Most people don’t have enough space on their roof to offset 100% of their electricity needs. You can still offset a portion of your electricity bill with solar. A solar system on a typical house will produce about 30-60% of your electric needs (assuming an average consumption of 850kwh/month). But that percentage depends on how much electricity you use. Your installer will estimate how much solar will fit on your roof. They will also estimate the amount of electricity your system will produce each year. These projections are very accurate, based on several decades of testing by the U.S. Department of Energy. You can use the website, PV Watts, to estimate how much solar you could put on your roof. Then, you can compare the system’s estimated annual electricity production to the amount of electricity you used last year. This will tell you what percentage of your electric bill you could offset with solar. Click here for a tutorial of PV Watts.