Evaluation of utility residential energy conservation programs: A Pacific Northwest example

This paper describes a detailed quantitative evaluation of the Residential Weatherization Pilot Program, operated by the Bonneville Power Administration from 1980 through 1982. The program provided free energy audits to more than 6000 electrically-heated homes and gave zero-interest loans to weatherize almost 4000 of these audited homes. The total cost of the program was almost $8 million.Using actual electricity consumption records for program participants and nonparticipants, we calculated the energy-saving effect of the pilot program in several ways and always reached the same conclusion. Households that received an audit and weatherization loan reduced their annual electricity consumption by about 3500 kWh relative to what they would have done without the program: this 3500 kWh is the saving that can be directly attributed to the program.Using a simple net present worth approach, we computed program benefits and costs for participating households, the BPA power system, and the Pacific Northwest region as a whole. Under a wide range of assumptions concerning discount rate, years until the weatherization loan is repaid, program energy saving, and BPA's marginal cost of power, the program is economically attractive from all three perspectives.     

Statistical analysis of residential building energy consumption in Tianjin

To analyze the effect of energy conservation policies on energy consumption of residential buildings, the characteristics of energy consumption and indoor thermal comfort were investigated in detail in Tianjin, China, based on official statistical yearbook and field survey data. A comprehensive survey of 305 households indicates that the mean electricity consumption per household is 3215 kWh/a, in which annual cooling electricity consumption is 344 kWh/a, and the mean natural gas consumption for cooking is 103.2 m³/a. Analysis of 3966 households data shows that space heating average intensity of residential buildings designed before 1996 is 133.7 kWh/(m²·a), that of buildings designed between 1996 and 2004 is 117.2 kWh/(m²·a), and that of buildings designed after 2004 is 105.0 kWh/(m²·a). Apparently, enhancing the performance of envelops is effective in reducing space heating intensity. Furthermore, the results of questionnaires show that 18% of the residents feel slightly warm and hot respectively, while 3% feel slightly cold in winter. Therefore, the electricity consumption in summer will rise for meeting indoor thermal comfort.     

Determinants of electricity use for residential water heating: The hood river conservation project

Because 85% of the homes in the Pacific Northwest have electric water heaters, water heating is the second most important residential electricity end-use in the region (second to space heating). This paper analyses the determinants of water-heating electricity use, using end-use load data and responses to a detailed home interview. These data are available for 142 homes in Hood River, Oregon.On average, these homes used 5000 kWh/yr for water heating. Almost 60% of the household-to-household variation in electricity use was explained with eight variables in a simple regression model. The number and ages of household members are the strongest determinants of electricity use: use increases by roughly 1000 kWh/yr with each additional household member. Other statistically significant determinants of water-heating electricity use are hot-water temperature, water-heater location, number of showers in the home and house type.Electricity use varies considerably throughout the year (as well as across households). Weekly usage was 50% higher in mid-winter than in summer. About half of this temporal variation is due to changes in outdoor temperatures and half is due to seasonal changes in behavior (i.e. increased use of hot water in winter).     

Actual energy savings after retrofit: Electrically heated homes in the Pacific Northwest

The Bonneville Power Administration operated an interim Residential Weatherization Program during 1982 and 1983 throughout the Pacific Northwest. The program offered free home energy audits and financial incentives to help pay for installation of recommended retrofit measures in electrically heated homes. Almost 104,000 homes were retrofit during the two years the program operated at a cost to BPA of almost $160 million.This study analyzes actual electricity savings for about 1000 homes that participated in the BPA program in 1982 or 1983. The data for each household include electric utility bills for one year before and one year after retrofit; daily temperature data for weather stations near these households; energy audit reports and postinstallation inspection forms; and information on household demographics, structure characteristics, and heating fuels from surveys conducted in Fall 1983 and June 1984.The major factors related to actual household electricity savings after retrofit are: preretrofit electricity use, audit estimate of electricity saving for measures installed, changes in electricity prices, and changes in primary or supplemental heating fuels (especially shifts to and from wood). Together, these factors explain no more than half the variation across households in actual savings.     

