I have to speak up in support of the author in "Let the Sunshine In" (4/20/2012). Marshall Alwin's letter ("Cloudy Forecast," 4/27/2012) reported incorrectly that "manufacturers suggest an 18-to-20-year life on photovoltaic panels," and that the residential customers would be "looking at an 18-year payback." First, 25-year warranties are standard in this field now. Some PV manufacturers do state a 90% rating after 20 years, but all that I've seen guarantee at least an 80% rating up to 25 years. Many PV "panels" from the 1970s and 1980s are still producing electricity today, over 30 years later. Chances are good that today's PV modules will last 40 to 50 years, and degrade at only about 0.5 % per year.
The letter writer is correct in assuming a residential "payback" is longer than for a business, since the business can take the depreciation as a deduction on their taxes. But, at today's prices (and considering utility rate hikes), at $5 a watt, a residential customer could see cost recovery in 14 years, with an internal rate of return hovering around 5.8% over 25 years.
Kurt Reinhold, Solar Connections LLC
Marshall Alwin is incorrect when he states that photovoltaic (solar electric) "panel manufacturers suggest an 18-to-20-year life on photovoltaic panels." In fact, module manufacturers, both domestic and foreign, warrant their modules against power output loss for a standard period of 25 years and, in some cases, 30. Documented cases exist in which photovoltaic modules are still producing 95+% of their rated output power approaching year 35.
Mike Joyce
The interesting thing about "Cloudy Forecast" is that the writer correctly notes that the systems will be producing efficiently at least 80% of its day-one production level under the warranty. The solar panel doesn't just stop working on the 18th year, which means the economics of solar get better with each day the system works after that the 25-year warranty expires, even if not at full production capacity. In the unlikely situation a solar panel did suddenly stop working on its 25th birthday; you would expect to have paid about $0.15 for every kWh produced during its 25-year lifetime. If the solar panel suddenly stopped working on its 30th birthday, you would expect to have paid about $0.10 for every kWh produced during its 30-year lifetime.
Compare this to the $.13-$.155 per kWH homeowners pay today and the $.21 per kWh they can expect to pay if electricity prices rise at the same historical rate.
The economics of solar are very particular depending on each homeowner's situation and require a long-range investment planning approach. But implying that solar doesn't make economic sense for the mainstream by overlooking basic facts continues to hold solar back.
Bryant Moroder, MadiSUN Solar Program
With the current loss of Focus on Energy rebates, it is true that the payback period is out around 19 years. But last year, even the base level of Focus rebates dropped the payback period to 17 years with an ROI of 5.5%. And with last year's energy-efficiency bonus rebate, the payback came down to only 17 years with a 6% ROI. And Focus is promising to announce a new rebate program soon, though expected to be at a lower rate.
Solar is indeed a "patient money" investment, but it is not hard to see why people have been willing to accept these returns and get the additional benefit of reducing their CO2 footprint and their mercury emissions.
Larry Walker, Walker Energy Systems LLC
