The government has set targets for UK solar PV electricity generation capacity of up to 45–47 GWp (gigawatt peak) by 2030 and 75 GWp by 2035. These targets have been adjusted upwards in the past year by seemingly adding in current embedded solar capacity (19 GWp as of end 2024) or, in the case of the 2035 target, the growth in embedded capacity over the last decade.

Taken together with the recent combining of distribution and transmission level connection targets, there appears to be a strong bias in government towards transmission-scale projects. The Nationally Significant Infrastructure Project (NSIP) process is strongly geared to granting development consent orders even against the advice of the Planning Inspectorate. No applications have yet been refused.

Detailed modelling shows that 45 GWp of solar PV can only contribute around 14.5% of Great Britain’s annual electricity demand (2024 figures), rising to around 16% if four-hour battery energy storage (BESS) is used to avoid summer curtailment. Demand is set to at least double in the next 15–20 years, and a capacity of 75 GWp would only satisfy just over 13%, even coupled with BESS.

In addition, the proportion of PV energy is very small in winter, during high demand, which greatly exceeds summertime demand. This mismatch of generation and demand will mean expensive firm generation will be required in winter and curtailment will occur in summer.

Also, if solar PV were to provide for all the summer demand, this would lead to curtailment of all other generation assets on the system, including offshore wind. Curtailment payments would be extremely costly, outweighing any cost advantage that solar might have, keeping prices to consumers high while the generators profit. Negative pricing signals may even find the system scrabbling to find new demand to keep the industry profitable.

Is solar worth the land it requires?
At current installed and proposed PV densities, the land required is around 2,000 ha/GWp (about two large airports in size). The modelling shows 1 GWp of PV can generate around 870 GWh per year. At 2024 electricity demand levels, this means that 2,000 ha of land is required to generate around 0.35% of Great Britain’s electricity requirements (this percentage will fall as electricity demand rises). The solar facility therefore generates around 870/2,000 = 0.435 GWh/ha. A 1 GW combined cycle gas turbine (CCGT) power plant (with 60% availability) on 10 ha of land can produce 525 GWh/ha, or around 1,200 more energy per ha than solar.

Most targeted land to date is high-grade agricultural land. Despite government claims that 0.1% of farmland will be required, some counties are seeing over 5% of high-grade farmland being proposed to go under solar panels. Use of arable farming land, with little or no livestock management, will see the removal of productive land for at least 40 years, and most likely forever. As electricity demand increases, the moving target of generation capacity will require an accelerating demand for land.

With over 130 GWp of large scale solar in the planning pipeline, this would sacrifice a land area equal to the size of Derbyshire. In the absence of a Land Use Framework and Strategic Spatial Energy Plan (SSEP), there is no proper oversight on the deployment of these facilities.

Co-location of BESS with large-scale solar is becoming the norm, and while direct solar sales are subject to a price cap under contracts for difference (CfD), this is not the case for co-located BESS. BESS is needed to avoid summer curtailment, but it is also used in winter to store electricity generated during periods of low system price (midday in winter for example) to sell at peak demand times when the system marginal price is high. This use of arbitrage bypasses the CfD cap and provides additional revenue to the solar operator, again keeping bills high.

Many BESS systems are being proposed for sensitive sites, including source protection zones where ground water finds its way into aquifers. The risks of contamination from BESS fires, which are not uncommon, can have extreme consequences. Concentration of BESS, for which there are no safety guidelines or regulations, into facilities of 1–2 GWh of storage present a hazard that requires levels of care in siting and management that are currently absent or untested.

When solar PV provides all the summer demand this would lead to curtailment of all other generation assets on the system, including offshore wind. Curtailment payments would be extremely costly, outweighing any cost advantage that solar might have.

Is small-scale solar the answer?
Embedded and distributed solar systems have a different dynamic altogether. These include rooftop systems, carpark canopies, retail parks, warehouses and small-scale ground base systems, with an estimated total combined potential capacity of almost 120 GWp. These can be locally owned, with benefits flowing directly to end users; battery systems are used to avoid peak prices and help with overall load management.

Embedded assets serve to remove load from the transmission system, which can avoid transmission level upgrade costs. This is a competing interest with transmission scale projects as it reduces their market. In Australia, for example, this is dealt with by the grid being able to remotely disable rooftop generation.

The government’s main argument for large scale systems cites build cost advantages. However, this does not account for the hidden costs of land sacrifice, biodiversity loss and the added operational costs to the UK energy system. The UK will remain the most expensive electricity market in Europe, while delivering inadequate carbon abatement.

A policy of energy efficiency investment alongside embedded solar PV is a far more rational one that would ultimately deliver better outcomes for consumers and the environment.

The views and opinions expressed in this article are strictly those of the author only and are not necessarily given or endorsed by or on behalf of the Energy Institute.
 

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• As the world electrifies, meeting rising electricity demand and connecting new wind and solar generation will require large-scale investment in transmission and distribution infrastructure. Building new infrastructure is essential, but it is not the only solution, as innovative grid technologies (IGTs) – both hardware and software-based – offer a complementary route. Discover more about the case for innovative grid technologies.