When we look at the data, the highest demand for electricity comes between 6pm and 6.30pm when more people are at home and cooking dinners, watching TV or using other devices that require a plug. The electricity demand generated during this 30-minute period is at its highest in January - reflecting the colder weather and less daylight - and at its lowest in June with its longer and warmer evenings.

To meet this demand, the electricity source also changes and in January 2023, 42% of the electricity needed during this 30-minute peak came from renewables, with the majority of this renewable contribution coming from wind power. However, for the same 30-minute peak in June, only 30% of the electricity came from renewables, with wind power being a smaller proportion of the renewable contribution as there was less wind generated in milder conditions.

Generally, the proportion of renewable fuels varies throughout the day and a higher proportion of fossil fuels – mainly gas - is required to meet peak electricity demand in the evening. For the peak 6-6.30pm period in January, 45% of the electricity generated came from gas and for the same period in June, it was 59%.

At these peak times, all available generation sources are generally operating and you will also see the use of hydro stations on our rivers such as Ardnacrusha on the Shannon and pumped hydro facilities such as Turlough Hill in Co Wicklow.

When demand peaks, so too does cost. This means that using your washing machine or dryer during peak morning or evening hours will cost you more in you bill if you are on a variable rate plan. Electricity prices are at their lowest overnight reflecting the lower demand and given the significant increases in electricity bills in recent years, this is valuable information. Having this information allows us make choices, not just on how much electricity we use but also on when we use it. For example, owners of electric cars may choose to charge their batteries overnight, rather than during the day.

Over the past 20 years, there has been a significant evolution in the use of renewables for electricity generation.  In 2005, only 2% of our electricity was generated from wind, while today, natural gas and wind dominate the generation of electricity in Ireland.  In 2023, 47% of our metered electricity came from gas and 39% from wind.  It is worth noting, however, that they often move in opposite directions so that on days where a high proportion of electricity is generated from wind, there is a decrease in the amount generated from gas.  The converse is also true in that when the wind is not blowing, most of our electricity is generated from gas.

Over the past 20 years, Ireland has been phasing out the burning of peat for electricity generation as well as reducing our use of coal.  According to the Environmental Protection Agency (EPA), the carbon intensity of our energy is falling and in 2022 the emissions associated with energy industries fell, which was driven by reductions in the amount of coal, oil, and peat used in electricity generation. Indeed, in 2022 emissions associated with energy decreased by 1.8%. This reflects a general trend where increased use of renewables reduced the carbon intensity of our electricity.  This finding is balanced, however, by the fact that we are still using fossil fuels for more than half of our electricity generation, in particular at peak times, as our figures for electricity generation for 2023 showed.

Metered electricity generated from solar farms, while small, is growing and it accounted for 1.5% of our electricity generation in 2023. Indeed, the half-hourly period with the highest amount of metered electricity generated from solar farms occurred between 2pm and 2.30pm in May. These figures exclude electricity generated by households and businesses from rooftop panels which are primarily for their own consumption.

Taken together, this data shows our electricity generation is a complex system that balances uneven demand and varied generation sources. It is also evolving to meet the needs of a growing population and economy. The CSO will continue to publish this information monthly giving us all additional insights into how our electricity generation system works, what the source of that electricity is, to help us all make decisions that reduce our impact on the climate and our electricity bills. The CSO also has a sister publication on electricity consumption which provides detailed insights for households and businesses.