Trystan Lea

What might a Zero Carbon Gwynedd look like?

Published: 1st June, 2023

Updated 17th August to reflect updated Wales wide analysis.

Mae'r tudalen yma hefyd ar gael yn Cymraeg.

The following tries to answer this question by looking at Gwynedd within the context of the national ZeroCarbonBritain scenario developed by The Centre for Alternative Technology in Machynlleth. It looks at energy use in Gwynedd today, how much energy we generate from renewable energy in Gwynedd and how much we would need to build either here in Gwynedd or at a wider scale in order to supply Gwynedd's projected energy needs if we followed the ZeroCarbonBritain scenario.


The analysis here is based on the three summarised data tables below:

  1. Gwynedd energy use, carbon emissions today.
  2. Energy demand in a future Zero Carbon Gwynedd scenario
  3. Renewable energy in Gwynedd today and how much more we would need either here in Gwynedd or imported from further afield to meet our projected share of ZeroCarbonBritain energy demand.

Energy and carbon in Gwynedd today

GHG Emissions 1,093,000 tCO2e [1]
Electricity 532 GWh [2] (244 GWh domestic, ~3800 kWh/household), 35% from Gwynedd renewables *
Gas 530 GWh (364 GWh domestic) [2]
Oil 1551 GWh (262 GWh domestic heat, 1149 GWh transport) [2]
Coal 65 GWh (43 GWh domestic heat) [2]
Bioenergy 118 GWh (49 GWh domestic heat) [2]
Total final energy 2796 GWh/yr [2]
Total primary energy estimate 3808 GWh/yr *

* Electricity supply on a national average basis is currently about 21% from wind, solar and hydro, 19% from nuclear, 11% from bioenergy (of which about half comes from drax wood chip’s). The remaining 49% is mostly gas power stations, plus a little from oil and coal.

* Primary energy estimate based on 1.36x factor difference between national primary and final energy figures. This covers thermal power station losses, grid losses, other conversion losses and energy industry own use [3].

These figures give us an idea for how much energy we use today, the exact figures and units are less important than the overall relative changes. We use a lot of energy today, we can save a lot of energy just by switching to more efficient technology such as heat pumps and electric vehicles. 35% of our electricity consumption is currently generated by local renewable energy in Gwynedd but electricity is only 20% of final energy demand.

Energy demand in a future ZeroCarbonGwynedd scenario

The following is based on a proportional share (by number of households) of the national ZeroCarbonBritain scenario [2], modelled using the open source ZeroCarbonBritain scenario tool.

ZCB [3]
Lighting, Appliances and Cooking 206 GWh/yr (More efficient appliances)
Space and Water heat, fuel demand 237 GWh/yr (Retrofit & heat pumps)
Transport demand 288 GWh/yr (Electrification & modal shifts)
Industry demand 530 GWh/yr (Increased by onshoring and economic growth)
Total final energy demand 1261 GWh/yr
Losses & conversion 419 GWh/yr
Excess / curtailment 268 GWh/yr
Total primary energy supply 1948 GWh/yr
Renewable electricity supply 1434 GWh/yr
Bio-energy supply 440 GWh/yr
Geothermal & solar thermal 74 GWh/yr

Like most energy scenarios, ZeroCarbonBritain is a combination of changes on both the demand side and supply side of the energy system. It includes almost full electrification of heat and ground transport in order to make the most efficient use of zero carbon electricity. It is also particularly ambitious compared to other scenarios in reducing demand with building retrofit and behaviour change, it includes:

Total primary energy demand is reduced by almost 50% compared to our energy use today.

Other scenarios such as the recently published 100% Renewable UK scenario are much less ambitious on reducing demand and compensate by building more supply. ZeroCarbonBritain also sources a relatively large share (23%) of it's energy supply from biomass energy, this uses 18% of total UK land area. It might be better to build more wind, solar and associated power-to-gas and liquid fuels infrastructure (with carbon recycling or direct air capture) so that we can free up more land for biodiversity.

An alternative higher demand, low biomass scenario simulated using the ZeroCarbonBritain scenario tool, reflecting 2018 levels of miles travelled by car and air, would require a primary energy supply of ~2620 GWh/yr [12] and final energy demand of ~1750 GWh/yr. The electricity supply requirement would increase from 1434 GWh/yr in the base scenario to ~2560 GWh/yr. This is a similar demand level to the 100% Renewable UK scenario (scaled down to a Gwynedd proportional share).

Electrification progress

While electrification of heat, transport and industry are key parts of both the ZeroCarbonBritain and 100% Renewable scenarios we are still only at the first few % points of the transition on the demand side.

Today ZCB
Electrification of heat with heat pumps 553 projects, 6.0 MW thermal, ~1% ~40,000-60,000 projects, 90%
Electrification of transport ~2% 90%

Renewable Energy in Gwynedd today vs a future ZeroCarbonGwynedd scenario

Current (2021) ZCB [3] Progress
Renewable Electricity 186.2 GWh/yr 1434 GWh/yr 13%
Offshore Wind 0 MW 258 MW (975 GWh/yr) 0% (0%)
Onshore Wind 6.2 MW (12.8 GWh/yr) [4] 55 MW (141 GWh/yr) 11% (9%)
Solar PV 43 MW (36 GWh/yr) [4] 166 MW (137 GWh/yr) 26% (26%)
Tidal 0 37 MW (77 GWh/yr) 0% (0%)
Wave 0 18 MW (45 GWh/yr) 0% (0%)
Geo Thermal Electricity 0 5.5 MW (43.4 GWh/yr) 0% (0%)
Hydro 62.2 MW (135.4 GWh/yr) [4] 5.5 MW (14.5 GWh/yr) 1130% (933%)
Total biomass & waste 2.42 MW (2.0 GWh el/yr) [2] see biomass for biogas
Renewable Heat 48.7 GWh/yr 144 GWh/yr 34%
Geo Thermal Heat ? 3.7 MW (29 GWh/yr) 0% (0%)
Solar Thermal 168 projects, 0.5 MW thermal [6] 12.8 MW (45 GWh/yr) 4%
Biomass for direct heat 48.7 GWh/yr [2] 70 GWh/yr 70%
Renewable Fuels 54.2 GWh/yr 370 GWh/yr 15%
Biomass for biogas ~5 GWh/yr [5] 170 GWh/yr 3%
Biomass for liquid fuels 49.2 GWh/yr [2] 200 GWh/yr 25%

