How the 2021 summer heat dome affected electricity demand in western Canada

This article was published by the Canada Energy Regulator on Nov. 17, 2021.

From late June to early July 2021, a warm weather event, known as a heat dome, settled over western Canada and the northwestern United States.^Footnote1 The rise in temperatures associated with this event led to increased electricity demand in Alberta and British Columbia (B.C.), which was noticeably higher than in previous summers. This market snapshot explores the high temperatures seen during the heat dome and the effects they had on electricity demand in Alberta and B.C.

The heat dome resulted in several days of high temperatures that approached 50 degrees Celsius (°C) in Lytton, B.C., setting an all-time temperature record for Canada.^Footnote2 In other parts of B.C., temperatures peaked at 34°C in Vancouver and 40°C in Victoria on 28 June, with Kamloops reaching 47°C a day later. Albertan temperatures peaked at 34°C degrees in Edmonton and 36°C in Calgary on 30 June. These summer temperatures set all-time high records in interior B.C., Victoria, and Edmonton. Slightly hotter temperatures were recorded in Calgary in 1919 and 2018, and in Vancouver in 2009. The heat dome had less impact on temperatures in eastern Canada.

Figure 1: Maximum Daily Temperature in June and July for Select Cities in Alberta and B.C.

Figure 2 shows average monthly electricity use is Alberta and B.C. from 2015 to 2020, compared to 2021. During periods of high temperatures, like those that occurred during the heat dome, people are more likely to turn on air conditioning units to cool their houses and other buildings. Air conditioners are normally powered by electricity and can create noticeable increases in electricity demand when many are used at the same time. When temperatures are low in winter, people use more heating, which typically comes from either natural gas or electricity in Alberta and B.C. Cold temperatures and long nights during winter also keep people indoors where they use more electricity for lighting or entertainment like watching TV. In homes heated with natural gas, the fans used to circulate hot air produced by furnaces also consume significant amounts of electricity.^Footnote3

Figure 2: Average Monthly Electricity Demand from 2015-2020 compared to 2021 in Alberta and B.C.

Both Alberta and B.C. tend to see their electricity demand peak between December and February before falling off during the spring and summer. Compared to previous summers, June and July of 2021 had significantly higher than normal average hourly electricity demands in both provinces. Average hourly demand in B.C. approached 7 000 megawatts (MW) for the two months, when in previous summers it was closer 6 500 MW per hour. In Alberta in July 2021 average demand came close to 10 000 MW per hour, while it was generally around 9 500 MW in previous years. Average Albertan hourly demand in June 2021 was above 9 600 MW, up from an average of 8 900 MW over the previous five years.

Despite having a smaller population than B.C., Alberta consumes significantly more electricity per year. In 2019, Alberta consumed almost 87 000 gigawatt hours (GWh) of electricity, while B.C. consumed just under 59 000 GWh.^Footnote4 This difference mainly comes from Alberta’s energy intensive industrial sector, which consumed more than twice as much electricity as B.C.’s industrial sector in 2019.

In Alberta, there is typically a relatively small number hours in a year where total electricity system demand exceeds 11 000 MW. In B.C., a comparably high demand hour would be closer to 9 000 MW. In most years, these hours occur only during the winter months of December, January, and February, when temperatures are at their coldest and heating demand is at its highest.

In the six years from 2015 to 2020, there were only 10 hours in June, July, and August where electricity demand in Alberta was above 11 000 MW, while 63 such hours occurred in the summer of 2021. All the hours where summer demand was over 11 000 MW from 2015 to 2020 occurred in August 2018 during a heatwave.^Footnote5 In B.C. there were 21 hours where demand was above 9 000 MW in June, July, and August between 2015 to 2021, all of which occurred during the 2021 heat dome.^Footnote6 So far in 2021, the heat dome has accounted for 22 per cent of high demand hours in Alberta and 5 per cent in B.C. However, this share is likely to shrink as high demand hours tend to occur in November and December in both provinces.

Figure 3: Average Daily Electricity Demand in June and July for Alberta and B.C.

If extreme temperature events like the heat dome become more common in the future, some Canadian regions may see summer peak electricity demand that approach the peaks of winter. This summer demand shift could be accelerated if more homes and businesses install air conditioning in response to hotter temperatures. Changes in seasonal demand could affect electricity grid planners, who must ensure enough electricity can be produced to meet both winter and summer peaks.

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