It is policy to encourage lower usage, like it is policy to keep prices up (both production and the grid are a shamble, not to mention climate commitments on top). Maybe the policy isn't publicly stated but actions speak louder than words. Of course this isn't popular so, at the same time, the governments takes measures to appear to try to keep prices lower. It is a political balancing act and subsidies are not incompatible with a policy of encouraging lower usage.

It's the same as they are doing on immigration: They say they want to lower it but the actual policy is to keep it high. People have understood that now, which explains in big part the Conservative wipe out. Labour is now on the same path.