There haven't been any guidelines or formula (someone might enlighten us) for calculating how many Loules you need to protect how many watts load. Regardless, be sure the outlets you are plugging into are properly grounded or you'll be burning youtr money, literally. Newer homes have full house protection with a ground fault interupter that can react faster than a suppressor. Lightning can enter through the phone lines, coax (antenna or cable) and the power lines. Most devices using an AC adapter are going to protect the device just by the nature of the adapter.