[MargaretR]

I have looked at the site.
I wanted to see a tariff so that I can compare that supplier with mine, but no tariff is shown anywhere.

The section for our completion asking about usage, asks for current supply costs in £s.
In order to make an accurate comparison you need to use KWH used, not £s spent, as a base and compare tariffs.

I am skeptical whether this company will do what it says it will.
The cost of supply to them will depend on how big their customer base is.
More customers give them a better deal from gas and electricity producers, and a better chance of being cheaper than the mainstream.