Does the TV itself have a power usage indicated on it? It's possible it may require less than the adapter it came with is able to produce. They might use the same adapter for a wide range of television sets. If you have an appropriate DC ammeter, you could even measure its actual usage with a little bit of effort.
I think the biggest power consumer in a modern TV is the backlight for the screen, and its power consumption would somewhat vary with how bright you have it set for.