It's hard to say. Depends how big the system is, and how much electricity you currently use. Here is a calculator to estimate your savings, though I will warn you that you need to know quite a few variables.
Terry, this depends on many many variables. If you installed a very large system and your normal usage is low...there is the potential to not have any electric bill at all. But those sized systems are rare...and expensive. Most folks don't calculate it based on how much they may save each year but calculate what their "payback" time frame might be.
As an example, if you are a big energy user and install a mid to large sized system this may
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cover half of your electric utility costs. Lets call this 50% savings $100 per month for some simple math. If the Solar panel system cost 25,000 and you save $100 each month, you would recover your "installation" costs in just over 20 years.
Factor in increases in electric costs over time, rebates from power companies, tax break etc. This 20 year payback may be reduced to 12-15 years.
You may save each month...but you still need to install something and those costs need to be factored in.
Terry speaking to a solar expert recently I learn that Solar thermal can save you about 30%--35% of your heating costs. Southeast solar a Hometalk member has successfully installed this in many homes and commercial building in Atlanta. You should give them a call for more details. They also claim that Solar thermal is a lot more cost effective when compared to solar panels.
Typically the number is around 30% or a bit more as YaminiM stated. This number will depend on factors such as the placement of the panels, amount of panels that can be placed, and your current electrical delivery costs.
Energy savings with solar depends on your power bill (specifically how many kWh you use each month), your available south-facing roof space (a modern 250 watt panel is roughly 18 square feet), and your budget. We have a customer in Roswell, GA who installed 10 panels and now receives a credit from the power company each month, while another customer of ours in Cumming, GA installed 22 panels and last paid $10 dollars for power. Each home is unique.
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www.dsireusa.org is a great resource to learn about available solar incentives in your area.
http://www.getsolar.com/solar-calculator/
As an example, if you are a big energy user and install a mid to large sized system this may ...»
Factor in increases in electric costs over time, rebates from power companies, tax break etc. This 20 year payback may be reduced to 12-15 years.
You may save each month...but you still need to install something and those costs need to be factored in.
www.dsireusa.org is a great resource to learn about available solar incentives in your area.