Last night my wife and I spent approximately $12 plus an hour of time to make 24 cupcakes. I couldn’t help but wonder how much it would have cost just to buy 24 cupcakes. This question frequently comes to mind when I think about DIY home repair, or DIY furniture making (something I expect to take on this weekend). Considering cost, time and quality, is it really better to do it myself? Hard to say.
When you get to solar, however, the answer looks a little more obvious. Should I generate my own solar energy or let the professionals do it? Intuitively I always knew residential solar had to be less efficient than commercial arrays, but nevertheless I was shocked when I saw these actual figures in a recent NREL paper.
Installed Costs ($/watt)
$4.00 small commercial
$3.00 large commercial/industrial
Residential solar – nearly twice as expensive per watt! The economist in me cringes at all the waste implied by that $2.50 spread (wasted materials, energy and of course labor). There might be an argument based on local sustainability for mid-sized arrays such as solar gardens or solar on top of the local Walmart, but not for solar on my roof (actually I don’t have my own roof, but I’m speaking theoretically here).
Whether I look at solar as an investment, or as a way to help the environment, scattering it here and there on people’s rooftops just doesn’t seem to make sense.
As a note, full cradle to grave efficiency could be even worse if the calculations didn’t include variance in operating efficiencies caused by seasonal cleaning and azimuth adjustments (both I expect are far less likely on residential systems). These figures only appeared in a supporting table of the report, so I don’t know the study methodology, but either way, the difference is clearly huge.