Estimating energy savings due to conservation programmes: The BPA residential weatherization pilot programme

The Bonneville Power Administration operated a residential weatherization pilot programme from 1980 to 1982. The programme provided free home energy audits to more than 7000 electrically heated homes in the Pacific Northwest and gave zero-interest loans to weatherize over 4000 of these homes. The total cost of the programme was $11 million. This paper describes several mehtods used to estimate the net energy-saving effect of the BPA programme (ie the electricity saving that could be directly attributed to the programme). The simplest method ivolves estimation of weather adjusted annual electricity consumption for each household. The second approach uses this weather adjusted consumption as the dependent variable in a pooled time-series cross-section regression model of electricity use. The third approach involves estimation of qualitative choice models of the decisions to retrofit and to participate in the BPA programme. Results from these models are used to define Mills ratio terms that are then used as explanatory variables in the regression model of the second approach. The range in estimated programme saving, given the diversity of analytical methods used, is surprisingly small — 3100–3300 kWh/year per average programme participant.     

Connecticut's residential conservation service: An evaluation

CONN SAVE is a non-profit consortium of electric and gas utilities in Connecticut, established to deliver services mandated by the federal Residential Conservation Service. This article describes a quantitative evaluation of the programme which involved collection of several types of data from CONN SAVE, fuel suppliers and households.Data from home energy audits and on-site home interviews were analysed in terms of conservation potentials as of Spring 1981. Potential for space-heating energy saving was roughly 15% greater in participant homes than in control homes and for water heating energy saving was slightly larger for control homes. Participant homes installed many more retrofit measures than control households and, as a consequence, were expected to cut their annual energy costs by 2–3 times as much as the control households - 18 MBtu vs 7 MBtu ($160 vs $60). Hence, the CONN SAVE audit was effective in stimulating additional retrofit action on the part of participants.     

Annual variations of temperature in a sample of UK dwellings

The internal temperatures of 25 households in Northern Ireland were measured in each house at four locations: the bedrooms, living rooms, halls and kitchens, and analysed on seasonal, monthly and daily bases. In 80% of the homes the winter average daily temperature was between 15 °C and 20 °C and in summer between 20 °C and 23 °C, therefore maintaining a reasonably comfortable temperature throughout the year. In 14% of the homes, the daily average temperature was above 21 °C throughout the year, suggesting a higher household temperature than required for comfort, thus exhibiting wasteful energy behaviour. Three percent of the homes did not use their heating adequately and the winter average temperature was below 15 °C. For the majority of households, the highest indoor temperature was in August and the lowest in February. In general the peak temperatures of households occur in the evening after 8:00 pm. The peak bedroom temperatures occur between 10:00 pm and midnight and in the morning after 8:00 am. The peak living room temperature is generally in the evening while it is occupied. Correlations between the temperature difference between indoor and outdoor temperatures with outdoor temperature have been developed for each house and the four locations. The relationship between the fluctuations of average daily temperature with annual average temperature has been established.     

Quantification of energy savings from Ireland’s Home Energy Saving scheme: an ex post billing analysis

This paper quantifies the energy savings realised by a sample of participants in the Sustainable Energy Authority of Ireland’s Home Energy Saving (HES) residential retrofit scheme (currently branded as the Better Energy Homes scheme), through an ex post billing analysis. The billing data are used to evaluate: (1) the reduction in gas consumption of the sample between pre- (2008) and post- (2010) scheme participation when compared to the gas consumption of a control group, (2) an estimate of the shortfall when this result is compared to engineering-type ex ante savings estimates and (3) the degree to which these results may apply to the wider population. All dwellings in the study underwent energy efficiency improvements, including insulation upgrades (wall and/or roof), installation of high-efficiency boilers and/or improved heating controls, as part of the HES scheme. Metered gas use data for the 210 households were obtained from meter operators for a number of years preceding dwelling upgrades and for a post-intervention period of 1 year. Dwelling characteristics and some household behavioural data were obtained through a survey of the sample. The gas network operator provided anonymised data on gas usage for 640,000 customers collected over the same period as the HES sample. Dwelling type data provided with the population dataset enabled matching with the HES sample to increase the internal validity of the comparison between the control (matched population data) and the treatment (HES sample). Using a difference-in-difference methodology, the change in demand of the sample was compared with that of the matched population subset of gas-using customers in Ireland over the same time period. The mean reduction in gas demand as a result of energy efficiency upgrades for the HES sample is estimated as 21 % or 3,664?±?603 kWh between 2008 and 2010. An ex ante estimate of average energy savings, based on engineering calculations (u value reductions and improved boiler efficiency and use through heating controls), suggests a technical reduction potential of 5,676 kWh per dwelling. Equating this with the gas reduction in the sample suggests a shortfall of approximately 36?±?8 % between technical potential and measured savings. This shortfall includes the effects of direct and indirect rebound effects, variations in ex ante assumptions and achieved u values and efficiencies for upgraded dwellings. The profile of household characteristics in the HES sample is influenced by the self-selected nature of scheme participants. Self-selection bias and other possible biases in the sample data impact on the validity of the comparison. Data limitations for individual households across explanatory variables in the control and treatment groups precluded corrections for these biases in the sample; however, the profiles of separate comparable data sets were used where possible to quantify the differences in the explanatory variables and how these might impact on the measured energy saving with reference to the relevant effects identified in the literature.     

