Mott MacDonald has led, since 2024, a multidisciplinary alliance of built environment, energy, retrofit, and finance specialists where we collaborate with the Greater London Authority (GLA) and the Energy Savings Trust to help London’s public sector organisations overcome the hardest part of the net zero challenge: retrofitting thousands of pre-existing, aging, and unique buildings across the 32 London boroughs as part of the Zero Carbon Accelerator (ZCA) Programme.

The ZCA is the Mayor of London’s flagship technical assistance programme to help London’s public sector decarbonise in line with London’s ambitious climate targets. London is embarking on an unprecedented effort to decarbonise one of the world’s largest, oldest and most complex public sector estates by 2030 which requires an estimated infrastructure investment of £75 billion over four years.

Delivering important decarbonisation outcomes is a feat that no single team could achieve alone. Thanks to our alliance of specialists, alongside the Energy Saving Trust’s marketing, engagement and communication team, we can successfully and simultaneously deliver multiple heat decarbonisation, renewable energy analysis, energy systems modelling, commercial planning, programme governance, and stakeholder engagement for London’s building owners, local authorities, housing providers, and other asset holders in seek of support but may be constrained by technical complexity, skills gaps, fragmented portfolios, or limited access to finance.

The GLA Multi Year Framework reflects the scale of decarbonisation ambition and opportunity in the city which the ZCA is best positioned to achieve. 2025 saw a particularly successful, delivery focused year for the ZCA thanks to our end-to-end support to the GLA and its boroughs. 150,000 MWh per year of energy savings and 66,500 tCO₂e annual emissions reductions has been achieved across 20 individual projects delivered in 2025 thanks to collaboration occurring across all levels, from the GLA executive to local authority borough level.