Impact of Climate Change on Commercial and Residential Building Energy Consumption

Climate change will have an impact on building energy consumption by altering space cooling/heating demands. A number of approaches have been employed to study the impacts of climate change on building energy consumption in the United States, including regression modeling, individual building energy simulation, and regional/national energy modeling. The research results, however, are difficult to compare and derive general conclusions from due to differences in study location, the time period considered, climate model used, emissions scenario considered, and energy type and form used. Furthermore, the robustness of the results is unclear without testing for statistical significance. We will present the results of an investigation into the impact of climate change on commercial and residential building energy consumption in the United States that attempts to overcome these limitations. We optimize the "balance point" temperature (rarely done in previous research) used to calculate degree days for each state, develop regression models for natural gas and electricity separately, and estimate the monthly/annual energy consumption change in four future periods (2030s , 2050s, 2070s, and 2090s) [1] using 15 climate models under the IPCC A2, A1B, and B1 emission scenarios. Finally, we test the significance of these results and compare them with the results derived from commonly-used 65 °F balance point temperature.

Electricity consumption increases under higher cooling demand, and natural gas consumption decreases under lower heating demand in all simulated future time periods and emission scenarios (Table 1). The increased electricity demand and decreased natural gas demand both become more pronounced over time. Because the reduction in site [2] heating fuel (including natural gas, distillate fuel oil, propane, kerosene, and wood) outweighs the increase in site electricity, total site energy consumption decreases in all future periods and the magnitude of the decrease becomes more dramatic with time. By contrast, the change in total source energy consumption is small due to the high source-to-site ratio of electricity, which together with the increase of electricity consumption offsets the large reduction in heating fuel consumption. Although the annual relative change in total source energy consumption is small, the monthly relative changes exceed ±10% in summer (Jun-July-Aug-Sep) and winter (Dec-Jan-Feb-Mar) seasons in 2090s. The small annual relative change in source energy consumption results from the cancellation of large summer increases and large winter decreases. This alteration in future annual source energy consumption also displays strong spatial variation. The net annual source energy demand increases in the warmer (southerly) states (e.g. 10% increase in Florida) due to the relative dominance of cooling needs, and decreases in colder (northerly) states (e.g. 11% decrease in Washington) due to the relative dominance of heating needs.

The above results utilize an observationally driven state-specific balance point temperature (SBP). We test the importance of optimizing a balance point temperature by comparing these results to the use of a single balance point temperature of 65 °F, a value commonly used in similar studies. The results derived from SBP are referred to as R^SBP , and the results based on 65 °F are referred to as R⁶⁵. The state annual relative differences of source energy in R⁶⁵ are usually larger than the corresponding values in R^SBP for the states with SBP lower than 65 °F (e.g. Washington), and smaller than the corresponding values in R^SBP for the states with SBP higher than 65 °F (e.g. Florida). Because SBPs are lower than 65 °F for most states, the national annual relative differences in R⁶⁵ are larger than the corresponding values in R^SBP. The state-level significance test for relative differences of source energy consumption in the 2090s shows that the medians are statistically significant for 44, 42, and 43 states in R^SBP under A2, A1B, and B1 emission scenarios respectively. Correspondingly, there are only 43, 40, and 37 significant values in R⁶⁵. The national-level significance test for relative differences of total source energy in four future periods under three emission scenarios shows that 6 of the 12 medians are significant in R^SBP, but no value is significant in R⁶⁵. The above comparison between R⁶⁵ and R^SBP suggests that the results in R⁶⁵ are less robust than R^SBP, and the use of R⁶⁵ may cause bias at the state and national levels.

Table 1. Median national annual difference (Trillion Btu) and relative difference (%, inside the parenthesis) of energy consumption relative to 2010 and significance (p <0.01 "**", 0.01≤p≤0.05 "*")

Time Period	Emission Scenarios	Site Electricity	Source Electricity	Site Natural Gas	Source Natural Gas	Total Site Energy	Total Source Energy
2030s (2020-2039)	A2	89(0.9)**	289(1)**	-261(-3.2)**	-273(-3.2)**	-201(-1)**	29(0.1)
	A1B	90(1)**	288(1)**	-351(-4.3)**	-367(-4.3)**	-369(-1.9)**	-118(-0.3)*
	B1	66(0.7)**	220(0.7)**	-200(-2.5)**	-210(-2.5)**	-198(-1)**	-80(-0.2)
2050s (2040-2059)	A2	187(2)**	608(2)**	-649(-8)**	-679(-8)**	-681(-3.4)**	-299(-0.7)*
	A1B	212(2.2)**	687(2.3)**	-713(-8.8)**	-746(-8.8)**	-640(-3.2)**	-225(-0.6)
	B1	130(1.4)**	426(1.4)**	-419(-5.2)**	-439(-5.2)**	-424(-2.1)**	-197(-0.5)
2070s (2060-2079)	A2	372(3.9)**	1195(4)**	-1141(-14.1)**	-1195(-14.1)**	-925(-4.7)**	-302(-0.7)
	A1B	316(3.3)**	1033(3.5)**	-1029(-12.7)**	-1077(-12.7)**	-966(-4.9)**	-203(-0.5)**
	B1	226(2.4)**	741(2.5)**	-734(-9)**	-769(-9)**	-766(-3.9)**	-346(-0.9)**
2090s (2080-2099)	A2	579(6.1)**	1882(6.3)**	-1585(-19.5)**	-1659(-19.5)**	-1389(-7)**	-188(-0.5)
	A1B	442(4.7)**	1426(4.8)**	-1457(-18)**	-1526(-18)**	-1256(-6.4)**	-387(-1)**
	B1	245(2.6)**	803(2.7)**	-785(-9.7)**	-821(-9.7)**	-841(-4.3)**	-478(-1.2)**

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[1] Each future period represents 20-year range. 2030s represents 2020-2039, 2050s represents 2040-2059, 2070s represents 2060-2079, and 2090s represents 2080-2099.

[2] Site energy is the final energy consumed in a building, while source energy represents the total raw energy required to provide the site energy in the building. Source energy accounts for the energy losses during production, transmission, and delivery. Source-to-site ratios are used to convert site energy consumption to source energy consumption.