Residential buildings account for approximately 17% of global carbon emissions, making housing decarbonization central to climate goals worldwide. In response, green mortgages—loans offering preferential terms for energy-efficient properties—have proliferated across markets. In the US, Fannie Mae and Freddie Mac now offer green financing programs, while European lenders have rapidly expanded similar products under the EU Taxonomy framework. Over 140 banks representing $74 trillion in assets have committed to Net-Zero targets aiming to provide financial solutions such as green mortgages to their clients as they seek to transition to a low-carbon economy. But do these products genuinely incentivize the green transition, or do they primarily serve as marketing instruments?
We examine this question using nearly four million daily mortgage product offerings from UK lenders between May 2022 and September 2023, a market where green mortgages now comprise 10-15% of offerings. The UK’s competitive, transparent mortgage market and standardized energy efficiency ratings provide an ideal setting to identify the true drivers behind green mortgage pricing, with implications for green finance programs globally.
What Green Mortgages Offer
Green mortgages in the UK are designed for properties with Energy Performance Certificate (EPC) ratings of A, B, or C, the top three tiers on the energy efficiency scale. Lenders offer two distinct types of benefits on these products: preferential interest rates and upfront cashback payments.
Our analysis reveals substantial heterogeneity across these benefit types. Green mortgages with preferential interest rates offer an average discount of approximately 9 basis points relative to equivalent non-green products when comparing green and non-green products offered by the same lender. For a typical £200,000 mortgage, this translates to annual savings of approximately £180, whereas upfront cashback incentives amount to only around £49. These estimates are substantially larger when comparing across lenders (see figure below). Overall, the economic magnitude of benefits associated with upfront cashback incentives is substantially smaller than that associated with preferential interest rates.
Why Do Lenders Offer Green Mortgages?
The central question for policymakers is whether green mortgage benefits reflect genuine economic fundamentals that support the green transition, or whether they reflect bank’s strategic considerations. We investigate two hypotheses.
The credit risk hypothesis suggests that energy-efficient properties carry lower default risk, either because reduced utility costs improve borrowers’ cash flows, or because such properties are more likely to preserve their collateral value and be more resilient to a “brown discount.” Our evidence does not support this explanation. We find no systematic relationship between green mortgage benefits and measures of credit risk.
Instead, our findings strongly support the customer acquisition hypothesis. Green mortgages appear to function primarily as a product differentiation strategy. We find that green mortgages are significantly more likely to be offered to homebuyers than to borrowers refinancing existing mortgages, consistent with lenders using them to compete for new borrowers at the point of purchase, and this pattern is especially pronounced for cashback-based green products.
Cashback plays a central role in this strategy. Although cashback offers provide smaller annual-equivalent financial benefits than preferential interest rates, they are highly salient to borrowers because they are received upfront. We find that cashback-based green mortgages are more likely to be available for new-build properties and shared ownership schemes, settings in which borrowers are more likely to face liquidity constraints and therefore place greater value on immediate cash benefits. Consistent with this interpretation, we also find that the cashback benefits are concentrated in the owner-occupied segment, whereas preferential-rate benefits are more prevalent in the investor segment, where borrowers are less likely to face liquidity constraints and respond more strongly to interest-rate savings over time.
Implications for Climate Policy
These findings carry important implications for green finance initiatives worldwide.
First, green mortgages in their current form may not substantially alter incentives for investments in improving the energy efficiency of the housing stock. The financial benefits are modest: a 9-basis point discount or upfront cashback offers may reward borrowers who already choose energy-efficient properties, but they are unlikely on their own to change purchase decisions or finance costly retrofits.
Second, the prevalence of green mortgages in lenders’ Net-Zero commitments warrants scrutiny. If these products primarily redistribute existing demand rather than stimulate new energy-efficient construction or renovation, their contribution to climate targets may be limited: a consideration equally relevant for US programs like Fannie Mae’s HomeReady Green and European initiatives under the EU Taxonomy.
Third, standardization and transparency around green mortgage definitions could benefit both consumers and energy transition objectives. Currently, the “green” label encompasses substantial variation in eligibility criteria and benefit structures across lenders and jurisdictions.
Our findings suggest that borrowers purchasing energy-efficient homes do receive tangible financial benefits from obtaining green mortgages. However, policymakers worldwide seeking to accelerate decarbonization in the real estate sector should recognize that market-based green finance products may serve commercial objectives that only partially align with broader climate-transition goals. More direct policy interventions, such as subsidies for retrofitting or stricter building standards, may therefore be necessary complements.