HWB - Council Directive 92/42/EEC

What HWB is and why it matters

The Hot-Water Boilers Directive (HWB) — formally Council Directive 92/42/EEC on efficiency requirements for new hot-water boilers fired with liquid or gaseous fuels — was one of the EU’s earliest pieces of energy-efficiency legislation for heating appliances. It set minimum efficiency requirements that new boilers had to meet before they could be placed on the market, and it tied that efficiency to CE marking and conformity assessment. For a manufacturer or importer of heating equipment, HWB historically defined the baseline a boiler had to clear to be sold lawfully across the Union.

HWB matters today mostly because of how it fits into the wider picture. It was an early, single-purpose efficiency law: it pushed inefficient appliances off the market and introduced a comparative star-rating that let buyers and specifiers gauge a boiler’s performance. But the regulatory landscape has moved on. Its substantive requirements have, in practice, been overtaken by the Ecodesign framework (Directive 2009/125/EC) and the Energy Labelling implementing measures for space heaters and water heaters. Understanding HWB therefore means understanding both what it required and why most of its work is now done by newer instruments.

📄 Official text: Council Directive 92/42/EEC on efficiency of hot-water boilers — on EUR-Lex →

Who HWB applies to

HWB applies to economic operators placing new hot-water boilers on the EU market, with duties scaling by role:

Manufacturers — anyone who makes a hot-water boiler fired with liquid or gaseous fuels, or who has it made and markets it under their own name or trademark. They carry the core obligations of meeting the efficiency requirements, running conformity assessment and affixing the CE marking.
Importers — businesses bringing boilers from outside the EU into the Union market, responsible for ensuring the products they place on the market meet the Directive’s requirements.
Distributors — wholesalers and retailers further down the chain, who handle and supply boilers and should confirm that required markings and documentation are present.

The Directive is aimed at new boilers with a rated output between 4 and 400 kW, fired with liquid or gaseous fuels. It excludes certain appliances from its scope, such as boilers able to be fired by different fuels including solid fuels, instantaneous water-heating appliances, and certain combined heat-and-power and back-boiler arrangements. Boilers covered by other regimes — and, increasingly, by Ecodesign implementing measures — are handled under those frameworks instead.

Key dates and timeline

1992 — Council Directive 92/42/EEC was adopted, setting efficiency requirements for new hot-water boilers and introducing CE marking and the star-rating system.
Subsequent years — the Directive was amended and aligned with later horizontal measures, including the integration of CE marking provisions and adaptation to the broader Ecodesign framework.
From 2013 onward — Ecodesign and Energy Labelling implementing regulations for space heaters and water heaters began to apply, progressively setting the binding minimum efficiency and information requirements that now govern these products in practice. As a result, the operative efficiency thresholds for the products HWB once addressed are today found in those measures rather than in 92/42/EEC itself.

Core requirements

Efficiency requirements

At the heart of HWB are minimum useful efficiency requirements expressed at both rated output (full load) and at part load. A boiler had to achieve defined efficiency levels — depending on its type and rated output — to be placed on the market. This was the Directive’s central mechanism: appliances that fell below the threshold simply could not be sold. The requirement applied across the 4 to 400 kW band the Directive covers, with the efficiency values set against the boiler’s average water temperature.

CE marking and conformity assessment

A boiler covered by HWB had to carry the CE marking as the visible sign that it met the Directive’s requirements, and the manufacturer had to complete a conformity assessment procedure before placing it on the market. The CE marking and conformity provisions were aligned with the EU’s general approach to product legislation, meaning the same modular logic used elsewhere — type examination followed by production-stage controls — applied here. The manufacturer also had to draw up the supporting documentation demonstrating that the efficiency requirements were met.

The star-rating system

HWB introduced a now-historic star-rating scheme. Boilers exceeding the basic efficiency requirements could be awarded efficiency stars — more stars indicating better performance against the reference levels set in the Directive. The rating was a voluntary comparative label layered on top of the mandatory minimum, giving the market a simple way to distinguish higher-efficiency appliances. In practice this early labelling idea has been superseded by the EU energy label introduced under the Energy Labelling implementing measures for heaters, which provides a far more detailed and standardised consumer label.

Relationship to Ecodesign and Energy Labelling

This is the most important point for anyone assessing compliance today. The efficiency-setting role HWB once played has largely been taken over by the Ecodesign Directive (2009/125/EC) and its product-specific implementing regulations for space heaters and water heaters, together with the corresponding Energy Labelling measures. Those instruments set the binding minimum efficiency requirements, the information and documentation obligations, and the energy label that now apply to the heating appliances in this space. HWB remains the originating instrument and part of the legislative history, but for a product on the market now, the operative requirements are typically found in the Ecodesign and Energy Labelling regulations rather than in 92/42/EEC.

Obligations by role

Manufacturers — ensure boilers meet the applicable efficiency requirements, complete conformity assessment, affix the CE marking and hold the supporting documentation; in practice, check the relevant Ecodesign and Energy Labelling implementing measures for the binding current requirements.
Importers — verify the manufacturer’s compliance, ensure CE marking and documentation are in place, and refuse products that do not meet the requirements.
Distributors — handle and supply boilers with due care and check that required markings and documents are present.

Enforcement

Each Member State designates the authorities responsible for market surveillance of energy-using products. In Denmark, the Danish Energy Agency (Energistyrelsen) and the Danish Safety Technology Authority (Sikkerhedsstyrelsen) are involved in the surveillance and enforcement of Ecodesign and energy-labelling rules for heating products, which is where the operative requirements now sit.

Consequences for non-compliance are set at national level and can include orders to stop sales, withdrawal of non-compliant products and penalties. Because efficiency and labelling for heaters are now governed by directly applicable EU regulations under the Ecodesign and Energy Labelling framework, surveillance authorities can act consistently across the Union, and a finding in one market can prompt action elsewhere.

Getting compliant

Confirm whether your boiler falls within the 4 to 400 kW scope and the liquid/gaseous-fuel definition HWB addresses.
Crucially, identify the current operative requirements: check the relevant Ecodesign and Energy Labelling implementing regulations for space heaters and water heaters, which set today’s binding efficiency and labelling obligations.
Meet the applicable minimum efficiency requirements at full and part load.
Complete conformity assessment and affix the CE marking.
Prepare and retain the technical documentation demonstrating efficiency.
Apply the correct EU energy label and product information under the Energy Labelling measures where they apply.

How Conphora helps

Conphora monitors HWB and, just as importantly, the Ecodesign and Energy Labelling measures that now carry its requirements, mapping your boilers against the rules that actually apply today. The platform flags gaps in efficiency, CE marking, documentation and labelling, helps you generate and keep the right records, and alerts you when obligations change so your compliance stays current.

See how Conphora works · Start free with Conphora

Sources and further reading

This guide is for general information and is not legal advice.

Last updated: 12 June 2026