6.5.1 Recent advances in potential estimations from around the world

Chapter 3 of the TAR (IPCC, 2001) provided an overview of the global GHG emission reduction potential for the residential and commercial sectors, based on the work of IPCC (1996) and Brown et al. (1998). An update of this assessment has been conducted for this report, based on a review of 80 recent studies from 36 countries and 11 country groups, spanning all inhabited continents. While the current appraisal concentrates on new results since the TAR, a few older studies were also revisited if no recent study was located to represent a geopolitical region in order to provide more complete global coverage. Table 6.2 reviews the findings of a selection of major studies on CO₂ mitigation potential from various countries around the world that could be characterized in a common framework. Since the studies apply a variety of assumptions and analytical methods, these results should be compared with caution (see the notes for each row, for methodological aspects of such a comparison exercise).

According to Table 6.2, estimates of technical potential range from 18% of baseline CO₂ emissions in Pakistan (Asian Development Bank, 1998) where only a limited number of options were considered, to 54% in 2010^[9] in a Greek study (Mirasgedis et al., 2004) that covered a very comprehensive range of measures in the residential sector. The estimates of economic potential^[10] vary from 12% in EU-15 in 2010^[11] (Joosen and Blok, 2001) to 52% in Ecuador in 2030^[12] (FEDEMA, 1999). Estimates of market potential^[13] range from 14% in Croatia, focusing on four options only (UNFCCC NC1 of Croatia, 2001), to 37% in the USA, where a wide range of policies were appraised (Koomey et al., 2001).

Table 6.2: Carbon dioxide emissions reduction potential for residential commercial sectors

Table 6.2b.

Table 6.2c.

Notes specify those parameters which are different from those identified below (the number of a note is the number of the model parameter):

a) Hungary, Slovakia, Slovenia, Estonia, Latvia, Lithuania, Poland and the Czech Republic

1. Discount Rate (DR) belongs to the interval [3%; 10%]. 2. Most models are Bottom-up (BU). 3. All models consider CO₂. If a study considered GHGs, CO₂ only was analysed, if the study assessed C, potential was converted into CO₂. 4. Baseline (BL) is Business-as-Usual Scenario (BAU) or similar (Frozen efficiency scenario is abbreviated as fr-ef). 5. Base year (BY) is 2000; Target year (TY) is 2020. 6. Costs covered: cost of incremental reduction, abatement costs, costs of avoided or saved or mitigated CO₂, marginal costs. 7. Estimations are made for Residential (R) and commercial (C) sectors in sum.

Our calculations based on the results of the reviewed studies (see Box 6.1) suggest that, globally, approximately 29% of the projected baseline emissions by 2020^[14] can be avoided cost-effectively through mitigation measures in the residential and commercial sectors (high agreement, much evidence). Additionally at least 3% of baseline emissions can be avoided at costs up to 20 US$/tCO₂ and 4% more if costs up to 100 US$/tCO₂ are considered. Although due to the large opportunities at low-costs, the high-cost potential has been assessed to a limited extent and thus this figure is an underestimate (high agreement, much evidence). These estimates represent a reduction of approximately 3.2, 3.6 and 4.0 billion tonnes of CO₂-eq in 2020, at zero, 20 US$/tCO₂ and 100 US$/tCO₂, respectively. Due to the limited number of demand-side end-use efficiency options considered by the studies, the omission of non-technological options, the often significant co-benefits, as well as the exclusion of advanced integrated highly efficiency buildings, the real potential is likely to be higher (high agreement, low evidence). While occupant behaviour, culture and consumer choice as well as use of technologies are also major determinants of energy consumption in buildings and play a fundamental role in determining CO₂ emissions, the potential reduction through non-technological options is not assessed. These figures are very similar to those reported in the TAR for 2020, indicating the dynamics of GHG reduction opportunities. As previous estimates of additional energy efficiency and GHG reduction potential begin to be captured in a new baseline, they tend to be replaced by the identification of new energy-efficiency and GHG-mitigation options. For comparison with other sectors these potentials have been extrapolated to 2030. The robustness of these figures is significantly lower than those for 2020 due to the lack of research for this year. The extrapolation of the potentials to the year 2030 suggests that, globally, at least 31% of the projected baseline emissions can be mitigated cost-effectively by 2030 in the buildings sector. Additionally at least 4% of baseline emissions can be avoided at costs up to 20 US$/tCO₂ and 5% more at costs up to 100 US$/tCO₂ (medium agreement, low evidence)^[15]. This mitigation potential would result in a reduction of approximately 4.5, 5.0 and 5.6 billion tonnes of CO₂-eq at zero, 20 US$/tCO₂ and 100 US$/tCO₂, respectively, in 2030. Both for 2020 and 2030, low-cost potentials are highest in the building sector from all sectors assessed in this report (see Table 11.3). The outlook to the long-term future assuming options in the building sector with a cost up to 25 US$/tCO₂ identifies the potential of approximately 7.7 billion tonnes of CO₂ in 2050 (IEA, 2006d).

The literature on future non-CO₂ emissions and potentials for their mitigation have been recently reviewed in the IPCC/TEAP report (2005). The report identifies that there are opportunities to reduce direct emissions significantly through the global application of best practices and recovery methods, with a reduction potential of about 665 million tonnes of CO₂-eq of direct emissions in 2015, as compared to the BAU scenario. About 40% of this potential is attributed to HFC emission reduction covered by the Kyoto Protocol to the UNFCCC, while HCFCs and CFCs regulated by the Montreal Protocol contribute about 60% of the potential. A key factor determining whether this potential will be realized is the costs associated with the implementation of the measures to achieve the emission reduction. These vary considerably from a net benefit to 300 US$/tCO₂-eq. Refrigeration applications and stationary and mobile air conditioning contribute most to global direct GHG emissions. Action in these sub-sectors could therefore have a substantial influence on future emissions of HCFCs and HFCs. The available literature does not contain reliable estimates for non-CO₂ mitigation potentials in the long-term future, including the year 2030. Therefore, the 2015 figures can serve as low estimates of the potentials in 2030, taking into account that upcoming progressive policies in many countries have already led to new products with very low non-CO₂ emissions as compared to their previous analogues.