The cost to run your TV for an hour will depend on the wattage of your TV. But lets take my LED TV for example, my led TV uses 85 Watts so if I watched 8 hours of TV per day it would use 680 watts of electricity for 8 hours which would cost me around 8 cents per day.
8 cents per day times 30 days would be $2.40 cents per month to watch my TV for 8 hours per day.
Now that's for my TV and yours if it uses 85 watts but you'll have to adjust these figures to the wattage of your TV and what a KWH costs you on your electric bill.
In my case I pay 10 cents per KWH and the TV would use just under a KWH "1,000 watts" for 8 hours of run time.