Solar energy reached a major milestone in 2025, marking one of the most significant years yet for clean power generation across Great Britain. Strong growth in installed capacity, combined with exceptional weather conditions, helped solar deliver record levels of electricity and further reduce the carbon intensity of the UK power system.
According to industry data, solar accounted for just over six per cent of Great Britain’s electricity generation in 2025 – a substantial increase compared with the previous year. In total, more than 18 terawatt-hours of electricity were produced from solar by mid-December alone, highlighting how rapidly the technology is scaling up across the country.
To put this into context, the energy generated by solar in 2025 was sufficient to meet the annual heating demand of millions of typical homes when paired with low-carbon technologies such as heat pumps, or to power everyday activity on an enormous scale.
Solar’s role in a cleaner grid
This growth forms part of a wider transition in the UK’s electricity mix. As renewables continue to displace fossil-fuel generation, the average carbon intensity of electricity has fallen sharply over the past decade. In 2025, Great Britain recorded its second-lowest carbon intensity on record, a dramatic improvement compared with levels seen in the late 2000s.
Solar power plays a growing role in this shift, particularly during daylight hours when it can significantly reduce reliance on gas-fired generation. Alongside wind and storage, solar is becoming a core pillar of a more resilient, low-carbon energy system.
Capacity growth across all scales
A key driver behind 2025’s record performance was the rapid expansion of installed solar capacity. Total capacity rose by close to a fifth over the year, reaching almost 24 gigawatts by year end.
Growth was seen across the full spectrum of solar deployment:
- Residential rooftops, where installations reached record levels, driven in part by new housing developments increasingly incorporating solar as standard
- Commercial and industrial buildings, where rooftop solar is helping businesses cut energy costs and emissions
- Large-scale solar farms, which continue to deliver substantial volumes of low-cost renewable electricity
One of the standout projects of the year was the commissioning of the Cleve Hill solar farm in Kent. At over 370 megawatts, it is now the largest operational solar installation in the UK and a clear signal of the scale at which solar can be delivered.
Looking ahead, forthcoming policy changes including the Future Homes and Buildings Standards are expected to further accelerate the uptake of on-site solar generation, particularly in new developments.
The impact of a sunny year
Weather conditions also played a role in boosting output. The UK experienced its sunniest year since records began in 2010, with high sunshine hours recorded across all nations. While sunshine levels naturally vary from year to year, 2025 demonstrated how increased capacity ensures that favourable conditions translate directly into meaningful gains in clean electricity generation.
What this means for the energy transition
The record performance of solar in 2025 underlines a broader shift in how energy is generated, supplied and consumed in Great Britain. As costs continue to fall and policy support strengthens, solar is moving from a supplementary technology to a mainstream energy source.
For households, businesses and developers, this presents a growing opportunity to reduce exposure to volatile energy markets, lower carbon emissions and play an active role in the transition to net zero.
At Nero Energy, we see 2025 not as a one-off success, but as a sign of what’s to come as solar continues to scale and integrate with smarter, cleaner energy systems.
