How many hours will a 215 Watt consuming plasma tv last on 800 VA inverter?

The rating mentioned for the inverter refers to current /voltage capability. (It approximates to a power rating of up to 800 Watts although power and VA are slightly different measurements). The television uses 215 Watts which is also a power rating. Therefore, the television will run continually on the inverter without overloading it.

The time limit for operation is the battery that is supplying the inverter with energy. As the battery is not specified the operational time can't be calculated. However, if we take an example of a 12 Volt battery with a capacity of 70 Amp hours (a size that may well be found in a car), the amount of energy stored in the battery should operate the television for a theoretical time of just less than four hours. In reality, the battery will not be capable of delivering all of the energy it stores so some time is likely to be lost. The television power rating is often quoted as the maximum power draw and it will probably draw less power than 215W. This means that the time may be rather longer than 4 hours.

There are a lot of factors such as battery efficiency, power draw, temperature, inverter efficiency and brightness setting of the television that all have an effect on the operation time so the only real method is to hook it up and try it.

If the power source is a lead acid battery then make sure the battery is not left discharged for long periods. Leaving it discharged will adversely affect the life span of the battery so get it back on a charger as soon as possible.