Regulation (EU) No 813/2013, in the form published on legislation.gov.uk for Great Britain, sets ecodesign requirements for space heaters and combination heaters with a rated heat output of up to 400 kW. From 26 September 2015 most boilers up to 70 kW must reach 86% seasonal space heating efficiency, and from 26 September 2018 gas boilers must emit no more than 56 mg/kWh of nitrogen oxides.

What the regulation covers

Article 1 says the Regulation establishes ecodesign requirements for placing on the market and putting into service space heaters and combination heaters with a rated heat output of 400 kW or less. Combination heaters are the boilers commonly called combis, which provide heating and hot water. The Regulation does not apply to several categories, including heaters using solid fuels, heaters that only provide hot drinking or sanitary water, and heaters designed for gaseous or liquid fuels made predominantly from biomass. The text on legislation.gov.uk is the version that applies in Great Britain, so this guide covers England, Scotland and Wales only.

Minimum space heating efficiency

Annex II sets minimums that took effect on 26 September 2015. Fuel boiler space heaters and combination heaters with a rated output of up to 70 kW must reach a seasonal space heating energy efficiency of at least 86%. There is a lower figure of 75% for two categories of type B1 boilers, which are natural draught boilers connected to a shared flue: those up to 10 kW and combination versions up to 30 kW. For larger fuel boilers, above 70 kW and up to 400 kW, the useful efficiency must be at least 86% at full output and at least 94% at 30% of the rated output. How these figures relate to the labelled bands is explained in the guide to boiler efficiency ratings.

Water heating efficiency for combi boilers

Combination heaters also face a floor on water heating energy efficiency, which depends on the declared load profile, a measure of the hot water draw-off pattern the boiler is designed for. From 26 September 2015 the minimums ran from 22% for the smallest profiles to 32% for the largest. From 26 September 2017 they rose, with 32% for the smallest four profiles, 36% for M, 37% for L, 38% for XL, 60% for XXL and 64% for the 3XL and 4XL profiles. A combi designed for high hot water demand therefore has to meet a tougher standard than one designed for a small flat.

The nitrogen oxide limit

From 26 September 2018, emissions of nitrogen oxides, expressed as nitrogen dioxide, must not exceed 56 mg/kWh of fuel input, measured on gross calorific value, for fuel boiler space heaters and combination heaters using gaseous fuels. The limit for those using liquid fuels is 120 mg/kWh. Those figures are set out in the Annex alongside separate limits for cogeneration and heat pump heaters with combustion. The recitals explain that the Commission identified nitrogen oxides as a significant environmental aspect for heaters using fossil fuels, while deciding not to set requirements for carbon monoxide, particulates or hydrocarbons because no suitable measurement methods existed at the time.

Sound limits apply to heat pumps

The sound power level limits in Annex II apply to heat pump space heaters and heat pump combination heaters, not to gas boilers. For a heat pump up to 6 kW the indoor limit is 60 dB and the outdoor limit is 65 dB, with higher figures for larger outputs. A boiler buyer comparing options with a heat pump should therefore not expect the same noise rules to appear on a gas boiler datasheet. The wider comparison is in the guide to heat pump or replacement gas boiler.

Information that must accompany the boiler

Annex II, point 5, requires instruction manuals for installers and end users, and the free access websites of manufacturers, importers and their authorised representatives, to contain the technical parameters set out in the Regulation’s tables, any specific precautions for assembly, installation or maintenance, and information on disassembly, recycling or disposal at end of life. For type B1 boilers the manual must carry a standard warning that the boiler is intended to be connected only to a flue shared between several dwellings in existing buildings, and that any other use would mean higher energy consumption and running costs. An installer or householder can use those documents to check the declared efficiency and installation conditions of a particular model.

What this means when buying

These are product rules on the placing on the market of boilers, so a new boiler sold in Great Britain should already meet the efficiency and emissions floors. They do not replace the separate building regulation for combi replacements in England, covered in the guide to Boiler Plus, or the reasons condensing technology became standard, explained in the guide to condensing and non-condensing boilers. A householder can ask the installer for the manufacturer’s technical parameters for the quoted model.

FAQs

Does the 86% figure apply to every boiler?

It applies to most fuel boilers and combination boilers up to 70 kW. Annex II sets 75% for certain type B1 boilers, and different measures for boilers above 70 kW.

Is the NOx limit the same for oil boilers?

No. Annex II sets 56 mg/kWh for gaseous fuels and 120 mg/kWh for liquid fuels, both measured on gross calorific value.

Does this regulation cover Northern Ireland?

This guide relies on the version published for Great Britain, so it covers England, Scotland and Wales only.

The bottom line

Regulation 813/2013, as it applies in Great Britain, requires most boilers up to 70 kW to reach 86% seasonal efficiency, sets minimum water heating efficiencies for combis and limits NOx emissions from gas boilers to 56 mg/kWh. It also requires installer and user manuals to carry specified technical information. This is general information, not regulated advice on any specific installation.

Sources

This guide draws on the following primary sources, current as of 24 September 2026:

• legislation.gov.uk, “Commission Regulation (EU) No 813/2013: ecodesign requirements for space heaters and combination heaters”
• legislation.gov.uk, “Commission Regulation (EU) No 813/2013, Annex II: Ecodesign requirements”

Related guides

Best Boiler Deals is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not regulated advice on any specific installation — always confirm the details with a Gas Safe registered engineer.