Repowering offers an opportunity not just to build bigger wind farms, but to build more productive ones. The next phase of the energy transition may therefore be judged less by how many megawatts we install and more by how many megawatt-hours we deliver, writes Philip Nurse, Head of Renewables at Gneiss Energy.
For two decades, the renewable energy industry has been obsessed with megawatts.
We measure success in MWs consented, MWs connected, GW targets, £/MW acquisition values and MW connection offers. Planning applications are assessed in MWs. Grid queues are managed in MWs. Developers promote portfolios in bragawatts. Investors value projects in £/MW.
In many ways, this makes perfect sense. The electricity network is designed around capacity. Transmission lines, substations and connection agreements are ultimately constrained by how many megawatts they can transport at any given moment.
Consumers do not use megawatts, and projects don’t sell megawatts. They use and sell megawatt-hours.
And as Scotland’s first generation of onshore wind farms approaches end-of-life, repowering may finally force the industry to ask whether we have become too focused on capacity and not focused enough on production.
The repowering opportunity might not be what most people think
Much of the current debate centres on bigger turbines, taller towers and higher installed capacities. The assumption is simple: bigger is better. However, when we run the numbers, repowering poses a different question and may support a very different conclusion. What if the greatest opportunity is not to increase installed capacity at all but rather to generate more energy from the capacity we already have?
Consider a simple thought experiment: If Scotland’s existing onshore wind fleet were able to increase its average capacity factor from 28 percent to 40 percent, annual generation would increase by approximately 11.5TWh. That is broadly equivalent to adding around 4.7GW of additional onshore wind operating at a 28 percent capacity factor, with no increase in installed capacity.
This debate is particularly pertinent because repowering remains largely absent from the National Energy System Operator’s (NESO) long-term planning assumptions. While NESO’s Future Energy Scenarios examine a range of pathways to net zero, they focus primarily on the deployment of new generation capacity and do not explicitly recognise the contribution that widespread repowering could make to future electricity production.
Why this matters
That omission matters. If existing wind farms can generate substantially more energy through improved capacity factors, modern turbine technology and more productive use of existing grid connections, then future electricity supply may be understated in current scenarios.
In effect, repowering has the potential to deliver the energy equivalent of several gigawatts of new capacity without requiring the same scale of new network infrastructure, planning consents or grid connections.
Scotland already generates more electricity than it consumes. In 2024, Scotland generated around 38.4TWh of renewable electricity and exported almost 20TWh of net electricity to the rest of the UK. Renewable generation was already significantly greater than domestic demand.
This means the energy transition increasingly becomes less about simply connecting more capacity and more about maximising the value of the infrastructure we already have. Of course, capacity remains important and relevant but maybe not quite as relevant as it once was.
The hidden value of capacity factor
A higher capacity factor does more than increase generation. It increases the productivity of scarce infrastructure. A 100MW grid connection is still a 100MW grid connection regardless of the capacity factor. A wind farm operating at a 40 percent capacity factor delivers substantially more energy through that infrastructure than one operating at 28 percent.
What if the connection agreement does not change, the substation does not change, the transmission corridor does not change but the quantity of clean electricity delivered through that infrastructure increases dramatically?
Beyond wind
This issue extends far beyond repowering onshore wind.
Solar, wind, battery storage and hydro are frequently discussed and valued through the lens of MW. From a system perspective, MW is only part of the story. What really matters is how much energy is generated, when it is generated, how frequently it is generated, how effectively scarce grid capacity is utilised, and how much value is delivered to consumers. These are all fundamentally MWh questions.
A different conversation
Repowering may ultimately do something unexpected. It may shift the conversation away from expansion and towards productivity. If Scotland can unlock the energy equivalent of several gigawatts of new wind capacity simply by improving the performance of the fleet it already has, then perhaps the most important question is no longer: How many megawatts can we build but how many megawatt hours can we deliver?
For decades, the renewables sector has measured progress in megawatts because megawatts were the scarce resource. Yet as mature wind fleets are repowered and grid capacity becomes increasingly constrained, the scarce resource may no longer be turbine capacity but the ability to maximise energy production from the infrastructure already in place.
Repowering offers an opportunity not just to build bigger wind farms, but to build more productive ones. The next phase of the energy transition may therefore be judged less by how many megawatts we install and more by how many megawatt-hours we deliver.
