Electricity has to be generated from other sources of energy, such as gas, oil,
nuclear, wind and solar, all of which have different levels of CO2 emissions.
The total amount of CO2 emitted is therefore a product of both the amount of electricity produced to meet demand,
and the sources used for it's generation.
If we can shift demand to times when the contributon from low CO2 sources is greatest,
we can reduce the overall CO2 emissions from electricity generation.
The purpose of this site is to provide
you with the information you need to be able to make informed choices about CO2 emissions and
how and when you use mains electricity.
Over half of UK electricity generation in 2019 came from low-carbon sources. Renewables, which produce near zero marginal emissions, represent an ever growing share, reaching 37% in 2019, an increase of 3.8% over 2018.
| Source | Production TWh | % of Total Production | Emissions Rate gCO2/KWh | Tonnes of CO2 Produced (millions) | % of Total CO2 Produced |
|---|---|---|---|---|---|
| Gas | 130.1 | 39.6 | 394 | 51 | 70.6 |
| Wind | 64.1 | 19.6 | 0 | 0 | 0 |
| Nuclear | 51.0 | 15.6 | 0 | 0 | 0 |
| Biofuels | 31.0 | 9.4 | 102 | 3 | 4.4 |
| Imports | 21.2 | 6.5 | 450 | 10 | 13.1 |
| Solar | 12.7 | 3.9 | 0 | 0 | 0 |
| Coal | 6.5 | 2.0 | 937 | 6 | 8.4 |
| Hydro | 5.6 | 1.7 | 0 | 0 | 0 |
| Other | 5.5 | 1.7 | 300 | 2 | 2.3 |
| Oil | 0.9 | 0.3 | 935 | 1 | 1.1 |
Wind, and to a lesser extent solar, make up a significant proportion of the renewable sources. These are highly dependent on both the weather and time of day and can therefore vary considerably in their overall contribution at any point in time.
As you might expect, the pattern of overall demand is a little more predictable. Higher overall during the winter than the summer, higher during the working week when offices and factories are open than at the weekend, and lowest overnight when most people are asleep and businesses are closed.
The rate at which CO2 is produced is a combination of both the amount of electicity that is being produced and
the mix of electricity generation sources used to produce it.
The chart below shows a typical week from June last year.
The blue line shows the overall demand for electricity, and the green and yellow shaded areas show the contibution to
meeting this demand that came from wind and solar power respectively. The red dashed line then shows the emissions rate
for CO2 used to generate this demand.
You can see that the overall emissions level follows the overall demand, but it is also strongly influenced by the amount of renewable energy available.
The next chart takes a close look at Monday's values from the chart above. This time the emissions rate, the total emissions divided by the total demand (black dashed line), is plotted instead of the total emissions. In this case, the rate varies from less than 180 g/KWh in the early morning to over 260 g/KWh late evening. There is also a period between 10:00 and 14:00 when the emissions are their lowest for the working day.
You can now readily see that if you minimise your use of electricty when the rate is high, and only use it when the rate is low, it is possible to make significant reductions in your own CO2 emissions.
To help do this, it would be useful to have have both a forecast for the emissions rate for the next few days, so you can plan when to use mains electricity, and some suggested approaches as to how you might use this forecast.