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Green Building Myth #5: Adding Solar is the Best Way to Green a Home

The last several weeks I've written about common myths of green building: that it has to cost more to build green, that green building is mostly about materials, that green products don't work as well as conventional products, and that it's hard to find green products. This week I'll cover the myth that adding solar panels is the best way to green a home.

Without question, solar-electric (photovoltaic, PV) or solar water heating panels are the most visible green feature of many environmentally responsible homes. Either roof-mounted or installed on separate racks, those solar panels are in full view, they're unusual enough to be noteworthy, and they convey--almost shout--a commitment to the environment. And rest assured, I'm a huge fan of both photovoltaics and solar water heating. (My first two real jobs--in New Mexico and then Vermont back in the late '70s and early '80s--were for organizations advancing solar energy, and solar is still dear to my heart.)

But I strenuously resist the temptation of builders, remodelers, homeowners, and commercial building owners to green their buildings simply by slapping solar panels on the roof. Solar should be the icing on the cake--added after doing all the really important work of improving the energy performance of the building envelope and upgrading heating and cooling systems, appliances, and lighting with top-efficiency products. These measures aren't as visible, but they usually yield far greater energy savings, financial return, and environmental benefit than a comparable investment in solar. Homeowners wanting to green their existing homes should start by getting a comprehensive energy audit to identify--and prioritize--energy saving measures. Likely measures will include adding insulation, upgrading windows (perhaps with new, low-e storms), air-tightening, replacing incandescent light bulbs with compact-fluorescent lamps (CFLs), replacing older heating or cooling systems, and switching to more efficient appliances. To reduce water heating costs, start by reducing your use of hot water by installing water-conserving showerheads, clothes washers, and dishwashers. After these investments, if your budget permits, by all means add a solar water heating or solar-electric system.

Anyone thinking of building a new home should hire an architect or designer familiar with ultra-low-energy building practices, including passive solar design (a less noticeable but usually more cost-effective application of solar energy). If you do a really good job with all this and get your heating, cooling, and electrical loads low enough, you then might be able to satisfy all of those needs with solar--creating a "net-zero-energy" house.

The temptation to start with solar is strong, especially with the very attractive 30% federal tax credits that exist for solar systems (see "Tax Credits for Solar Energy Systems"). Such generous solar tax credits, I fear, will result in a whole lot of money going into solar systems that yield considerably less energy savings than would have been realized by putting that money into energy conservation. When solar systems--especially PV systems--are installed on inefficient houses, the percent savings and return on investment can be very low; if you're spending that much money (and the rest of us tax payers are helping out by subsidizing the tax credit) you might as well get some boasting rights!

Yes, you should install solar water heating and solar-electric systems, but before you do that you should invest in the low-hanging fruit of energy conservation.

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Published March 30, 2010

(2010, March 30). Green Building Myth #5: Adding Solar is the Best Way to Green a Home. Retrieved from https://www.buildinggreen.com/blog/green-building-myth-5-adding-solar-best-way-green-home

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Comments

April 1, 2010 - 6:23 pm

Besides the other variables, so much depends on where you are. In Colorado, PV almost always makes sense, while solar HW almost never does. Very insulated, passive solar, all-electric is the ticket.

April 2, 2010 - 2:33 pm

The normal approach to energy conservation is always to make a converstion to compact fluorescents light bulbs. I am becoming a non-believer. While compact fluorescents require less energy than do the "same old/same old" incandescent bulbs, I am beginning to believe that savings only benefits the power company and never the user. I have been running tests for some time now to quantify the life expectancy of compact fluorescents, and it is beginning to seem as those their life expectancy is considerably shorter than fluorescent bulbs that use a 130V filament. MUCH shorter.

Considering the much higher dollar cost of compact fluorescent bulbs versus incandescents, I am beginning to question whether or not these bulbs are more than hype. Now, it is true that normal incandescents purchased in the grocery store have 115 volt rated filaments, 130V filaments are not uncommon and are not more expensive than the weaker bulbs.

It appears to me that the only real savings of energy to be had with light bulbs is to turn off the builbs EVERYtime they are not going to be used, and whenever possible, change lighting systems to LED lights, which are vastly more expensive AND efficient.

April 3, 2010 - 1:59 am

Great points. It's most important to start with an efficient building & then over lay renewable technologies. The same thinking should apply to commercial construction.

April 6, 2010 - 8:15 am

Typical 130v A19 90w bulbs will produce roughly comparable color temperature and lumen output as its direct compact fluorescent replacement. My practical experience is that these lamps will deliver in excess of 2000 hours of use at a cost of around nineteen cents each.

The compact fluorescents that I have been useing as a comparison are failing at a rate that is not remarkably longer than the typical incandesents in use in the same building, and certainly are not delivering sufficient life to warrant the additional initial cost.

April 6, 2010 - 8:58 am

There are a lot of cheap CFL's on the market and many are junk. If you're interested if expanding your comparison try one from a name brand company like GE, Phillips, or Sylvania.

There could also be other things affecting lamp life like frequent switching, power quality, and high temperature in an enclosed fixture. Lamp life is based on lab tests in a controlled environment. It's also the time that 50% of them fail. So half last less than the rated lamp life and half last longer then the rated lamp life.

April 6, 2010 - 6:36 am

All lamps are a ballance of qualities. Improving one trait comes at the expense of other traits.
A typical A-lamp life expectancy is 750-1,000 hours. The 130V lamps can improve this up to 2600 hours. Seems impressive right. The cost of this is reduced light and reduced efficency.
A typical 100W lamp is 1,710 initial lumens per GE online product catalog. 17 lum/W
A 90W, 130V lamp operating at 120V is 80W and 1,095 initial lumens. 13 lum/W

A self-ballested screw base CFL is 23W and 1,600 initial lumens. 69 lum/W.
And it has a 12,000 hour lamp life. And the CRI is 82, which is good color rendering. You just need to allow it to warm up.

April 6, 2010 - 10:52 am

Roger, to respond to your example: Let's say both a 90W incandescent and 23W CFL deliver the same amount of light and last the same 2,000 hours (arguably a worst-case scenario for the CFL).

If you are paying the U.S.-average for electricity (about 12ยข/kWh), then during that 2,000-hour life, the incandescent light bulb will use $21.60 in electricity, vs. $5.52 for the CFL. So the CFL uses $16 less than the Incandescent bulb over that 2,000 hours.

If one were making a purchasing decision based on life-cycle costs, the CFL would be the better deal as long as the difference in price between the incandescent and CFL was less than $16. Except perhaps for some reflector-style CFLs, the cost differential is usually a lot less than $16. Plus, unless your electrical system has problems that are causing the CFLs to fail prematurely (such a voltage surges), the CFLs should, on average, last a lot longer than 2,000 hours, so the economics should be more attractive.