Energy in american homes: Changes and prospects

Average energy consumption per U.S. household has fallen by just under 20% in the last ten years. Much of this drop occurred after 1979, when gas and electricity prices as well as oil prices rose in real terms. The response of households to higher prices has involved physical modifications on and in the home and changes in behavior. Many actions have been taken by households, but the most important single factor has been a significant reduction in indoor temperatures. The greater energy efficiency of new homes and appliances has also helped to depress residential energy demand, although improvements have levelled off in the last few years. There are signs that the momentum of energy conservation is less now than it was 2 years ago, but it appears that energy prices will be high enough to discourage households from returning to former energy-using practices. Along with the continued replacement of homes and appliances with more efficient models, and other factors such as the migration to wanner regions and the movement to more apartments and smaller homes, this will probably keep U.S. residential energy consumption at about its present level through the 1980s.     

Energy savings from the Minnesota low-income weatherization programme

The 26 local Community Action Agencies in Minnesota administer a federal programme to audit and retrofit homes occupied by low-income households. This programme aims to improve the thermal performance of these homes and so reduce the economic hardship faced by these households because of high and rising fuel prices. A key question concerns the actual energy savings that can be attributed to the programme. The work reported here involved collection and analysis of fuel consumption records from low-income households throughout Minnesota. Data were obtained from 59 households that had received weatherization services and from 37 households that were eligible for assistance but had not yet been weatherized. Comparisons of fuel consumption across the two groups for the 1976–1977 and 1977–1978 winters showed that the average saving due to weatherization was 13% of total household energy use. Based on fuel prices that prevailed in 1979, the cost of weatherization is likely to be repaid with lower fuel bills in 3–4 years.     

Assessing the consumers’ willingness to adopt a prepayment metering system in Nigeria

Despite the rising popularity in the adoption and usage of prepayment meters, little is still known about the drivers of its adoption. We examine the willingness to adopt prepayment metering (PPM) for a sample of Nigerian households that were not prepayment users. Double-hurdle models were estimated to account for households’ decisions concerning billing system switching behaviour and households’ willingness to pay (WTP). The estimated results revealed that decisions to adopt a prepayment meter are significantly affected by current electricity spending, current billing method and the split incentive problem. Whereas current electricity spending significantly increased the tendency to adopt PPM, the split incentive problem reduced the probability of adoption. Although unmetered consumers were more likely to express a willingness to adopt a PPM system than post-paid customers, they did not intend to pay a significantly higher amount to obtain the prepayment service. Income did not play a significant role in decision-making concerning PPM adoption and the corresponding WTP amount. These results cast doubt on the validity of the widely held belief that low income may be responsible for PPM adoption, reflecting the widespread usage of PPM by low-income households.     

Estimating the potential for electricity savings in households

Improving efficiency in the use of energy is an important goal for many nations since end-use energy efficiency can help to reduce CO₂ emissions. Furthermore, since the residential sector in industrialised countries requires around one third of the end-use electricity, it is important for policy makers to estimate the scope for electricity saving in households to reduce electricity consumption by using appropriate steering mechanisms. We estimate the level of technical efficiency in the use of electricity using data from a Swiss household survey. We find an average inefficiency in electricity use by Swiss households of around 20 to 25%. Bottom-up economic-engineering models estimate the potential in Switzerland to be around 15%. In this paper we use a sub-vector input distance frontier function based on economic foundations. Our estimates lie at the upper end of the electricity saving potential estimated by the afore-mentioned economic-engineering approach.     

