I installed the first part of my solar power system in the fall of 2009 and immediately my power bills dropped considerably.
The chart below shows the energy flows for my property over the last several years:
Take a moment to study this chart and look at how everything interacts. The yellow line shows how much surplus energy I export back into the grid on a monthly basis from the solar array. Clearly, in the summer I am exporting a lot more and this more than offsets my net energy for the month. Whenever the green net energy line goes below zero, that is when I have a credit.
This chart shows my actual bottom line monthly electric bill:
years I have scaled up my solar power system and now my electric bills
flatline in the summer, bottoming out to the minimum connection fee. This year I had a surplus from May through October and the utility gave me a credit that carried forward until it was used up. This electric bill covers both my house, workshop, and the electricity used to charge my Chevy Volt. So, not only am I not paying for utility energy for months at a time, I am also driving up to 37 miles a day for free on solar power.
During the summer months the energy I am exporting into the grid reduces the load on the power lines feeding my immediate neighborhood. As neighborhoods grow, the utility often needs to upgrade the infrastructure in order to deliver power to outlying areas. If new housing developments were all to incorporate solar roofs on their houses, this would reduce the cost of deploying and maintaining power lines to those areas. You would think that utility companies would appreciate this benefit, but in reality they are pushing back against it because of the lost revenue. Some utilities are even trying to punish customers with solar power with a surcharge to cover maintenance costs on their power lines.
My solar power system, like most systems installed in the last 5 to 6 years is utility inter-tied. This means that there is no battery bank and surplus energy is returned to the grid rather than being stored in batteries. However, battery technology is now reaching the point where it is beginning to become relatively affordable to pull the plug on the utility altogether and simply store that surplus energy in a battery for use overnight and on cloudy days etc. This is referred to as "grid defection". Renewable energy pundits are suggesting that entire communities could pull the plug in the future and that utility companies will need to figure out a new business model.