5 things you didn't know about where your electricity comes from

Analysis: Knowing how the electricity we use in our homes and businesses was generated is valuable information when it comes to cost and demand

When we flick a light switch, put on a kettle or charge our phone, few of us think about how the electricity we use is generated. Understandably, electricity generation is rarely at the front of your mind but given the challenges of climate change, the cost of living and energy security, knowing whether your electricity has been generated by renewable energy, such as wind, solar or hydro power, or by fossil fuels is vitally important.

Until now, there has not been a full picture of our electricity generation sources by time of day, but the Central Statistics Office (CSO) recently published figures showing where our electricity comes from at half hour intervals for all of 2023. Deirdre Mahony is Assistant Director General at the CSO with responsibility for Climate, Environment, Enterprise & Sustainability and she tells us about how we’re powering the country.

Why is this information so important?

"Decisions made by individuals on when to put on a dryer or by companies on the energy efficiency of their work, all contribute to the amount of electricity we need to generate. Matching demand with supply is a complex process and few people realise that the time of year and even the time of the day or night that you use electricity affects the source of that electricity."

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Many people may just think about the cost of the bill so are demand and cost related?

"Generally, 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 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 all to make choices, not just on how much electricity we use, but also when we use it. For example, owners of electric cars may choose to charge their batteries overnight, rather than during the day to take advantage of the cheaper rates."

When does demand peak and how do we generate the electricity to meet it?

"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 sources change. For instance, 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.

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"While demand peaks at the same time each day, how we meet that demand changes. Generally, the proportion of renewable fuels varies throughout the day and so 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 2023, 45% of the electricity generated came from gas and for the same period in June 2023, 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."

How have our sources of electricity changed over time?

"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 our 2023 figures show 38.9% of our electricity coming from wind. Natural gas accounted for 47.2% of our electricity generation in 2023.

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"But it is worth noting that they often move in opposite directions. 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 natural gas.

"We’re also seeing an increase in solar generation with metered electricity generated from solar farms, while small, accounting for 1.5% of our metered electricity generation last year. 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 solar panels which are primarily for their own consumption."

What do these changing sources mean in terms of carbon emissions?

"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 has been falling. The emissions associated with energy industries in 2022 fell by 1.8%, driven by reductions in the amount of coal, oil and peat used in electricity generation.

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"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."

Will the CSO continue to publish this information in the future?

"The CSO will continue to publish this information giving us all additional insights into how our electricity generation system works 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, businesses, and data centres."

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The views expressed here are those of the author and do not represent or reflect the views of RTÉ