Hydrogen’s Impact on End-Use Appliances

How the shift to hydrogen – natural gas blends will affect home appliances

Part 1

September 2023

As key players in the utility industry begin piloting hydrogen projects to meet their carbon reduction goals, one of the main questions consumers are asking is how the shift to hydrogen – natural gas blends will affect their home appliances. Today, consumers use natural gas to prepare their meals and heat their homes. The main appliances in a residential home utilizing natural gas are:

  1. Cooking appliances such as ovens, grills, stoves
  2. Dryers
  3. Air conditioners
  4. Refrigerators and freezers
  5. Water Heaters
  6. Radiators

Citation: Bolt, 2023

Will these appliances be able to sustain the hydrogen transition, or will a blend of natural gas and hydrogen require consumers to replace their appliances? This question along with the pros and cons of each are being evaluated extensively.

Performance of Appliances

Recent studies have proven current natural gas appliances are sustainable for a hydrogen blend of up to 20% (Font, Kernan, Widder, 2023). Specifically, studies conducted by the Canada Standards Association (CSA) proved appliances to still be high performing with 5% and 15% hydrogen blends. Once the hydrogen blend surpasses 20%, the performance of an appliance begins to deteriorate and cause safety concerns, which would require shifting to hydrogen appliances.

There are multiple parameters for determining the performance of a residential appliance such as ignition, burner operating characteristics (BOC), temperature rise, combustion, flue loss, and condensation (Suchovsky, Ericksen, Williams, Nikolic, 2021). However, these parameters proved to have the most variation when testing with hydrogen blends, causing concern (Font, Kernan, Widder, 2023) :

  1. Combustion

    Hydrogen has a higher combustion rate than natural gas by 4.25 m/s, meaning it “requires less oxygen than burning the equivalent amount of natural gas” (Guarco, Langstine, Turner). The combustion of hydrogen releases water and no carbon dioxide; moreover, it also will require less oxygen than a standard combustion reaction resulting in surrounding air being heated to a greater degree than natural gas. Due to the higher heated air content, the performance of the appliance suffered since the temperature of the flame is affected by the higher air temperature and combustion reaction. Studies have shown “the effect on tested appliance efficiency is minimal, varying only 1 to 1.5% for 30% hydrogen blend in natural gas”, leading to concerns with 100% hydrogen or higher blends (Font, Kernan, Widder, 2023).

  2. Condensation

    Like the increased rate of combustion, hydrogen also produces more condensation in comparison to natural gas. This difference becomes a concern especially in reference to dryers. Condensation in dryers can cause a performance issue due to additional moisture build-up, creating the need for equipment upgrades. In appliances other than dryers, condensation is a point of concern due to necessary improvements needed to ventilate the additional moisture, if the ventilation system is not already established. The NEEA, Hydrogen-Ready Appliances Assessment Report, determined that a 20% hydrogen blend will cause an 8% increase in condensation.

  3. Flame
    Fig 1 – Different hydrogen blend percentages and the resulting flame (Font, Kernan, Widder, 2023)

    The color of a hydrogen flame becomes relevant with appliances such as hearths and stove tops. Many consumers use the flame as a detection for safety and strength. A flame can notify the consumer whether the appliance is continually heating and ultimately, if the appliance is still on. With a hydrogen flame, as the hydrogen blend increases, the flame becomes more difficult to see, in addition to being odorless, resulting in safety concerns (Kiwa, 2016). Figure 1 shows the variation of flame colors for different variations of hydrogen blends. Likewise, many appliances use ionization sensors to detect flames or thermoelectric flame failure devices. Due to the inability of these sensors to detect hydrocarbon combustion, many safety features of appliances will begin to fail at higher hydrogen blends and may cause gas build up, leading to safety concerns (Font, Kernan, Widder, 2023).


