In some places which aim to phase out fossil fuels in favor of low carbon power, such as the United Kingdom, seasonal energy storage is difficult to provide, so having renewables supply over 60% of electricity might be expensive. whether interconnectors or new nuclear would be more expensive than taking renewables over 60% is still being researched and debated. Britain's older gas-cooled nuclear reactors are not flexible to balance demand, wind and solar, but the island's newer water-cooled reactors should have similar flexibility to fossil fueled power plants. According to the operator from 2025 the British electricity grid may spend periods zero-carbon, with only renewables and nuclear. However actually supplying the electricity grid only from nuclear and renewables may be done together with interconnected countries, such as France in the case of Britain.