Part one of this two-part series, explained the impact of hydrogen on current appliances in the home and how the performance will vary depending on appliance and blend percentage. The article cites several studies done on natural gas appliances proving that appliances can only withstand up to a 20% hydrogen-natural gas blend. 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.
  1. 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.