The Bank of England has published a staff working paper on product innovation in the UK mortgage market, using green mortgages as the case study. The research finds that Energy Performance Certificates became pricing-relevant in 2018, when lenders started offering lower mortgage pricing for more energy-efficient properties, and that these discounts widened over time, reaching up to 15 basis points in 2022 in offer-level data. The paper develops a framework that treats mortgage products as bundles of attributes and infers innovation from changes in the pricing mix of interest rates and fees. Using transaction-level data matched to Energy Performance Certificates and offer-level data on advertised green products, it finds measurable discounts for loans secured on properties with higher energy efficiency. Mortgages against high-EPC properties are concentrated in new buildings, which the paper says points to looser credit constraints for those borrowers and potentially higher housing investment, with implications for broader economic activity.