In the IEA Net Zero Emissions by 2050 Scenario, the use of modern renewable heat in buildings expands twice as fast as in our outlook, and almost three times as fast in industry.

The largest discrepancies are seen in modern bioenergy use, with additional growth of 5.1 EJ during 2021-2026 under the Net Zero Emissions Scenario compared to our outlook, almost evenly split between the industrial and buildings sectors. In industry, this gap comes primarily from greater use of municipal solid waste in the cement subsector, and greater reliance on on-site residues for pulp

and paper industries in the Net Zero Emissions Scenario. In buildings, the wider rollout of improved biomass cookstoves enables further substitution of traditional uses of biomass.

Assuming both more rapid penetration of renewables in power generation and greater electrification of heat through heat pumps and direct electric processes (e.g. induction or electric arc furnaces for secondary steelmaking), the Net Zero Emissions Scenario sees thermal uses of renewable electricity in industry expanding twice as fast as in our outlook. In buildings, behavioural changes and envelope retrofits completely offset additional electricity consumption associated with the massive deployment of heat pumps described in the Net Zero Emissions Scenario. The number of heat pumps installed in buildings globally is 50% larger than in our outlook by 2026, expanding to 600 million units by 2030, driven by the introduction of bans on fossil fuel boilers. By 2030 heat pumps meet 20% of energy demand for heat in buildings, up from 5% in 2019 (IEA, 2021c; REN21, 2021).

Direct solar thermal consumption grows more than 2.5 times as fast during 2021-2026 in the Net Zero Emissions Scenario than anticipated in our outlook, a difference of 1.1 EJ. The addition is both from the installation of solar thermal water heaters in buildings and the take-off of solar heat for industrial processes. Accordingly, the number of dwellings using solar thermal systems rises from 250 million in 2020 to 400 million by 2030, and up to 1.2 billion in 2050 (IEA, 2021c).

Finally, the Net Zero Emissions Scenario sees the exploitation of the decarbonisation potential of existing district heating networks far beyond our current projections, with more than a doubling of the share of renewables in global district supplies by 2026. Under these assumptions, renewable district heat consumption needs to grow six times faster than in our outlook, with contributions not only from bioenergy – the largest renewable source for district heat – but also from solar thermal and large-scale heat pumps.

In the longer term the Net Zero Emissions Scenario also sees a growing – yet limited – role for renewable gases such as biomethane and renewables-based hydrogen for heating, in specific contexts, both in buildings and industry. These renewables-based energy carriers can be introduced by progressive blending, taking advantage of existing gas infrastructure, and provided end-user appliances are compatible with blending levels. They can also be used in hybrid systems that combine electric heat pumps with gas boilers.

Beyond highlighting opportunities to expand the supply of renewable heat, the Net Zero Emissions Scenario emphasises the critical importance of simultaneously containing heat demand through behavioural change, material efficiency and energy efficiency. For instance, the scenario’s total global heat demand is 13% lower (9% lower in industry, 18% lower in buildings) than in our current projections for the year 2026. Targeting the substitution of traditional uses of biomass with more efficient cooking and heating technologies is also a critical element of the Net Zero Emissions Scenario to achieve progress towards more sustainable use of renewable sources. An important multidimensional policy gap remains to be addressed to bring heat-related CO₂ emissions in line with Paris Agreement ambitions.