The system includes 6 panels on our garage roof, 8 huge deep cycle batteries, an inverter (to covert the DC energy to AC), a monitor (to keep track of the energy generated, used, and stored in the batteries), an electrical outlet inside the house, two electrical outlets in the garage, a small fan to vent the battery compartment, and some emergency lighting.
The panels are rated to produce 1.7 KWh each hour the sun is shining and in the right position in the sky (A KW is 1000 watts, and a KWh is 1000 watts for an hour. For example, 10 100 watts light bulbs would use up a KWh in an hour. A slow cooker is rated at 300 watts, so that would use 1.5 KWh if you cooked with it for 5 hours. Note: All the math makes solar power a lot more fun.). We’re hoping the solar panels give us 15 KWh on a sunny summer day and perhaps 8 KWh on a sunny winter day. Our goal is to have available at least 5 KWh per day year round, even if we have three cloudy days in a row. (The batteries provide the power when the sun isn’t shining. The “Dummy” books suggested we store enough power for 4 cloudy days, but the solar guys talked me down to about 3. I still don’t know exactly how much energy the batteries can store and produce, because getting an straight answer about batteries isn’t easy.)
Although we wanted the solar power primarily for emergencies, we decided to hook up a refrigerator and a freezer to the system so that we didn’t waste all the electricity we could produce while we wait for the power to go out. A few weeks ago we noticed RC Willey had a sale on all its Energy Star appliances (Energy Star is a government designation for energy efficient appliances), so we went looking for a refrigerator and a freezer for the garage that would work well with the solar system.
We weren’t too concerned about prices, but we did look closely at how many KWh per year each appliance would need. We found a fridge that used only 400 KWh and a freezer that used 550 KWh. Unfortunately for the environment, none of the Energy Star freezers were frost-free, so Marieta vetoed them all. We ended up buying a freezer that needed 800 KWh. We found that the efficient appliances were relatively inexpensive (and came with government rebates), but they lacked any fancy options like an ice maker or filtered water.
If we assume we will have 1,825 KWh of power to use in a year, we should have more than enough to provide 1,200 KWh for the appliances. We’ll see. We did put the appliances are on a special plug, so that regular power will take over if the batteries run out of juice.
I’m still not sure of the final price of the solar power system, but it will be about $20,000. If we generate and use 5 KWh per day, we will save 50 cents each day on our power bill. If this were an investment (and not just a project to keep me out of trouble), that’s a return of a little less than 1%. With the government rebates (by the way, I would like to thank those of you who pay taxes for contributing to our solar power system), the cost could be cut in half and the return could be as high as 2%. I will let you know the actual amounts once we know them.
In my next message, I hope to explain more about the batteries. I thought it would be a simple calculation to multiply the amount of energy one battery could hold by the number of batteries in the system to find out the total stored power in the batteries, but it’s not that simple. I wish I had paid more attention in my chemistry and physics classes.