There's something completely wrong with the original scenario in this thread. The Pacific Northwest has the cheapest power in the U.S. Here's a .pdf of
Seattle's rates. They have many different rate schedules, so I picked the generic city schedule.
Summer schedule: First 10 kWh /day: 4.75 cents per kWh. After that you get punished. 10.8 cents/kWh.
Winter schedule: Only change is the first 16 kWh/day is 4.75 cents. So you can use more in the winter before the rates bump up.
Lots of people would kill for rates like that.
So let's do some backwards math.
15 cents/day meter charge. $4.50/month. Round it off to $5 and subtract from $500/month.
$495/month divided by 30 days = $16.5/day. Let's round it back to $16 for the sake of argument. How much power would you have to use to spend that much in Seattle? We'll use the winter rates. Those first 16kWh/day only cost 76 cents. After that you're at the 10.8 cent rate.
Subtract the 76 cents from $16. $15.24 is left. $15.24 divided by 10.8 cents/kWh = 141 kW!!?? Wait, that can't be right.
Someone correct me if I'm wrong, but it looks like you'd have to use roughly 150kWh per day to ring up a $500 monthly power bill in the City of Seattle.
Now let's look at a map of U.S. solar
insolation. See that blue pocket in the upper left? The area with crappy solar potential? Yeah, that's Seattle. The OP claims that his friend, the guy who uses 150kWh per day, hooked up some panels on a cloudy day and the meter went backwards.
That's possible. If his friend went to the breaker panel and turned everything off. But to claim that a few dozen panels in the cloudy Pacific Northwest is gonna offset a $500/month Pacific Northwest power bill is just pure bullshit. You gotta want it bad to install PV in Western Washington precisely because of the double-whammy. Solar potential is really low, and grid power is really cheap.
Anyone who knows anything about solar knows that it would take a lot of PV panels in Arizona to offset that level of consumption. To do it in Seattle you'd need a warehouse roof.