By Jon Fisher, The Nature Conservancy
We all want to decrease our energy use, both for the sake of our wallets and the benefit of the planet. But is putting solar panels on our home rooftops the best way to do that?
Residential solar systems (especially photovoltaic or “PV” systems) are substantially less efficient than their commercial counterparts. One estimate (admittedly controversial) from UC Berkeley professor Severin Borenstein says that residential PV systems cost roughly twice as much as their commercial counterparts (40 cents/kWh vs 20 cents/kWh)1.
Commercial systems have many advantages over residential: they are typically developed in locations with lots of sun, they can take advantage of innovative technologies that don’t work at small scales, they can utilize larger storage cells, and many other reasons.
Which brings us back to the question of why so many people love the idea of putting solar panels on their roofs. In talking to friends and co-workers who have solar panels, there seem to be two common reasons: the appeal of being energy independent and an “every little bit counts” desire to do their part to help. Installing solar panels on your own home is a more readily achievable goal than successfully lobbying to change the way we subsidize different kinds of power plants.
The good news is that there’s an often overlooked form of residential solar power that is almost always far more efficient than photovoltaics. Solar Water Heating Systems (SWHS) are typically much cheaper than PV systems, and focus on using heat from the sun to produce hot water (which is much simpler than converting sunlight to electricity).
While PV systems may take decades to pay for themselves (although this varies considerably state by state due to considerable variation in both subsidies and how much sun is available), solar water heaters can pay for themselves much more quickly. There is an excellent article on payback times in Home Power magazine (note that it doesn’t include subsidies, which vary substantially by state and city).
When subsidies are included, I found out that for my condo in Arlington, VA, a SWHS would pay for itself in 2-4 years as opposed to about 30 years for a PV system. Since SWHS are much more efficient than PV systems (in electrical energy equivalent per area), you could even install a solar water heater and still have room for some PV panels if you wanted them and the local conditions are favorable.
While I am excited about the evolving technology behind commercial solar power plants, using the sun to heat water in your home is a no-brainer if you can afford to pay for the initial cost while gas savings pay you back. As the cost of natural gas rises (and drilling puts more pressure on natural areas) this will likely become even more appealing.
Those still interested in residential PV systems may be interested in a cost calculator, and if you really want to understand the technology the Department of Energy has a very detailed handbook available which covers both PV and SWHS. Installing a PV system in your home is still a great idea if you’ve already taken care of easier green improvements (including a SWHS) and still want to do more, especially in states with lots of sun and good subsidies.
If you’re on the fence, an energy audit is an excellent way to find out what the easiest and most effective changes you can make around your home to ensure that you can put your conservation dollars to the most good.
1. Note that Dr. Borensteinís estimates are controversial; read one of his major analyses of solar’s costs and benefits, two critiques of his work (by Bill Powers and Tom Beach/Patrick McGuire), and his response to those critiques.
Jon Fisher is a data management specialist for The Nature Conservancy, the world’s leading conservation organization. He has studied forestry, environmental biology, stream ecology, environmental engineering and how technology and spatial analysis can improve wildlife management at airports. He also loves to cook delicious vegan food. Opinions expressed here are the personal opinions of the author and do not necessarily reflect the views of The Nature Conservancy.
(Image: President Nasheed of the Maldives installs solar panels on his home in Male, Maldives. Source: 350.org via a Creative Commons license.)