Q&A - Result

Methodology

• What is the best indicator to analyse energy efficiency trends of cars?

  For cars three main indicators can be used to characterise their energy efficiency:

  • the specific energy consumption in litres/100 km (l/100 km), also expressed in km/l in America (in miles per gallon or mpg in the US);
  • the specific energy consumption in energy unit in GJ/km (or koe/km);
  • the specific consumption per passenger-km in MJ/pkm (or goe/pkm).

  The first indicator (litre/100 km) shows the effect of technological improvements, driving behaviour and fuel shift.

  The second indicator (MJ or koe/km) takes in addition into account changes in the fuel mix (i.e. in the average calorific value of motor fuels, in Joule or toe/litre). This fuel shift can come from a substitution between gasoline and diesel or from the penetration of biofuels. If the focus is on actual vehicle improvement, this fuel shift effect should be isolated by defining separate indicators for the different fuels, e.g. for diesel, gasoline, etc.

  The third indicator (MJ/passenger-km) takes in addition into account changes in the average occupation rate of cars (for instance because of carpooling). The effect of changes in car occupancy can be calculated by comparing the trend of the two last indicators.

  As energy efficiency should preferably be measured in energy units and as there exist policies on carpooling to improve the efficiency of cars, it is recommended to use the third indicator.

  Related question

  • What is the unit consumption of road transport per car equivalent?
  • What is the definition of the stock of vehicles?
  • How is calculated the unit consumption per car equivalent?

Interpretation

• Why is consumption of electrical appliances per dwelling increasing over the last decades?

  The consumption of electrical appliances per dwelling is mainly determined by two main drivers: on the one hand, the change in the number of appliances owned per households (“equipment ownership”), that contribute to raise that consumption (“activity effect”); on the other hand, the variation in the average annual consumption per appliance (“specific consumption”), that usually contributes to reduce this consumption due to the increased efficiency of appliances (“efficiency effect”). In the last decades, the activity effect has been greater than the efficiency effect, mainly because of the spread of a variety of small appliances resulting in an overall increase in the consumption of electrical appliances per dwelling. For more information see http://www.odyssee-mure.eu/publications/efficiency-by-sector/households/energy-consumption-large-appliances-dwelling.html and http://www.indicators.odyssee-mure.eu/decomposition.html (sector household; sub-sector electrical appliances).

  Related question

  • What are the different explanatory factors of energy consumption variation in residential sector?

  
  Link to tool
• Why did the specific consumption of new cars decrease faster since 2007?

  The reduction in the specific consumption of new cars has accelerated since 2007 (- 3.7% per year compared to 1.5% between 2000 and 2007 at EU level), mainly because of EU regulations on labelling and emission standards and national fiscal policies promoting the purchase of low emission cars (see the trends at http://www.odyssee-mure.eu/publications/policy-brief/transport-efficiency-trends.html ).

Tools

• What are the reasons of the energy consumption variation between year t0 and t?

  Go to the decomposition tool http://www.indicators.odyssee-mure.eu/decomposition.html and select the country, sector (and sub sector) and period (t0,t) you are interested in.

  
  Link to tool
• What has been the impact of economic growth on the energy consumption variation?

  Go to the decomposition tool http://www.indicators.odyssee-mure.eu/decomposition.html and select the country, sector (and sub sector) and period (t0,t) you are interested in: the impact of economic growth is given by the activity effect.

  Related question

  • What are the reasons of the energy consumption variation between year t0 and t?

  
  Link to tool
• Why the primary and final energy consumption have a different variation?

  Go to the decomposition tool http://www.indicators.odyssee-mure.eu/decomposition.html and select the country, “primary” as sector and period (t0,t) you are interested in.

  
  Link to tool