Living in cold homes after heating improvements: Evidence from Warm-Front,England’s Home Energy Efficiency Scheme

ObjectiveTo investigate explanatory factors for persistent cold temperatures in homes which have received heating improvements.DesignAnalysis of data from a national survey of dwellings and households (in England occupied by low-income residents) that had received heating improvements or repairs under the Warm Front Scheme.MethodsOver the winters of 2001–02 and 2002–03, householders recorded living room and main bedroom temperatures in a diary. Entries were examined for 888 households, which had received high level heating interventions. Two hundred and twenty-two households were identified as occupying cold homes, with mean bedroom temperature below 16 °C or mean living room temperatures below 18 °C. Binary logistic regression was used to model dwelling and household features and then occupants’ behaviour and attitudes in the ‘cold homes’ sub-set compared with the remainder of the high intervention group. Seventy-nine supplementary, structured telephone interviews explored reasons given for lower temperatures. Using graphical and tabular methods, householders preferring cooler homes were distinguished from those who felt constrained in some way.ResultsCold homes predominate in pre-1930 properties where the householder remains dissatisfied with the heating system despite major improvements funded by Warm Front. Residents of cold homes are less likely to have long-standing illness or disability, but more likely to experience anxiety or depression. A small sample of telephone interviews reveals those preferring lower temperatures for health or other reasons, report less anxiety and depression than those with limited control over their home environment. Their ‘thermal resistance’ to higher temperatures challenges orthodox definitions of comfort and fuel poverty.     

Measured winter and spring-time indoor temperatures in UK homes over the period 1969–2010: A review and synthesis

This paper presents a review and synthesis of average winter and spring-time indoor temperatures in UK homes measured over the period 1969–2010. Analysis of measured temperatures in a sample of solid wall dwellings in the UK, conducted as part of the CALEBRE research project, is included. The review suggests that, for periods when occupation was likely, there has been little or no increase in winter and spring-time average living room temperatures over the last 40 years, with average recorded living room temperatures having been historically lower than the WHO-recommended value of 21 °C. Correspondingly, for periods of likely occupation, average bedroom temperatures appear to have increased. Compared with non-domestic buildings, there have been fewer investigations of domestic thermal comfort, either in the UK or elsewhere, and hence the paper also calls for further detailed investigations of domestic indoor temperatures during occupied hours together with thermal comfort evaluations in order to better understand domestic thermal environments. Based on suggestions from the limited range of studies available to date, living room temperatures may need to be maintained within the range 20–22 °C for thermal satisfaction, though this requires confirmation through further research. The study also emphasises that improving the energy efficiency of homes should be the primary means to effect any increases in indoor temperatures that are deemed essential. Considerations for future policy are discussed.     

What is the relationship between built form and energy use in dwellings?

Energy is used in dwellings to provide four services: space heating, hot water, lighting and to power appliances. This paper describes how the usage of energy in a UK home results from a complex interaction between built form, location, energy-using equipment, occupants and the affordability of fuel. Current models with standard occupancy predict that energy use will be strongly related to size and built form, but surveys of real homes show only weak correlations, across all types of dwelling. Recent research has given us insights into occupancy factors including preferred comfort, ‘take-back’ from thermal efficiency improvements, and patterns of electricity use. Space heating is on a downward trend and is low in new dwellings. Energy use for lights and appliances, which is only weakly related to built form, is increasing. Strong legislation, combined with low-carbon technologies, will be needed to counteract this trend. Future challenges discussed include increases in real energy prices and climate change mitigation efforts, which are likely to improve the existing stock. Challenging targets are now in place for new housing to move towards low or zero energy and carbon standards. In the longer term, dwellings will demand less energy. Alternatives to gas for space heating will be increasingly common, including ground source heat and local combined heat and power (CHP) from biomass, while electricity could come from a more decarbonised electricity system. However, these improvements must be set alongside a demand for many new homes, demographic trends towards smaller households, and a more holistic approach to overall carbon use including personal transport.     

