This summer marked a permanent reduction in our power bills, with the joyful completion of a 7.6 kW solar array!  I’ve wanted to invest in solar for years, but shopping for a reasonably priced yet competent installer always ended up on the back burner.  Despite the desire to do good by the environment and participate in an emerging distributed grid of clean energy, the costs are quite substantial, and is has proven quite difficult to determine what the payback on such an investment would be.  Between state rebates, federal and state tax credits, depreciation, choices of flat or time-of-use metering, a stack of rates based on consumption, which change seasonally and will probably increase in the future, figuring out the payback required too many assumptions to give me confidence in the resulting numbers.

My enthusiasm to figure this all out was renewed on a visit to the Horton Iris Farm, where they have a new 3+kW roof-top system.  The installer, Coy Ware of Coy Solar, has been a friend of the Hortons for a long time, and has a long history of general contracting, electronics, and eco-friendly technologies, so it didn’t take long for us to analyze our usage, figure out the parameters of the system, and get underway.  We calculated the payback at somewhere between 4.5 and 9 years - a pretty wide range but that was the best we could do.  At either end, I was willing to invest though.  Coy devised clever ways to move materials and equipment around the site since it isn’t very accessible by machinery.  It took about 6 weeks of steady and at times heavy manual labor to construct and install the system on the hillside below our pool, especially to Coy’s standards of excellence!

We switched it on about 6 weeks ago.  The system is a grid-tie, meaning that there are no batteries or other storage mechanism.  Excess power is pumped back into the grid, making the meter spin backwards - what a sight!

A new digital meter courtesy of the power company, and the System Lifetime readout on the solar has helped me keep track of how much I’ve saved - not a trivial proposition given the rate schedule involving baseline rates and increasingly expensive rates the higher over the baseline you go (the exact opposite of volume discounts).  I put together a rather complex spreadsheet simulating a virtual power bill and the resulting savings of $519.75 for the first 47 days.  Not factoring in the tax savings, a straight-line estimate at that rate puts the payback at around 8 years.  I hope to see that period shorten as rates rise (as they no doubt will within the timeframe), and the actual tax savings can be measured more accurately.  Over the life of the system, it should pay for itself many times over.

And the air is just a little clearer than it otherwise would have been. Those benefits will accrue for years as well.