Conclusion

The very warm weather over the last few weeks has disguised the problems of fuel poverty in the UK. Using data on house internal temperatures from Switchee, I forecast that In the coldest weeks of this winter almost 30% of social tenants in the UK will keep their homes below 18 degrees every hour of the day. This implies that well over 1m social homes will be too cold. Two years ago, this number was about 10%, or little more than a third of the numbers expected this year. The rise in the price of energy will cause a substantial rise in illnesses brought on by cold housing. The low internal temperatures will also bring about an increase in important problems such as interior mould.

The method used to predict excessively cold homes

The detailed information to support my conclusion is provided by Switchee, the UK’s leading ‘Internet of things’ platform for social housing. Switchee’s thermostats provide data to the landlord which shares it (suitably anonymised) with Switchee. It is then aggregated.

The database is richly informative. It can be used to identify the number of households that hold the temperature of the house below any particular temperature. As might be expected, as the outside temperature falls, the number of homes not ever heated to an adequate 18 degrees rises sharply. As the later charts in this article show there is a clear linear relationship between the external temperature and the percentage of homes that are kept cold. We can use this robust relationship to forecast what we can expect for the 2022/23 heating season.

What previous years have shown us

The chart below shows the percentage of homes never reaching an internal temperature of 18 degrees during rolling 7 day periods in the last four years.[1] These houses were cold every minute of an entire week. As would be expected, the share of cold homes peaks in winter, although homes were also cold during the snaps of chilly weather in April 2022, a time when gas prices had just been increased.

When external temperatures are low, the gas consumption necessary to keep the home above 18 degrees will be higher than at warmer winter temperatures. As prices rise, it is therefore inevitable that budget conscious customers will tend to reduce gas use, and home temperatures will fall as a result.

Chart 1

The percentage of homes never reaching 18 degrees over seven day rolling periods in the last four years

It is evident from the chart that higher gas prices in 2021/22 had begun to increase the percentage of homes unwilling to ever let the internal temperature rise above 18 degrees. Has the increase in ‘fuel poverty’ continued into the 2022/23 heating season? It may be too early to tell although the final day of 2022 data on this chart (for November 8th) shows that over 10% of homes had ceased to keep their temperature above 18 degrees over the whole of the previous 7 day period. So although the temperatures were relatively warm outside, more people were living in a cold home than at any point - even deep winter – in 2019/20.

A closer examination of the data for October and early November 2022, and a comparison with the same days in 2021, allows us to show some of the impact of the recent price rises.

Chart 2

Percentage of homes not reaching 18 degrees at any point during a single day: Comparison of September-early November 2021 and 2022

The blue columns in Chart 2 show the percentage of homes never reaching a temperature of 18 degrees each day in September, October and early November 2022. This chart does not use rolling seven day averages but measures single days. So, for example, on 27th September 2022 just over 15% of homes did not hit 18 degrees at any point in the day.

The red line marks the figure for each of the equivalent days in 2021. As we’d expect, the numbers are much lower in 2021. On 27th September 2021, the percentage not reaching 18 degrees was barely above zero.

On some days in this two month comparison, the 2021 red line rises above the blue column, particularly in late October. Unsurprisingly, the reason is probably that external temperatures were typically much lower in 2021. For example, the average for the last week of October 2021 was just 11.77 degrees, compared to 14.78 in 2022.[2]

So although it looks as though fuel price pressure may have added to the numbers of householders choosing not to heat their home. But this conclusion is muddied by the variations in temperatures between years.

The best way of assessing the impact of higher utility prices is to plot the relationship between the weekly average temperatures and the percentage of homeowners holding temperatures below 18 degrees. This analysis shows the very close link between lower temperatures and high percentages of unheated (or under-heated) homes. And, as must be expected, the position this year is far worse than in previous periods.

The Switchee database runs from September 2019 to today. The first chart shows the relationship between the average external temperature of each rolling week from September 2019 to June 2020 on the x axis and the percentage of homes not reaching 18 degrees at any stage in that seven day period. When the average temperature rises above 15 degrees, the number of homes not reaching 18 falls to about zero and these weeks are omitted from the chart (and all succeeding ones).

Chart 3

This chart shows the close relation between external temperatures and the percentage of homes never reaching 18 during the rolling 7 day period . The trend llne calculated shows that if the average external temperature was 10 degrees the percentage of homes never reaching 18 degrees in that week was about 3.6%.

July 2020 to June 2021 shows a very similar pattern. This year had some far colder 7 day periods, including some periods below zero for the 7 day rolling window.

Chart 4

As can be seen from the trendline on the chart, external temperatures below zero are associated with over 11% of homes consistently staying below 18 degrees in this one year period.

The pattern begins to change during the following year (July 2021 to June 2022). Gas prices began to increase in September 2021 but the effect was small until the end of March 2022, when the domestic price increased again, this time sharply.

Chart 4 shows that a 10 degree average external temperature in the July 2021 to March 2022 period was associated with approximately 4% of households keeping their temperature below 18 degrees. This is very little different to the previous years in the Switchee database.

Chart 5

In this period, a 7 day average external temperature of 10 degrees is associated with about 4 percent of homes never exceeding 18 degrees internal temperature. An average temperature of 0 degrees (which was not reached in this period) is predicted to cause about 11.5% of homes never heating the house to 18 degrees.

As chart 6 shows, the period from the end of March to the last days of June 2022 showed a sharp increase in householders keeping their homes cold.

Chart 6

In this short period, the percentage of homes consistently not being heated to 18 degrees when the external temperature averages 10 degrees was between seven and eight percent, almost double the figure in the first nine months of the year. The trend line on the chart suggests that were the temperature to fall to zero the percentage of cold homes would be over 21%, once again almost double the figure for the previous period.

Not unexpectedly, the continued rise in prices in the second half of 2022 has pushed even more homes into keeping the internal temperature below 18 degrees.

Chart 7

Temperatures in this last period have generally been warm. So we cannot directly see what percentage of homes will be under-heated in the coming winter. But we can predict what the likely levels will be. In previous years, the trend line has been straight and there is little reason to believe winter 2022 will be different. As temperatures fall, the number of tenants never heating their house to more than 18 degrees rises proportionately.

The figures for summer and early autumn 2022 suggest that the share of social homes kept below 18 degrees internally when the external temperature is 10 degrees will be just below 10 percent, up from 7- 8 percent in the April to June season of 2022 and no more than 3-4 percent in previous years. If the temperatures fall to an average of zero for a seven day period - which doesn’t happen every year - the trend line suggests that about 29% of all social housing tenants will be keeping their homes below 18 degrees. This figure is almost three times the level of less than two years ago.

To repeat an earlier point; keeping the house below 18 degrees is both bad for human health and also causes deterioration of the property. Mould is probable, and other damage very possible. The UK has about 4.5 million social housing homes and this analysis suggests that well over 1 million of them will be insufficiently warm in the months to come. Of course, many privately-owned homes will also be kept cold to save money. The consequences for many of the occupants will be severe.

Disclosure: I own shares in Switchee

[1] A ‘rolling seven day period’ is covers the day under study and the six preceding days. The chart therefore has 365 records per year.

[2] This figure is an average calculated across the 24 hour day and representative of the UK as a whole.