For calculating savings from solar PV systems there is no universal method. Your savings will depend on your location (i.e., climate), incentives, and net metering laws for your state, system rating (in kWh), array type, local electricity costs, your specific energy usage, and more. A solar PV system in San Francisco, CA will save its owner, on average, twice as much per year as the same solar array in Grand Rapids, MI.

Fortunately for those of us whose minds don’t work like scientific calculators, several solar companies and organizations have created programs to help do the math for us. If you know the details of your prospective solar array (fixed or tracking, panel tilt, capacity, etc.) and where you live, then you can, in just seconds, receive an estimated savings amount. This program, at pvwatts.org, breaks it down by month and is very user-friendly.

Here are some figures for a solar PV array in San Francisco that is fixed tilt (37.6°), facing due south, and using the state average as cost of electricity:

• 2.o kW=$361.50/year (Avg. $30/month)
• 3.0 kW=$542.25/year (Avg. $45/month)
• 4.0 kW=$722.88/year (Avg. $60/month)
• 5.0 kW=$903.62/year (Avg. $75/month)

You can see a pattern here as savings increase by about 15 dollars per month for each extra kW in the system’s DC power rating (system size). It is important to note that this program factors in location, energy costs, and system details. To calculate a payback rate for your photovoltaic system you will need to figure the net cost of installation (the gross cost minus rebates, incentives, etc.).

Sticking with San Francisco as an example, using the California Solar Initiative (CSI) Incentive calculator, a 2.0 kW system will get about a $3,500 rebate. Even in California the rebate amount can vary significantly based on location and expected output of the system.

Also, California is a very progressive state in terms of solar energy promotion. A different state may well have a smaller incentive program at this time. Yet nearly every state has incentives of some kind and states like California and New Jersey are setting the bar. You should feel confident that incentives will continue to grow at least until solar is a much more significant source of energy in the United States. To learn more about incentives in your state, look here.

The biggest saving of them all, and the heart of the solar movement, is a green earth. Many will argue that solar does not save money because of the large up-front costs (hence the push for state and federal incentives and rebates). In some cases they would be quite right (although that seems destined to change as technologies advance and prices fall), yet solar savings is not all about the bottom dollar. It is also about curbing emissions and global warming. It is about fresher air and energy independence. The comprehensive beauty of the recent solar explosion is that now you can save your money while saving your environment at the same time. Still, at this time, a solar home PV system can be a daunting investment. But sooner or later, and hopefully sooner, it will be a given.

Posted on May 26th in Solar Information by Dan.