Additional storage infrastructure is required to provide a complete working energy system that matches demand for every hour of every day. Gwynedd's share of national storage requirements based on the ZeroCarbonBritain model would very roughly be: 370 MWh high efficiency electricity storage, 50 MW of electrolysis, 40 GWh of hydrogen storage, 120 GWh of e-methane storage, 120 MW of backup gas turbine capacity. These are indicative figures to provide a more complete picture of what the model suggests is required [3]. We do already have two large pump hydro storage schemes: Dinorwig and Ffestiniog which have a combined storage capacity of 10.5 GWh and there is another proposed project at Glyn Rhonwy.

The following chart shows the recent historic generation output from renewable energy in Gwynedd. Extrapolating a linear trend suggests 465 GWh/yr of generation in 2050 or about 32% of the ZeroCarbonBritain based scenario value. At this rate of renewable deployment (+9.5 GWh/yr), it would take ~130 years to reach 1434 GWh/yr or 250 years to reach the higher demand scenario if the goal was to meet Gwynedd energy demand from within Gwynedd.

What is the goal? Local vs national
A goal of supplying Gwynedd energy demand from zero carbon energy within the Gwynedd boundary or near offshore is itself a goal that may or may not be the right one. It is usually better to take a wider view.

Wales as a whole is moving faster with a historical renewable build rate that would suggest reaching the ZeroCarbonBritain target in ~68 years and a pipeline of large scale renewable projects that should get us there even faster (Awel y mor, Mona/Morgan, Celtic sea floating wind & Morlais). We may even get to 70-90% of the standard ZeroCarbonBritain scenario target by 2035, with the renewables that are already in the pipeline. Leaving time to get to 100% by 2050. For a ZeroCarbonBritain scenario, Wales might require an additional ~7,200 GWh/yr of electricity generation beyond the existing pipeline. A higher demand scenario might need an additional ~25,500 GWh/yr. Could Gwynedd contribute to this meeting this shortfall?

Could we find an additional 1250 - 2400 GWh/yr of generation in Gwynedd?

If we did decide that we wanted to meet Gwynedd energy demand from generation within Gwynedd or that we want to make a substantial additional contribution to meet the Wales wide need for additional generation post 2035, the following gives an idea for how we might approach this.

Risks to achieving these generation goals

Opposition to development

Grid contraints: Grid constraints are another key factor currently limiting the development of projects e.g Ynni Llyn tidal, proposals for offshore wind in Cardigan bay and onshore wind in mid wales. Some resolution to this issue will clearly be needed if we are to meet our zero carbon goals.

Other generation options

Nuclear: Trawsfynydd is of course one of the sites proposed for a 440 MW Rolls Royce Nuclear SMR, which at a capacity factor of 90% would generate 3470 GWh/yr 2.4x the ZCB renewable electricity target or 1.35x the Gwynedd higher demand scenario. On a Wales wide basis this project would take us from 87% to 99% of the lower demand target or from 53% to 61% of the high demand target. A recent report by the European Commission's Joint Research Centre highlighted that nuclear performs well on a large number of life cycle analysis metrics including a similar carbon intensity to wind [13].

There is still a lot of uncertainty around the likelihood of the Trawsfynydd project being built, given the UK Government decision to open a more competitive process for technology selection alongside pushing the final investment decision back to 2029. This suggests that the original early 2030 delivery dates are less likely. There is a big question as to how the next generation of nuclear projects will fare given past challenges, projects due for delivery before 2030 in Canada (BWRX-300) and the USA (Nuscale) should start to give a clearer indication.

CCS is another option that while less likely to be applicable in Gwynedd may play a part in a wider Wales scenario. There is a proposal to build a 350 MW Allam-Fetvedt Cycle natural gas CCS plant in Teeside that is based on an already working pilot plant in the US [11]. The technology itself is also useful for a 100% renewable scenario as it could make long duration energy storage with e-methane produced using renewable electricity more efficient.

There are other problems with these technologies and they do not yet have at least a recent history of tried and tested regular deployment in the same way that wind and solar have, suggesting caution on relying on their development at this stage. There are of course elements of 100% RE scenarios that are also at a similar early stage of development such as long duration energy storage with hydrogen or e-methane.



  1. UK local authority and regional greenhouse gas emissions national statistics, 2005 to 2020
  2. Sub-national total final energy consumption data
  3. ZeroCarbonBritain hourly energy model and scenario tool
  4. Renewable electricity by local authority, 2014 to 2021
  5. Based on 2.0 GWh el/yr [3] and 40% conversion efficiency.
  6. Energy generation in Wales 2019
  7. Energy use in Wales
  12. High demand primary energy estimate: 1312 TWh/yr national scenario modelled in ZCB tool × 55100 households 2018 ÷ 27600000 households 2018 = 2620 GWh/yr. 100% RE UK IAS scenario has primary renewable energy requirement at 1361 TWh/yr so in the same ball park.
  13. Technical assessment of nuclear energy with respect to the ‘do no significant harm’ criteria of Regulation (EU) 2020/852 (‘Taxonomy Regulation’)