renewable energy source

Hi,
As power generated by renewable sources goes into the national grid, how do you know that the power Bulb purchases comes from those resources and not a nuclear power station?

http://community.bulb.co.uk/discussion/73/where-does-bulb-get-it-s-energy-from

Thanks, @phproxy , @richard3495 Also see this page on our website as well https://bulb.co.uk/energy/whereitsfrom