Electricity

Electricity generated

On the left hand side are the fuel inputs to electricity generation. On the right hand side are the amounts of electricity generated by each of the fuel inputs, and the total energy lost during electricity generation. Total energy inputs to electricity generation account for approximately one third of Ireland's total primary energy supply.

Generation efficiency

There is a significant difference in the shares of electricity generated by fuel compared to the fuel inputs. This is due to the different efficiencies of generating electricity in different processes. Generating electricity in traditional thermal power plants using coal, peat or biomass has low efficiency. Electricity generated from wind and hydro is 100% efficient.

A significant portion of the energy used to generate electricity is lost before the electricity reaches the final end-user, through a combination of transformation losses, own use of electricity by power plants, pumped hydro storage losses and transmission losses.

The graph shows the trends in primary energy supply for electricity generation broken-out by fuel type and energy source.

Note that non-combustible renewable sources accounted for a higher share of generated electricity than of primary energy supply for electricity generation.  This is because the thermal generation of electricity from natural gas and coal has significant energy losses, while electricity generation from non-combustible renewable sources (wind, hydro and solar) is considered to be 100% efficient.

Efficiency of electricity supply is defined as the ratio of final energy use of electricity and primary energy supply for the generation of electricity[1].

The overall efficiency is determined by the weighted average of electricity generation from non-combustible renewable sources, such as wind, hydro, and solar (taken to be 100% efficient), and electricity from combustible sources, such as gas, coal, and biomass (which have transformation losses). The efficiency of electricity supply therefore increases as the share of non-combustible renewable sources, and as more efficient fuels and technologies are employed in thermal generation plants.

The efficiency of Ireland's electricity supply has generally improved over the last decades, due to the introduction of higher efficiency natural gas plants, the closure of older peat-fired stations, and increased direct generation from renewable sources.

[1] Electricity supply efficiency includes energy consumed by electricity generating plants themselves as well as transmission and distribution losses. Electricity generation efficiency ignores these losses, hence generation efficiency is higher than supply efficiency.

The above chart details the generated electricity available for final consumption by end users, broken out by fuel type and energy source.

Higher efficiency

In conventional thermal electricity generation, we typically lose 60% of the energy input as waste heat. Combined Heat and Power (CHP) systems use this valuable heat energy to generate both useful heat and electricity from a single combustion process. CHP plant efficiency is usually 20% to 25% higher than heat-only boilers and conventional power stations combined. Also, these plants are physically closer to the users of their generated heat and electricity, for example at hotels or factories.

Combined heat and power also avoids some of the transmission losses incurred by centralised generation.

See the download below for more information on CHP in Ireland.

• CHP in Ireland 2020 update

Trend in electricity CO₂ intensity

This chart shows the CO₂ emission intensity of Ireland's electricity supply, which is measured in gCO₂/kWh. The stacked bars show the share of CO₂ emissions by fuel for each kWh of electricity supplied in Ireland. It is important to note that the stacked bars in the graph represent the contributions of different fuels to the overall CO₂ intensity of Ireland's electricity supply, not the CO₂ intensity of the individual fuels themselves.

The CO₂ intensity of electricity generation fell to a historic low in 2020, before increasing slightly in 2021 due to an increase in emissions from coal and, to a lesser extent, oil. The CO₂ intensity fell again in 2022, due to a decrease in the share of oil and coal in the generation mix. The dramatic overall improvements in annual CO₂ emission intensity are due to reductions in using coal for electricity generation, and increased generation from zero-carbon renewable sources.