad more than the figure would have avoided that.

Thanks again Zippo,

I cannot help it if you see only what you want to see.

Did you see "12 volts @ 16 watts = 1.33 amps" ?

His question was about running 240v through an inverter and some equation to find out what it would be.
Hence
240volts @ 16 watts = 0.066 amps plus the inverter losses.
so with 20% for the loss through the inverter 240 v @ 20 watts = 0.083 amps

The calculations are just that calculations. This is what the OP asked for.

There are sufficient people on here with opinions who can fill in gaps, Bantam did so with "conversion loss and that some inverters will have more than 16 watts idling consumption".

Allan B has said basically the same thing, although he has said he wouldn't do it.

Again I offered no opinion either way. I don't see anywhere in the forum rules where I must offer an opinion, or one that suits you.

Deal with it.

No not really, I have just purchased a 120w folding solar panel to charge my batteries and am doing away with the Generator. As a result of allways having a camp set up with the generator we used the spot lights for camp light. I all ready had the inverter and thought well I can just use the existing spots through the inverter. But upon trialling it it appeared to use more power than a general 16w 12v light. The answers given basically confirms my thinking and I have ordered a 12v LED spotlight which will plug into an existing Narva outlet.