Increasing the energy efficiency rating of all owner-occupied housing to EPC C or higher would cut carbon whilst also slashing energy costs, ensuring 10% of homes per year meet this standard. See the English Housing Survey data on energy inefficient dwellings.
This would cost an average of of £4,385 per home. But cost will fall to owner, with councils facilitating access to grants where available. Haringey (population 271,000) is considering a team of 15 staff, at a cost of £525,000 a year, to achieve improvements to C or better in 86,000 non-council owned homes over next 15 years, or 5,700 a year. Plus a further team of 12 (£420k annual cost) to support households with accessing funding.
(Ashden Action 7 31 Climate Actions for Councils)