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Home Energy Magazine Online May/June 1998


TRENDS

Florida Home Gets Energy Makeover

An installer from the Florida Solar Energy Center checks the wiring on the new 15-SEER air conditioner installed in a Florida home. In a surprise to the researchers, the air conditioner was less cost-effective to retrofit than some usually appliances that are usually ignored.
Table 1: Savings by Measure
Retrofit Installed Cost Estimated Annual Savings Simple Payback (years) Simple Return on Investment
Radiant barrier system $1,100 400 kWh $40 30 3%
High efficiency air conditioner $3,600 3,300 $280 13 8%
Solar water heater $1,600 1,000 $80 20 5%
Efficient pool pump $300 1,200 $100 3 33%
High efficiency refrigerator $1,000 2,200 $190 5 20%
Attic ventilation $400 50 $5 110 1%
Lighting  $400 1,300 $120 4 25%
TOTAL $8,500* 9,500* $800*    
*Numbers do not add up due to rounding
Pop Quiz! An energy efficiency contractor with an all but unlimited budget has retrofitted a house in Florida. It's all-electric, with a pool, and before the retrofit, it consumed 21,000 kWh annually. The retrofitter armed the home with a virtual arsenal of energy efficiency measures: SEER-15 air conditioner, solar water heater, super-efficient refrigerator, more efficient pool pump, radiant barrier, attic ventilation, and compact fluorescent lights. What were the most cost-effective retrofit measures?

According to the Florida Solar Energy Center (FSEC), the answer is pool pump, lighting, and refrigeration. FSEC conducted a two-year study of such a house to learn how far energy use could be reduced in existing Florida houses. The answer--a 45% reduction in electricity use (about 9,000 kWh)--demonstrated that such cuts are feasible with today's technology. While these results are pretty impressive, it was the cost-effectiveness of the lower-price measures that the researchers deemed to be one of the study's most important conclusions.

Replacing the SEER-9 air conditioner system with a SEER-15 system saved the greatest amount of money and energy per year, reducing space cooling consumption by 50% (3,300 kWh) (the duct system was relatively tight, as was the building envelope). However, because of its high purchase cost--despite a utility rebate--it will take 13 years for the homeowners to recoup their investment. According to Danny Parker, one of the authors of the study, this measure would have been far more cost-effective at the time the existing air conditioner expired and the choice was between a high efficiency unit and a standard SEER-10 model.

The radiant barrier system, solar water heater, and attic ventilation all had similar results. Although air conditioning use was reduced by about 5% after installing a radiant barrier, the $1,100 barrier saved only $30 per year. The solar water heater--an add-on system--with an installed cost of $1,650, had a simple payback of 20 years. And although the attic reached 135°F on peak summer days, ventilating with ridge vents would take 110 years to pay back.

On the other hand, installing a more efficient pool pump, switching to compact fluorescents, and replacing the refrigerator with a high efficiency unit drastically lowered the payback period to between 3 and 5 years.

Replacing the pool pump was the most cost-effective measure, with a simple payback of 3 years. The original 1-horsepower pump for the 15,000-gallon pool was oversized. This is standard industry practice, according to Parker. Replacing the pump with a 3/4-horsepower unit saved approximately 1,200 kWh per year and offered a appealing return on investment of approximately 30%. After the third year that translates into $100 per year of untaxed profit. The homeowner noticed no difference in the performance of the pool cleaning system after the installation.

Lighting savings were second on the cost-effectiveness list, but the deck was stacked a bit. Because of the extensive use of halogen lamps, including torchieres, (see Changing Attitudes on Changing Lamps, p. 31), there was a total possible load in the house of almost 4,000 watts. Two torchieres alone were using over 900 watts, while also adding a sensible load of 3,000 Btu per hour on the air conditioner. Compact fluorescent lamps (CFLs) brought the lamps' electrical demand down to only 39 watts each. At 25% of the house's annual electricity use, lighting was the second largest end use after air conditioning (40%). After the retrofit with CFLs and other lights, the return on the $400 investment was 29% per year, with additional savings from lowering the load on the air conditioner.

Finally, replacing the existing refrigerator in the Florida home with a super-efficient model reduced refrigerator energy use by 70%. When the installation cost and annual monetary savings are taken into account, this meant a 20% return on the money. And like the efficient lights, the more efficient refrigerator contribute less to the internal heat gain of the house, saving even more money.

FSEC did not design this retrofit project as an economic demonstration. They wanted to push savings as far as they could while using off-the-shelf technologies. A prior experiment by FSEC on lighting alone found that replacing all the lighting in a home with efficient lamps was economical, but that a few lamps accounted for most of the profit (see Florida House Aglow with Lighting Retrofit, HE Jan/Feb '97, p. 21). Similarly, this entire retrofit was profitable, with a simple return on investment of 14%, but some measures turned out to be much more profitable than others. The full report describing the project (Measured Energy Savings of a Comprehensive Retrofit in an Existing Florida Residence) is available from FSEC or online at their Web site: http://fsec.ucf.edu).

--Tom Sluis

 


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