Hydrogen is slowly beginning to be blended with natural gas and entering residential homes. With this transition comes concern of how the blend will affect consumer appliances and whether it will be a cause for homes to upgrade to new equipment. Current studies show that today’s equipment feasibly sustains a hydrogen blend of up to 20%. However, blends of higher than 20%, may compromise performance and safety of existing gas appliances, requiring an upgrade to 100% hydrogen appliances.


  1. https://energytheory.com/what-appliances-use-gas-in-the-house/
  2. https://neea.org/resources/hydrogen-ready-appliances-assessment-report
  3. https://cea.org.uk/practical-considerations-for-firing-hydrogen-versus-natural-gas/
  4. https://www.kiwa.com/48cef0/globalassets/uk/reports/decc-hydrogen-appliances-report.pdf

Part 2


September 2023

This second part of the series will focus on the future, with a lot of development originating in the United Kingdom, addressing the appliance options moving forward and how the market today is changing. The United Kingdom, Japan, Germany, and Australia are among some countries proving to be the trailblazers for 100% hydrogen ready appliances with companies such as Rinnai, Viessmann, Enertek International, and Worchester Bosch already producing 100% hydrogen compatible products.

Hydrogen Appliance Options

For hydrogen blends above 20%, there are three main options for appliances: new 100% hydrogen appliances, modification of existing natural gas appliances to also function on hydrogen, and new appliances that can function on both hydrogen and natural gas (FNC, 2018). The CADEO group states “product adjustments are necessary for 100% hydrogen” usage in appliances (CADEO).

  1. Adaption and New 100% Hydrogen Appliances

    For an appliance to be adapted and function on hydrogen blends of higher than 20%, the two main modifications that need to occur are to the burner design and ionization sensor. The improved burner design will consider the Nitrogen Oxide production, flame temperature, and combustion, as well as mitigate the risk of flashback(CADEO). The CADEO Group explains a flashback being “the quality in which a fame travels so quickly that it burns backward into the fuel line” and a primary safety concern. For higher hydrogen blends, the burner design needs to be non-aerated to function safely as it “enables more complete combustion of the hydrogen at higher temperature, hereby increasing the thermal efficiency” (CADEO). An ionization sensor is an important part of appliances as it is used as a smoke detector. According to the National Fire Protection Association, it works by “disrupt(ing) the flow of ions, thus reducing the flow of current and activating the alarm” when it recognizes smoke in the environment. However, ionization sensors cannot be utilized with hydrogen above 30% blends because “hydrogen combustion does not produce hydrogen ions” (FNC). Therefore, the ionization sensor method must be updated in hydrogen ready appliances with technology such as ultraviolet or infrared sensors.

    Appliances that can perform on 100% hydrogen are already on the market with industry leaders like Worcester Bosch producing “Hydrogen Ready Zero-Carbon Boiler” as show in figure 1. Worcester Bosch explains that the new product “is a gas-fired heating boiler which is capable of burning either natural gas or pure (100%) hydrogen” (Worchester-Bosch). Worchester Bosch has shared that to make this boiler hydrogen compatible, engineers modified the flame detector to operate safely in hydrogen.

    Looking forward on how to transition to hydrogen appliances, the Heating & Hotwater Industry Council developed a plan to begin “installing hydrogen-ready appliances that work on natural gas when installed and following a simple conversion, are modified to use 100% hydrogen at a future date” (HHIC). This plan aligns with the Worchester Bosch product, as the company stated that “converting a hydrogen-ready boiler from natural gas to hydrogen will take around an hour and involve changing a couple of components as the burner” (Worchester-Bosch). Worchester Bosch plans to educate Gas-Safe engineers on how to complete this conversion.

  2. Functionality of both Hydrogen and Natural Gas on Appliances

    The Frazer-Nash Consultancy group led the hydrogen appliance analysis project in the United Kingdom and ultimately decided that while a dual fuel appliance was possible through innovation, it was not an attractive option for consumers or the industry (FNC, 2018). This decision came due to the technical considerations on how to operate two different fuel types on one appliance. Since hydrogen and natural gas will need two different burner systems and components, the final appliance design would be larger and more expensive than traditional natural gas appliances.

