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Supply Source

Supply Source

CSO statistical release, , 11am

The electricity supply data in this release is provided at hourly granularity for 2025, this includes information about net trade in electricity, the amount of electricity generated, including the primary fuel for generation, and the capture and release of stored electricity. 

The data are available at monthly, daily and hourly intervals. (See PX-Stat tables ESSA01, ESSA02, ESSA04).

Monthly Supply Source

Renewable electricity generation typically makes up a larger percentage of electrical supply during the winter months compared to the summer months (See Figure 2.1). This is largely due to higher mean wind speeds in winter, with a correspondingly higher generation of electricity from wind.

December had the highest average daily electricity supply to the grid at 108 GWh, with 17% being imported, 37% coming from non-renewable generation, and 45% being generated from renewables. 

May had the lowest average daily electricity supply to the grid at 90 GWh, 83% of the December amount. 22% of this electricity was imported, 43% came from non-renewable generation, and 33% was renewable.

Net ImportsStorageGeneration Non-RenewableGeneration Renewable
January11.41.151.443.2
February12.8133.860.4
March18.30.941.140.8
April15.7143.234.4
May20.11.338.629.7
June21.11.132.735.6
July14.11.144.730.6
August17.51.138.632.8
September18.21.233.241.1
October16.21.137.544.8
November17.81.243.344.9
December17.91.24048.9
Table 2.1 Average Daily Electricity Supply Source by Month 2025

Daily Electricity Generation Source

There can be large variations in the share of electricity generated from renewable sources on a daily basis (See Figure 2.2). Note that the figures here only refer to generated electricity, not total supply. In 2025, the highest share of electricity generation from renewable sources, was 86% on 23 February, the lowest share was 11% on 20 January, the difference was largely caused by changes in generation from wind.

Figure 2.2: Daily Percentage Share of Electricity Generation from Renewables and Non-Renewables 2025

Hourly Electricity Supply Source

The following charts give examples of the hourly electricity supply profile on two different days, one with a high share of renewable energy, the other with a low share of renewable energy.  

There was a high renewable share on the 20th of February, with 85% of electricity generation coming from renewable generation. Most of the electricity and almost all of the renewable generation came from wind, with most non-renewable generation coming from gas. 

Electricity storage and some electricity imports were used to meet the peak time demand in the evening, mainly between 4pm and 10pm.

Figure 2.3: Hourly Electricity Supply by source on 20 February 2025

There was a low renewable share on the 21st of August, with only 14% of the electricity generation being renewable, making up 10% of the total electricity supplied on the day. Most of the electricity came from gas. Notably, there was very little wind generation on this day. There was some solar generation during the daytime hours, significantly more than during the winter months.

Figure 2.4: Hourly Electricity Supply by source on 21 August 2025