You really don't need much if you can recharge the battery daily. We have a 26" TV and a DirecTV DVR. Together they pull less than 100w. We run it off a deep cycle battery and a 400w inverter that I got from Newegg.com or maybe Amazon. I think the inverter cost $30 on sale. The battery is a deep cycle battery from Sam's Club. I don't remember what size but it's one of the larger ones but it's way more than we need to run the TV. We've run it for 4 or 5 hours with no problems. The battery will fully recharge in a couple hours using a Harbor Freight charger, the one they often have 'on sale' for $30.
2008 Ford F250 Super Duty, Lariat, 6.4l PSD, Super Cab. Long Bed
2006 Jayco Jay Flight 27.5 RLS Fifth Wheel