13. Supply of Gas to Households
JP Palutikof

Domestic gas use in the UK in January-March (first quarter) as a percentage of annual total gas use shown in relation to January-March temperatures in Central England (dashed line).

Specific indicator
In recent decades, there has been a pronounced increase in energy consumption in the home in the UK and a shift towards gas at the expense of other fuels. To remove this trend and to reveal the fluctuations in gas use due to changes in winter weather, the specific indicator chosen is the proportion of UK annual domestic gas supply consumed in winter.
[Source: Energy Trends, available from Department of Trade and Industry, 1 Victoria St., London SW1H 0ET]

Relevance
Domestic energy use increased by about 30% between 1970 and 1996. In 1996, gas directly fulfilled 67% of the domestic energy requirement, compared to only 31% in 1972. The gas industry has, therefore, captured an increasing share of a growing market. Domestic consumers are the largest users of natural gas, taking over 40% of total output.

In 1996, purchases of fuel and power accounted for 4.3% of total household expenditure, and total consumer spending on energy products amounted to £377 billion. Mild winter weather can produce considerable savings in consumer expenditure on energy. For example, it is estimated that the mild winter of 1994/5 led to savings of £220 million in UK domestic gas consumption.

Sensitivity to climatic and other factors
Domestic energy use is dominated by space heating, which consumes 62% of the total, and is strongly weather sensitive. The remaining 38% is mainly for water heating and cooking, and is relatively insensitive to weather conditions. The space heating requirement creates a strong seasonal cycle in domestic energy use: during the 1990s, sales in the winter quarter (January - March) have averaged around four times sales in the summer quarter (July - September). Superimposed on this seasonal cycle, there are fluctuations in consumption in response to unusually warm or unusually cool conditions. As might be expected, these weather-energy use relationships are strongest in the winter quarter.

Relative pricing structures for domestic fuels over the last three decades have favoured widespread adoption of gas at the expense of electricity, oil and solid fuels. This has created a long-term upward trend in gas consumption, from around 400 TeraWatt hours in the winter quarters of the early 1970s, to around 1400 TeraWatt hours per winter quarter at present. Today, some 88% of households have central heating, compared with under 40% in the early 1970s. This indicator should therefore have become more sensitive to weather fluctuations over the period of record.

Since space heating requirements greatly increase domestic gas consumption in the coldest months of the year, winter temperatures are likely to correlate strongly with winter gas use. Statistics of gas sales are produced at quarterly intervals, the first quarter figure including the months January - March. There is a strong inverse relationship between domestic gas use (expressed as a proportion of total annual use) and average central England temperature over the first three months of the year.

Change over time
Years with cold winters, including 1979, 1985-87, 1996 and to a lesser extent 2001, show relatively high gas consumption in the winter quarter. As expected, in more recent years gas consumption appears to display a greater sensitivity to temperature. Thus, the coldest first quarter in the series was in 1979, when the average temperature was 1.8oC and gas use was 42% of the annual total. In 1996 the winter-quarter temperature was 3.8oC but gas use was 43% of the annual total.

The winter quarter of 1996 was the fifth coldest in the record, and produced the third highest gas use figures. Since then, January - March temperatures have been warmer than average in five of the six years up to 2002, and gas consumption has in consequence been unusually low. The exception, 2001, was relatively cool at 4.3oC, and hence gas consumption rose.

The winter season will always produce the lowest temperatures and the highest use of domestic space heating. With or without the higher temperatures predicted by global warming, the relative seasonal differences in space heating requirements are likely to be maintained at similar levels to those of today. Thus, winter gas use, as a proportion of annual use, will reflect temperature variability as it has done in the past. So long as gas retains its present space-heating role (which depends on energy pricing structures) the sensitivity of the series is not expected to change substantially.