12 volt vs inverted 120 volt

I'd like to know about how much more power will be used to power a TV that uses 50 watts from a 12 v. battery through an inverter compared to wiring it directly to the 12 v. battery. Assume the TV has the 12/120 v. option. Essentially--what's the loss due to the inverter? Thanks.

does the tv not have a label that tells you the power consumption??

This is a hypothetical. I don't actually have the TV yet. I need to replace the 13" analog TV in my motor home by Feb. 2009 with a digital one. I'm trying to decide whether to get a 17-19" LCD (a great size but hard to find in 12 v. at a reasonable price) or a smaller one that uses 12v. directly. One of the primary factors is power consumption when I'm camped somewhere with no electrical hookup.
The 13" I have now allows me to watch a couple hours each evening (along with other conservative power use) for about 6 days before having to charge the house batteries.
I just wondering how much loss there is with the same (hypothetical) TV under the two voltages.
Thanks,
Keith

Depending on the quality and the output waveform of the inverter, you could be looking as low as 50% efficiency, but most modified sine wave outputs will probably land you closer to 85 to 90%. Pure sine wave inverters are basically Class A/B power amplifiers, and will never exceed 66%.

I'd bet money that MANY 17 to 19 inch LCD monitors or TVs power bricks are 12 volt outputs, anyway. Check into that before you decide on a final purchase!

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Regarding the power bricks, I've been told that one could just cut the brick from the 120v power cord and wire it for a 12v outlet. The problem with that is that not a single smaller TV (19") I've been able to look at has the power brick. Only the big ones do, like 42" & bigger. On the 19" ones, the power cord goes directly from the wall socket into the TV chassis. They may run on 12v, but the inverter is internal.
Keith