Let’s admit it, utility electricity is still downright cheap compared to renewables, even when heavily subsidized. So to really make it a cost effective solution, you need to look at several factors.
The procedure you should go through to decide if a solar electric system is cost effective for you is the following:
- Look at your utility bill to find out how much energy you use, and how much it costs you
- Invest money in energy conservation to get your electric bill as low as possible; every dollar you spend on conservation will save $3 to $5 on the cost of a PV system
- Find out the energy resources at your location – look at the DOE map below
- Check the federal, state, local, and utility incentives and laws that may be available to you using the DSIRE website
- See how much money you’d have to invest in PV to make a difference in your utility bill
- Then make a decision!
Solar Radiation Map (source Dept of Energy) to help you find out your energy resources.
Figure out what your insolation (Incident Solar Radiations) number is from the map. For me, it’s 2.7 for Northern California. The number represents kilowatt-hours per square meter per day, often called in the PV industry “full sun-hours” per day. Note: The map above shows the worst-case scenario in December, which is what you would want to plan for if you wanted to power your home entirely from the sun all year.
Now let’s say I’ve installed a 1-kilowatt (1,000 watt) PV array. So, 2.7 hours × 1,000 watts = 2.7 kilowatt-hours (kwh) per day, on average, from your array. Each residential kwh from the utility costs about 11 cents, on average, in the U.S. I’ll be making a little less than 30 cents’ worth of energy every day!
That’s some math. How do you do your cost analysis? In any case make sure to check the DSIRE website for current federal, local and utility incentives.