Wattage of heaters depends on the specific heater. I think they range between 200 and 1500 watts I think.
Here's a 4 stroke clone at Costco:
http://www.expeditionportal.com/forum/showthread.php?t=30236&highlight=costco+generator

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13