It's "easier." I just logged into PvWatts, knowing practically nothing about solar, and I'm confused at Step 2. There's a billion variables that it wants me to fill out instead of trying to calculate them for me for optimal results.
Agreed PVWatts is more accurate, and it's what a solar installer is actually likely to use when doing a roof assessment. But to use PVWatts you need to input things like the tilt and orientation of your roof, the size of the system you want to build, the cost of power from your provider, inverter efficiency, etc. This asks for your address and your monthly electricity bill to give you a rough estimate, both of which homeowners are much more likely to know.
