If your TV is a CRT type instead of LCD it may require a pretty good surge of power when first turned on in order to energize the degaussing coil so I'd go for a 400 watt inverter or better. A 200 watt inverter would do if the TV is LCD. Also there is a chance for RF interference on a CRT type TV but not likely on an LCD.
With a modern LCD TV, I would use a 600 watt-rated inverter connected directly to the house battery with wires and connectors provided and run an extension cord to the TV. Some LCD TV's can run on 12 volts DC directly from the house battery without using an inverter.