- Price Protect tariff shields Portsmouth Water from energy price volatility
- Made possible by Wattstor, a next generation energy company, with expertise in both engineering and commercial energy models
- Set to double Portsmouth Water’s renewable capacity to 6 MW in its biggest clean energy project to date
Portsmouth Water and Wattstor have entered into a long-term agreement to develop a 3MW solar project at the Highwood reservoir. For Portsmouth Water, which serves around 324,000 homes and businesses across South East Hampshire and West Sussex, the venture will double the utility’s renewable capacity to 6 MW. The 25-year agreement uses Wattstor’s Price Protect tariff, which caps electricity costs throughout the full duration of the agreement, to shield Portsmouth Water from market volatility and potential price increases.
In addition to a capped rate, the Price Protect tariff allows Portsmouth Water to benefit if wholesale prices fall. As energy is one of the utility’s biggest expenses, this protection gives the company stability in managing both its operations and costs.
Bob Taylor, CEO at Portsmouth Water, said: “We have committed to being net zero by 2040 and we’ve already nearly halved our gross carbon emissions since 2016. Buying renewable energy generated on our own sites is a crucial part of our plan. Additionally, as energy is one of our biggest costs, protection from price shocks is also very important. Wattstor’s Price Protect tariff has capped our electricity costs at a flat, competitive rate and gave us the certainty to go ahead with this project. That certainty now helps us keep bills fair while continuing to deploy renewables at scale.”
Water companies are under growing scrutiny to keep costs under control while continuing to invest in infrastructure and sustainability. By stabilising one of its biggest overheads, Portsmouth Water is taking a step that supports both affordability for customers and long-term investment in clean energy.
This is the first time a UK water company has taken this approach but the model is scalable. By combining a capped-price tariff with solar-plus-storage, Wattstor has shown how water companies can build resilience while protecting customers from higher costs and unlock renewable schemes that would otherwise not go ahead or would go ahead with a much smaller level of solar deployment.
Kevin Ball, Chief Commercial Officer at Wattstor, said: “This project depends on tackling the engineering and the commercial model side by side. With a DC-coupled solar-plus-storage system, deployed through a Price Protect tariff, Portsmouth Water can now make full use of the reservoir roof area, which will lead to over 85% of the annual electricity demand being renewably generated onsite.”
Unlike standard AC-coupled systems, Wattstor’s DC coupling allows solar projects to generate beyond the allowable grid generation capacity caps by directing solar energy straight into onsite batteries before converting to AC power. This design ensures every kilowatt is first used on site rather than curtailed or exported at uneconomic periods. It unlocks viable roof top areas for PV, that would otherwise have been wasted and makes a far larger carbon reduction for the pumping station operations than a standard scheme.
The Highwood site also requires careful environmental management. The reservoir is fully roofed to prevent algae growth and sits alongside a country park and wildlife habitats. Wattstor has designed the project to minimise disruption, with all cabling set to be installed underground using directional drilling rather than open trenching. This will preserve public paths and green spaces, protecting biodiversity and allowing the project to be delivered without disturbing the landscape. The result is a renewable scheme that will be delivered with care to minimise impact on the reservoir’s surroundings.
