Are Solar Panels Worth the Cost?
- Jun 15, 2013 2:00 am GMT
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At a recent event on renewable energy choices, a proud homeowner showed a picture of his gleaming new rooftop PV array, and pointed out that he’d chopped down all the trees on his lot to make sure nothing got in the way of his roof.
I chuckled, having just planted some trees to save money on energy costs, which led me to ponder: tree or panel, which is greener? Is there an obvious choice?
Every ray of sunlight that doesn’t get through to a home’s exterior in the summertime is an air conditioning savings: it takes much less electricity to keep the house cool when there is no direct sun beating on it. The Arbor Day Foundation estimates that a few strategically placed deciduous trees can save 15-35% on annual cooling costs, and utilities are picking up on the idea: my trees were free as part of my local utility’s demand reduction program.
For the average US household in a single-family home, air conditioning represents 15% of all electricity expenditures. A 15-35% reduction in cooling needs means a reduction of 2.3-5.3 percent in total energy use or 300-700 kilowatt-hours (kwh) per year saved. That’s $35-$80 per year back in the homeowner’s pocket (at average US electricity rates). Using the low-end of the Arbor Day Foundation estimate (since many lots are already at least partly shaded or cannot be conveniently planted), the savings potential of tree shade across the US could be as much as 20 billion annual kWh of electricity, which don’t need to be generated.
Generating an equivalent quantity would require the installation of 2 million residential size, 5-kW solar arrays at a cost of 60 billion dollars (using figures from the Berkeley Lab Tracking The Sun 2011 installed PV cost survey). Of course, the homeowner installing the PV array will benefit from rebates, tax incentives, leasing options, save on his electric bill and might get some cash for the renewable energy credits.
For utilities, less load at peak times means better grid operation and savings on wholesale power prices to everybody’s benefit. That’s why many power companies are offering those tree-planting incentives. Solar plays a similar role in mitigating price spikes by increasing peak time supply.
The best part about trees is that they are free or heavily subsidized: rebates for shade trees are available all over the country, from SRP in Central Arizona and CPS Energy in San Antonio to Kaukana and Waunakee Wisconsin. In California, it seems like every local public utility has a tree rebate program: they are available in Annaheim, Pasadena, Roseville and Riverside. The Arbor Day Foundation has a program with several utilities to provide homeowners up to two free trees along with a cool application to find the optimal location to plant it to reduce cooling costs. The group just finished its spring shipments, which went from March through May, but the next round starts in October for fall tree planting season.
For those us with trees on our lots: don’t chop them down, shade is good! If you have the space to plant shade trees, ponder the tree to panel tradeoff – and where available, consider investing in a community solar project instead to offset your remaining air conditioning load!
…The only problem with trees is that they take time to grow, so plant sooner rather than later.