Hydrogen Appliances Today

Rinnai, a gas appliance company, has developed “the first ever 100% hydrogen water heater” which “produces 0% carbon emissions” (Rinnai). The company, like many others, is taking steps to meet net-zero emissions goals and is adapting their appliances to renewable energy sources.

To aid in the transition from natural gas to hydrogen, the UK has taken measures to label appliances according to compatibility. The first label is used for appliances compatible with a hydrogen blend of up to 20%, the second label is used to signify the capability of running on 20% hydrogen blends but being easily convertible to utilize 100% hydrogen, and the third label signifies an appliance can perform with 100% hydrogen.


The biggest concern for many consumers when discussing the conversion from natural gas to hydrogen is the cost of appliances that are needed for a residential home. The leaders of hydrogen ready products in the UK have made a “pact” to price hydrogen boilers at the same cost as natural gas boilers. Merrett writes “Ideal, Baxi, Worcester Bosch and Vaillant have agreed that a new generation of boilers that can be converted to run on hydrogen will cost no more than equivalent systems running on natural gas”. This is one of the steps that is being taken to help consumers afford an appliance conversion and ultimately, achieve the UK’s goal of net-zero by 2050.

WarmZilla, a modern boiler, EV charger, and smart home installation company based in Wales, developed the price comparison in figure 3. Figure 3 shows the average costs with installation of a combination, system, and conventional hydrogen boilers (WarmZilla, 2022). All three of these boilers can currently run on natural gas; however, the combination boiler can later be transitioned to running on hydrogen asdescribed earlier in this article with a one-hour conversion by Worcester Bosch. According to WarmZilla, here are the descriptions of each type of boiler:

  • Combination (combi) Boiler: “water heater and a central heating unit, all in one neat little package”
  • System Boiler: “ideal for homes with high hot water demand”
  • Conventional Boiler: “oldest boiler type on the market” and “known as heat only”

WarmZilla shows that the combination boiler, which has the capability of converting to hydrogen fuel, is cost competitive to conventional boilers.


Moving forward, home appliances need to eventually be converted to function with higher than 20% hydrogen blends. Traditional gas appliance companies have begun to sell products that are compatible with 100% hydrogen or can be easily updated to be compatible. The development of these new products includes adaptation of the ionization sensor and burner design to function properly with hydrogen. The United Kingdom is beginning to put together a transition plan to hydrogen compatible appliances that considers the cost concerns of consumers. To address cost concerns, four large manufacturers plan to keep new appliance prices competitive with traditional natural gas appliances. This plan in the United Kingdom can serve as a model for similar changes in other parts of the world as countries work to lower their carbon emissions.


  1. https://neea.org/resources/hydrogen-ready-appliances-assessment-report
  2. https://www.factoryheaters.co.uk/post/new-hydrogen-appliance-labelling
  3. https://rinnai.co.nz/the-first-ever-100-hydrogen-water-heater
  4. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/699685/Hydrogen_Appliances-For_Publication-14-02-2018-PDF.pdf
  5. https://www.worcester-bosch.co.uk/hydrogen
  6. https://www.hhic.org.uk/uploads/62CFE776309E6.pdf
  7. https://www.nfpa.org/Public-Education/Staying-safe/Safety-equipment/Smoke-alarms/Ionization-vs-photoelectric
  8. https://static1.squarespace.com/static/5b8eae345cfd799896a803f4/t/616d78c680bd847c4efade9a/1634564294494/Bosch+HyLife+.pdf
  9. https://www.biee.org/wp-content/uploads/2021/05/Dodds-Options-and-costs-of-using-hydrogen-for-heating.pdf
  10. https://www.energynetworks.org/industry-hub/resource-library/gas-goes-green-hydrogen-cost-to-customer-report.pdf
  11. https://www.warmzilla.co.uk/boiler/boiler-comparison
  12. https://www.viessmann.family/en/what-we-offer/climate-solutions/hydrogen/100-percent-hydrogen-operation-planned-from-2025.html