• Currently, hydrogen is expected to play a limited role in the decarbonisation of residential and commercial low-grade heating. However, in regions where policies support its adoption, hydrogen may see greater use, including the potential for blending up to 20% into existing gas networks.

A wide range of sustainable methods for providing low-grade heating in residential and commercial buildings is already in use worldwide, to varying degrees. These methods include  (electric) heat pumps or low-carbon district heating.

The use of low-carbon gas such as hydrogen, synthetic natural gas, and biogas for low-grade heating in buildings remains minimal at present; however, numerous research projects and trials are exploring their potential worldwide, including initiatives like HyDeploy and H100 Fife in the UK.

Using hydrogen safely at homes

Replacing fossil fuel in heating is a complex and costly process that faces several technical and economic barriers, with solutions likely varying by region. Key obstacles include the high upfront costs of renewable heating technologies, the need to retrofit the existing fuel and heat distribution systems, limited consumer awareness and trust in alternative low-carbon options, inconsistent policy support and incentives, the limited availability and accessibility of renewable energy sources, and the potential environmental and social impacts of some of the alternatives.

If natural gas is replaced with 100% hydrogen, heating and cooking appliances will need to be adapted or replaced due to hydrogen's different properties, such as its higher combustion temperature and increased flammability. To address these challenges and ensure safety in homes, several precautionary measures are recommended, including enhanced ventilation (which may involve permanent vents), the installation of hydrogen detectors, and the incorporation of other safety measures. For more details, refer to the What are the main challenges and potential solutions? section.

Companies such as Worcester Bosch, Giacomini, and BDR Thermea (BAXI) are already developing hydrogen-ready appliances for use in homes. These appliances would work normally with natural gas but could also be used with hydrogen if the gas supply switched over. In the UK, research projects like Hy4Heat and HyHouse have evaluated the risks associated with using hydrogen in residential applications, contributing valuable insights into safety requirements and mitigation strategies.

Implementing these safety measures and utilizing hydrogen-ready appliances are crucial steps toward safely integrating hydrogen into residential energy systems.

Boilers: Natural gas boilers are equipped with a flame failure device, which uses sensors to stop the gas flow if the flame extinguishes. The sensors used in natural gas boilers are incompatible with hydrogen, but engineers are working on new safety technologies that use infra-red or ultra-violet light. To ensure the safety of hydrogen boilers, these devices will need to be fast-acting and reliable.

Fires: Hydrogen burns with a pale blue flame which is almost invisible to the naked eye. To enhance both visibility and safety, a chemical colourant could be added to the flame, making it more noticeable and visually appealing. Ongoing research aims to find a suitable colourant that is cost-effective, non-toxic, and compatible with hydrogen. Another alternative would be to design a heating element that glows when in use.

Cookers and ovens: Hydrogen cookers would require re-designed burners to manage the higher temperatures at which hydrogen burns and to limit the release of harmful NOx gases. Elevated levels of nitrogen dioxide (NO₂), a common NOx gas, can damage the human respiratory tract and increase vulnerability to respiratory infections and asthma. Long-term exposure to high levels can even lead to chronic lung disease. To mitigate this, design modifications such as reducing the size of burner holes, using new materials, or other methods of limiting oxygen concentration at the point of ignition may be necessary. Importantly, using hydrogen is not expected to impact cooking performance or require new kitchen utensils.

Hydrogen blending

An interim step for using hydrogen in residential heating could involve blending up to 20% into the existing natural gas supply. This approach would require relatively little investment in existing pipelines and cause less disruption to household appliances. However, it would only result in a relatively modest CO₂ saving of around 6%, and concerns about hydrogen's availability and sustainability are likely to persist. Additionally, safety and flammability issues must be addressed - though they are less critical at this lower concentration compared to the challenges posed by 100% hydrogen.