"Over the last ten years environmental and social costs have risen from £10 to over £100. Compared to 2012, environmental and social costs have risen by around £10 to £115 of an average annual dual fuel household bill. If current trends continue, we anticipate environmental and social costs to increase further over the next 12 months."
"Environmental costs" refers to the subsidy paid to wind farm owners when the wind isn't blowing hard enough, or is blowing too hard, to produce electricity - which is when the "social costs", or subsidised backup diesel generators, kick in. Both of these subsidies are added to our electricity bills.
As more coal-fired power stations are shut down because, like diesel generators, they produce carbon dioxide, then more wind farms and generators will be required, and the amount of subsidy added to our electricity bills will therefore go up. Hence Ofgem's anticipated increase in "environmental and social costs".
On the other hand, if we opened up more coal-fired power stations (like Germany), freely exploited shale gas (like the USA) and burned down our windmills, then we could have cheap electricity - and gas - instead. As the Ofgem link page shows, the wholesale price of natural gas has risen by 240% over the past 10 years.