I recently did an ROI on a 2.7 kilowatt grid-tied home roof-top photovoltaic (solar) energy system for our new house. Grid-tied means that any excess energy produced by the system is fed into the Austin Energy grid. As long as you produce less energy in a given day than you use, which is (overwhelmingly) usually the case, Austin Energy reduces your energy usage on a one-to-one basis. This means they are paying retail for your solar produced energy. Each power company has its own rules concerning this, so it may be different at your house. In the unlikely event that you produce more energy than you use in a single day, AE will credit you at wholesale rates, about 1/3 of retail.Rebates and Bottom Lines
This is an add-on system; structurally integrated systems are significantly more expensive. The total cost is about $20K. There is a 30% federal tax credit available and other incentives, including an amazing $5/watt that covers up to 80% of the invoiced cost, from Austin Energy. Even with all of those subsidies, net cost is optimistically about $3K. The maximum output per year at current electricity cost is optimistically about $350, according to Austin Energy solar expert Mark Kapner. My spreadsheet said that it would pay for itself in about 8 ½ years. Mark says that field data, including maintenance, suggest the real number is typically between 12 and 17 years.
Solar-less for Now
An increase in electricity costs would decrease the payback period. Since sunlight is free, system price is the main driver. The primary issue is the fact that solar energy is the least dense energy source available (much less dense but more reliable than wind), and solar panels currently convert only about 11% of the solar energy into electricity. We have decided that it would be prudent to wait for either a dramatic reduction in system cost or a similar increase in electricity cost (possibly driven by solar subsidies) before installing a photovoltaic system.
Charles
I agree, the solar panels don’t quite work yet. I was hoping to use them on our project, but the expense vs cost savings was too far apart.
ReplyDeleteSomeone in this field was was telling me that battery/storage needs to be improved for solar collection to work. We need some breakthroughs in technology.
Also, it would be nice to see AC systems improved. A lot of wasted energy goes into the discharge of heat into hot air. If it could discharge into water or the ground that would be much more efficient. But doing that is still too expensive.
For stand-alone solar systems that are not tied to an existing power grid, batteries are definitely an issue. The system I priced is a grid-tied unit that requires no batteries;the grid serves as a storage device. For this type system we need breakthroughs in efficiency versus cost.
ReplyDeleteThere are systems available that use wells as a heat exchanger. They hold some promise, especially in areas where well drilling is inexpensive, but, as you said, the payback is not currently compelling.
I agree that decreasing usage is still the most cost effective approach.
Solar energy is the best natural resource that we have this time even more that fuel is too expensive. In fact i want to approach costa rica investment opportunities and look all the alternative this country can have because it climate. We must to find the way to save our planet and to use solar energy could be the first step.
ReplyDelete