| The table immediately below compares 22 households living in single family homes around Greater Cincinnati in 2004 who volunteered to participate in my survey. Besides noting the widely different rates and volumes of energy use, another important initial observations is that it's apparently not just access to cheaper energy which results in lower energy costs. Very low energy costs are also being achieved by households with more efficient lifestyles and more thermally efficient houses. |
| Annual energy cost per person in this 2004 sample varied from $201 to $862, with the two homes achieving these cost ratios each using the same energy supplies, natural gas and electricity. Using the energy efficiency (EE) and alternate energy (AE) measures column (below) and the "EE/AE Energy Efficiency & Alternate Energy Features" table (below), note that the $201 per person household didn't report having a thermally efficient house, but it did report having a more efficient furnace, mostly compact fluorescent light bulbs, no clothes dryer or dishwasher. The $862 per person household reported no energy efficiency features. The average energy cost per person in this 2004 sample was $540.64. |
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| Annual energy cost measured per the home's square footage varied from 30 cents to $3.69, a ratio of over 12! The 30 cents/sf household is known by Robbins to be an older house retrofitted with passive solar, insulation, efficient windows, an efficient furnace and a small freestanding woodstove, but no air conditioning. It used a half cord of free firewood. The high cost/sf household lived in a thermally unimproved older home. Otherwise they both used natural gas and electricity purchased from the same local utility. The average annual energy cost per sf in this 2004 sample was 79 cents. |
| The consumer value of the energy in this sample is how much energy content was purchased for each dollar spent. This varied from 40 to 102 kBTUs, or thousands of BTUs per each dollar spent. However, the two homes with these varying value ratios used the same kinds of energy, electricity and firewood. The household which got more BTUs per dollar got its firewood for free, while the other household paid for its firewood. The household that paid the most per unit of energy got its electricity from a rural utility with mostly flat billing rates, while the household that paid the least per unit got its electricity from an urban utility with declining marginal electricity rates during the heating season for monthly purchases over 1000 kWh per month. The average BTUs per dollar in this 2004 sample was 66. |
| BTU/sf-dd is a measure of how much total annual energy was purchased divided by the size of the conditioned floor area and the local degree-days. Degree-days (in this survey, both heating and cooling seasonal totals summed) and floor areas are referenced to allow easier analysis and comparison of home and personal energy performance even when structures are different sizes or located in somewhat different climates or climate years. (Read in my 2001 and 2002 survey reports for more detailed discussion about this rating category.) In this category, the best performer achieved 2.57 BTU/sf-dd, while the worst achieved 41.38, a performance ratio of over 16 ! That household was so high probably because it had 7 occupants living in less than 1000 sf, a very high occupant density of 137 sf/person. The 2.57 BTU/sf-dd performance was for 2 persons in 4000 sf, a very low occupant density of 2000 sf per person. This best performer is also known to live in a superinsulated newer home, while the worst performer reported no energy efficiency improvements and probably lived in an older home. The average BTU/sf-dd in this 2004 sample was 8.86. |
| KBTU/p-dd is a measure of total energy purchased divided by the number of occupants served by that energy and the local degree-days (heating and cooling summed). This measurement allows climate-corrected comparisons of per-person energy use year to year or climate to climate, but does not consider how much living space is used per person. This measurement is useful to offset the bias which appears to favor lower occupant density in the above BTU/sf-dd measurement. In this category, the best performance was 2.24 BTU/p-dd, with a family of 4 living in a 1200 sf older home and reporting modest energy efficiency improvements. The worst performance was 12.46, another family of 4 but in a much larger 4556 sf older home and reporting fewer energy efficiency improvements. The average BTU/p-dd in this 2004 sample was 6.11. |
| Ideally, the best performing household would score well in both categories, demonstrating superior per-person as well as per-home-size performance. Line #9 shows such a household, the only home which received my "SUPER" rating in both categories. This family of 4 lives in a newer 2400 sf superinsulated well-daylit passive solar home with efficient appliances, HVAC equipment and lighting. Occupant density is 1 person per 600 sf, while average density for this survey's sample was 1 person per 946 sf, slightly more than 50% more floor per person. |
| Ratings of super, efficient, average and inefficient were assigned to each of these last two measurements based on the following scales: |
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| Read in my 2001 and 2002 survey reports for more detailed discussion of how this ratings scale developed. |
| The heating (htg) and cooling (clg) degree-days (DD) for the Greater Cincinnati International Airport for 2004, as reported by NOAA: |
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| The ratings in this 2004 sample appear biased on the side of more efficiency, at least based on the above ratings scale. If there is a bias toward more efficiency in this survey, it could be because there is more-than-average interest in energy efficiency among persons who typically contact Robbins or which Robbins contacts to participate in this survey. |
| E-mail: johnfrobbins@insightbb.com |
