GREEN SYSTEMS | ALTERNATIVE ENERGY | B. SHADY CONTINUED FROM PAGE 72
taxes to determine the after tax equivalent rate of $0.16/kwh BS:What overall conclusions can be
made from the SPER chart? DK: In the last year, solar has become
cost effective in almost every major city in the U.S. The simple way to use this chart is to compare column 9, the SPER, to column 11, which is the after tax equivalent rate of your electricity. In 31 of the 40 cities shown, the SPER is lower than the after tax grid electric rate. Homeowners understand that their mortgage is tax deductible but that their utility bill is not. That is why we compare the SPER to the after tax equivalent electric rate. If you believe that grid prices will
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increase, another thing to note on this chart is column 9, the SPER rate, compared to column 12, which calculates the average price per kwh if the grid rate increases 5% a year. As you can see, in all 40 cities surveyed, the solar electric rate is significantly less than the grid rate over the 30-year period. So, even in cities with harsh climates, no solar incentives and low electric rates, you can make the case for producing your own electricity and building a net zero energy house. BS: You have made a good case for the
homebuilder to use solar power for lighting, air conditioning and appliances. You obviously need electricity for those uses. For space heating and domestic hot water, isn’t it more cost effective to use fossil fuels such as natural gas, propane and fuel oil? DK: The introduction of the air-to-
water heat pump, which I mentioned earlier, can make use of solar electric for space heating and domestic hot water cost efficient and practical. To demonstrate my point, I developed Table 2, which compares the use of an air-to- water heat pump with natural gas, fuel oil and propane. For simplicity, all units have been converted to kwh/year. (See Table 2.) As you can see, in the 40 cities
surveyed, using solar in conjunction with an air-to-water heat pump is significantly more cost effective than using either fuel oil or propane. This can be seen by comparing column 4 with columns 7 through 10. In 31 of the 40 cities surveyed, the cost of using solar with an air-to-water heat pump is the same or less than the after tax rate of using natural gas, shown in column 6. In colder climates, however, a geo exchange heat pump may be a better choice than an air source heat pump. I think that hydronic contractors can now offer their customers an alternative to fossil fuels.
e Turn to B. SHADY on p 76
phc january 2011
www.phcnews.com
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