The Kansas City warm room project: Economics,energy savings and health and comfort impacts

The warm room retrofit is a response to a common problem: how to stay warm in a large, poorly insulated house during the coldest parts of winter. The problem is especially acute for low-income and elderly homeowners who may not have sufficient resources to improve the thermal integrity of their entire house. Although still an experimental technique, the warm room retrofit has the potential for achieving significant energy savings in houses at costs similar to those currently allocated by low-income weatherization programs. The retrofit is a combination of zoning, heating systems modification and insulation which allows the occupant to heat selected areas of her home while maintaining the unused areas at a cooler temperature. This study presents the results from a retrofit project in Kansas City, sponsored by the Urban Consortium in 1985–1986. Nine houses were selected for the study, four controls and five houses that received the warm room retrofit. The houses are all single-family detached structures, occupied by low-income owners (with the owners' ages between 60 and 80 yr), and heated with gas-fired forced-air or gravity-fed furnaces. The warm zone was designed to include the kitchen, bathroom, and one to two additional rooms depending on family size. The costs of the retrofit averages $1425 per house. Our analysis included regressions of total gas use vs outdoor temperatures to measure savings, which averaged 26%. Because of potential health and safety problems, we also measured indoor air quality before and after the retrofit, sampling levels of indoor radon, nitrogen dioxide, and formaldehyde. An important part of the study was to determine occupant response and the acceptability of the retrofit. The residents participated in the design of the retrofits, and were interviewed after the retrofits were installed to determine improvements in comfort and their satisfaction with the results.     

Residential energy consumption patterns: the case of Lebanon

In an attempt to fill a significant gap in baseline information, 509 households have been studied to analyse the residential consumption patterns in the urban environment in Lebanon. The average annual household energy consumption has been found to be 6907 kWh, whereas per capita consumption is 1727 kWh. Seasonal and monthly variations are analysed indicating increased energy consumption in the summer months accounting for 28% of total annual consumption. Correlations are indicated for energy consumption with apartment price, area, income and number of residents. Multiple regression analysis indicated statistical significance of income, area and number of residents to the energy consumption. Based on current consumption and electricity generating technologies, 1.6 tons of CO₂, 7.3 kg of SO₂ in addition to other pollutants are generated per resident. Comparative analysis indicates that Lebanon has electricity consumption similar to that of Western Europe, paving the way for significant energy saving potential. Copyright © 2005 John Wiley & Sons, Ltd.     

Multifamily energy-efficiency retrofit programs: a Florida case study

Multifamily buildings are an important target for efficiency improvements because of their energy savings potential and housing market share. Yet few multifamily retrofit projects have been completed in hot-humid regions and even fewer studies have measured and verified savings from such projects. Addressing this gap, the purpose of our research is to assess the impacts of energy-efficiency upgrades to multifamily buildings in Orlando, FL. Specifically, we measure the first-year electricity savings from retrofits to 232 units in four apartment complexes. Annual savings per unit averaged 2094 kWh (22 %) and ranged from 1700 kWh (18 %) to 3811 kWh (29 %) across complexes. Monthly savings ranged from 48 kWh (9.4 %) in December to 340 kWh (31 %) in August. From these core findings, we estimate that tenants in treatment units saved an average of $272 on their electric bills. We also find evidence to support a strategy of targeting upgrades to improve overall savings and program cost-effectiveness. Results are being used to guide development of a utility demand-side management program for multifamily property owners. Progress in this market requires additional pilot projects, access to utility data, reliable measurement and verification of savings, and innovative financing structures.     

Energy efficiency in the British housing stock: Energy demand and the Homes Energy Efficiency Database

The UK Government has unveiled an ambitious retrofit programme that seeks significant improvement to the energy efficiency of the housing stock. High quality data on the energy efficiency of buildings and their related energy demand is critical to supporting and targeting investment in energy efficiency. Using existing home improvement programmes over the past 15 years, the UK Government has brought together data on energy efficiency retrofits in approximately 13 million homes into the Homes Energy Efficiency Database (HEED), along with annual metered gas and electricity use for the period of 2004–2007.This paper describes the HEED sample and assesses its representativeness in terms of dwelling characteristics, the energy demand of different energy performance levels using linked gas and electricity meter data, along with an analysis of the impact retrofit measures has on energy demand. Energy savings are shown to be associated with the installation of loft and cavity insulation, and glazing and boiler replacement. The analysis illustrates this source of ‘in-action’ data can be used to provide empirical estimates of impacts of energy efficiency retrofit on energy demand and provides a source of empirical data from which to support the development of national housing energy efficiency retrofit policies.