In recent times, the imperative to address the pressing challenges of global energy demands and climate change has intensified. The UK government has made a formal commitment to reduce greenhouse gas emissions to net zero by the year 2050. In 2023, 41.1% of electricity of the country was generated by renewable sources, where 29.4% was generated from wind, followed by biomass (5%) and solar-PV (4.9%). Power generation from renewable energy sources is highly intermittent. For instance, the output of the wind turbines is greater in the nighttime compared to daytime. To achieve the net-zero target while enhancing the share of renewable energy in the electricity mix, it’s necessary to develop energy storage facilities. Pumped hydro energy storage (PHES) is known as ‘world water batteries’ as they store water and generate electricity when an energy balance between the supply and demand of the electricity grid is required, and PHES provides a solution to address the intermittency and reliability challenges that occur from wind and solar. The UK has a significant potential for PHES sites, and most potential sites are in Scotland. The goal of combining solar energy is to optimize reservoir land usage by installing floating solar-PV systems. Financial feasibility was analysed using several parameters, such as the levelized cost of storage, net present value, internal rate of return, and payback period. The study demonstrated the feasibility of four PHES with a power output of 800MW each, which is approximately 22% of the power output of the existing gas power plants in the UK, which accounted for 14GW capacity. LCOS of 5GWh PHES lies between 59.2–59.4$/MWh.