So I had a look and found this https://www.mygreenstarenergy.com/Our-Energy-Tariffs/Unlimited-Tariff
They offer a fixed monthly rate which basically averages out the seasonally varying energy consumption but of course if your consumption is significantly higher than what could expected from your profile they would require you to change the monthly payment. I'm pretty sure they have a clause to that effect in their contracts.
Unlimited free energy is every miner's dream, but in reality, energy that you consume has to be paid for somehow by somebody. Don't expect others to pay for your energy consumption for very long...
You can harness natural energy sources such as wind, water, sunlight but then you still have to invest into the equipment and pay for maintenance at regular intervals, so even that kind of energy isn't free.
Onkel Paul