We recently had a 3.57 kW solar energy system installed on the south-facing roof of our house, but I was a little concerned about it because after the system was designed and paid for my wife decided to get a Ford C-Max Energi plug-in hybrid as a company car. The C-Max Energi uses about 8 kWh of electricity to recharge its battery pack via standard outlet when it's depleted and we hadn't planned on that when the system was designed.
Well, we finally got our first bill after energy production started and we owe a grand total of $1.78 for mandatory service fees. We ended up producing 109 kWh more than we used for the month. We had been cutting back on electric use lately by changing everything to CFLs, unplugging appliances that weren't being used, charging laptops and phones at work instead of at home, etc, but I was really pleasantly surprised at how little energy we used compared to what we produced. Hope we can keep this up!