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This report presents the results of an impact evaluation of the Manufactured Housing Acquisition Program. This evaluation was conducted for Bonneville by Pacific Northwest Laboratory to determine MAP's energy impacts and cost-effectiveness. Two other reports supplement this overall report on the evaluation. Lee et al. (1995) provides technical details of the study. Sandahl, Lee, and Chin (1995) presents detailed information about the homeowner survey conducted for this evaluation.

To estimate MAP savings, we developed MAP and baseline home samples. We conducted telephone interviews to collect home and owner information for both homes. We completed 167 MAP occupant interviews and collected 134 utility billing release forms. For the baseline homes, we completed 183 interviews and obtained signed utility billing release forms from 123 respondents.

We conducted a three-tiered analysis of the utility billing data to estimate program electricity savings. The first (a raw billing data comparison and simple regression analysis) and second-tier (PRISM) analysis provided useful findings for the third-tier analysis by which program savings were estimated.

The third-tier approach used a conditional demand-type regression analysis to analyze monthly energy consumption, taking into account significant factors likely to influence electricity usage. We used the regression results to estimate energy savings under "normal" weather conditions for each climate zone.

For purposes of estimating savings, we had to define a comparison home based on typical characteristics. The "pre-MAP baseline" home represents a home with dimensions typical of current homes, but with an efficiency level typical of homes built prior to MAP. The electricity savings estimates were very sensitive to assumptions made about the use of non-electric (primarily wood) space heat; about 20% of our combined sample of homes used some non-electric heat. We found no consistent evidence that MAP homes used non-electric heat more often.

We used two approaches to estimate energy savings impacts of MAP. In the first, we calculated electricity savings based on the overall observed mix of heating types. In the second case, we calculated energy savings based on the assumption that all heating was supplied by an electric resistance furnace.

The savings estimates were based on the third-tier, regression results. Acquisition [acquired] energy savings were calculated as the energy consumption difference between pre-program baseline and MAP homes. These were the direct energy savings associated with homes built under MAP. MAP, however, had significant market transformation effects not accounted for by the acquisition [acquired] savings.

MAP occurred in two phases. During Phase 1, April 1992 through October 1994, the original national HUD code was in effect and utilities paid manufacturers $2,500 for each MAP home. Phase 2 started after October 1994, when a new, more efficient HUD code went into effect and the payment declined to $1,500. We estimated energy savings for homes built during each phase. Our estimates of regional average energy savings for homes built during Phase 1 varied from about 3,800 to 4,700 kWh/year and for homes built during Phase 2 varied from about 2,500 to 3,000 kWh/year.

We determined cost-effectiveness by calculating levelized costs using a methodology published by Bonneville. Under one perspective, levelized costs were based on regional system costs. From this perspective, electricity savings were acquired for MAP homes at a regional average cost of about 1.7 cents/kWh (17 mills/kWh). From the second perspective, the program costs borne by Bonneville for MAP were about 2.0 cents/kWh (20 mills/kWh). Overall, these costs were low enough that the program, based on acquisition [acquired] energy savings alone, was cost effective.

Although too early to tell definitively, MAP appeared to have made fundamental changes in the market for energy efficient manufactured homes in the Pacific Northwest. More than 50,000 electrically heated manufactured homes sited in the region since April 1992 have been built to MAP specifications. Consumers have come to expect the MAP features and dealers have become used to selling them. Although it was exactly what the market would look like with the end of MAP, the program appeared to have caused a significant, lasting transformation.

We analyzed potential market transformation effects from a conceptual viewpoint. Our results suggested that MAP's market transformation benefits probably reduced the levelized cost to utilities by 40% or more.

Our results indicated that MAP was cost effective overall, even when viewed as just an electricity savings acquisition program. Cost-effectiveness did vary by climate zone, but the program was cost-effective in all cases from the regional system perspective. From the Bonneville system perspective, the cost-effectiveness in the mildest climate zone (climate zone 1) was questionable. Accounting for the likely large market transformation impacts, the program was unquestionably cost-effective in all zones.

This study raised the following analytic issues:
  • Cost-effectiveness depends significantly on the energy efficiency assumed for pre-program baseline manufactured homes.
  • Pre-program savings estimates were considerably larger than our estimates based on billing data from MAP and non-MAP homes.
  • The relationship between temperature and energy consumption in regression analysis models needs further investigation.
  • Zoning may diminish the effect of building envelope efficiency improvements.
  • Mechanical ventilation may have affected energy savings of MAP homes

In addition to analytic findings, this study produced the following program design and policy findings and observations:
  • On the average, the utility payments to manufacturers appeared to have exceeded the manufacturers' (and even the wholesale) incremental wholesale costs associated with MAP homes: it is likely that smaller utility payments could have accomplished the program purposes while reducing program costs.
  • MAP appears to have caused a significant transformation in the manufactured housing market in the Pacific Northwest: further studies should be conducted to document and verify the market transformation effects caused by MAP.
  • MAP ended sooner than anticipated and with less preparation than desired: an off-the-shelf strategy to transition out of the program would have helped maintain the good relationships and positive expectations established by the program and future programs, especially market transformation programs, should incorporate a transition strategy in the initial program plan

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