Energy efficiency - Trends, determinants, trade-offs and rebound effects with examples from Swedish housing

Doktorsavhandling, 2007

This thesis is based on five separate papers. The first paper analyses the development of the Swedish building sector over time by decomposing CO2 emissions in underlying trends, and studying separate energy use trends for existing buildings, new buildings and best available technology. The results show rapid improvements in energy efficiency during the seventies, but that this development stagnated in both existing and new buildings in the late eighties and nineties, and that the diffusion of energy efficient technologies appears to be slow. The specific energy use for heating in average new buildings is twice as high as in the best performing buildings 20 years ago. The second paper deals with the causes of these trends, including an econometric part and a qualitative part. The third paper handles indirect energy use and CO2 emissions coupled to the production phase of buildings. Results from an input-output analysis are disaggregated into activities and materials which can be compared to results from bottom-up studies. The results show only minor differences for production and processing of building materials, but for other upstream sectors such as transport, services and production of machines, the input-output analysis gives much higher values. This implies that bottom-up studies may underestimate the relative importance of energy use in the production phase in relation to the use phase. The forth paper handles rebound effects of energy efficiency improvements caused by decreasing prices of energy services as well as by reduced direct energy expenditures which can be redirected to other goods and services. Different parameter assumptions are tested. The total rebound effects of energy efficiency appear to be in the range of 5 to 15 percent in most cases, but cases with low or negative investment costs for energy efficiency may result in higher values. The fifth paper is an optimization study on the potential trade-offs between energy efficient supply systems (combined heat and power/district heating) and energy efficient end-use of heat. The cost effective solution depends to a large extent on the relation between the electricity price and the CO2 price. This in turn depends on what technologies that are available for electricity production. Without alternatives to basic condensing electricity production, high CO2 prices result in high electricity prices, high profitability of combined heat and power and thus little incentive to reduce heat demand. In contrast, if low CO2 alternatives are available, the electricity price levels out at high CO2 prices. In this case, end-use efficiency measures may be cost effective also in buildings with district heating.