Are gas boilers compatible with efforts to combat climate change?

In 2019, in France, gas and oil-fired boilers were among the most carbon-intensive heating methods on the market.

For the same amount of heat consumed, a gas boiler emits 35% more greenhouse gases than a Joule electric heater and 4.5 times more than a heat pump[1][2].

This comparison is based on official figures available in the ADEME carbon database[3]. More technically, these are called “emission factors” and are used to convert a physical quantity, such as kilowatt-hours, into an equivalent quantity of greenhouse gases. Analyzing these factors allows us to rank the carbon impact of different heating methods (oil-fired boiler, gas-fired boiler, electric Joule heating, district heating, heat pumps, or wood-fired boilers) and conclude that gas and oil heating solutions are among the highest-carbon options available on the market[4].

Heating oil must be completely phased out of the sector’s energy mix within 10 years, as outlined in the National Low-Carbon Strategy[5]. This government strategy is designed to plan the decarbonization of various sectors (construction, transportation, industry, etc.) by allocating them a maximum carbon budget that decreases over time.

What do energy emission factors include?

Emissions factors are not limited to direct emissions but take the entire life cycle into account.

The emission factor for the natural gas includes emissions from gas combustion (CO2 emitted directly into the atmosphere) as well as so-called “upstream” emissions (fuel extraction, transportation, and distribution, etc.).

The emission factor for electricity for heating includes emissions related to electricity generation, upstream activities (fuel extraction, transportation, etc.), and distribution losses. The method used to calculate this emissions factor treats heating as a “100% seasonally adjusted” use. As such, it takes into account the fact that electric heating requires a different (and higher-carbon) generation mix than the one used to meet the “base load” of electricity consumption in France. In summary, the carbon impact of “peak electricity demand” is fully accounted for in the electricity emissions factor for heating. By way of comparison, the emissions factor for grid electricity in France in 2018[6] was 57 gCO2e/kWh, compared to 147 for heating alone.

What does the future hold for gas-fired boilers?

Horizon 2030:

The government’s Multi-Year Energy Plan[7] projects that biomethane will account for 7% of the gas grid by 2030. For its part, GRDF outlines a very ambitious scenario (one of three distinct scenarios) that projects 30% of biomethane injected into the network by 2030. Setting aside the realism of such a projection, the emissions factor for natural gas would rise to 200 gCO2e/kWh[8] and would therefore still be 25% higher than the current emissions factor for electricity used for Joule heating. By 2030, gas-fired boilers will thus remain one of the most carbon-intensive heating methods on the market, despite such a high penetration of biomethane in the network.

Horizon 2050:

Today, it is the second-most-consumed form of energy in buildings, behind electricity, Gas will rank last in 2050 According to the National Low-Carbon Strategy: 35 TWh, or 7% of energy consumption, compared with 210 TWh, or 27%, today. To achieve this, Several million homes currently heated by gas will have to replace their boilers with lower-carbon heating solutions : heat pumps, district heating systems, wood-fired boilers…

It is important to understand that natural gas cannot be “100% renewable” by 2050 (composed entirely of biomethane[9]) as called for by the National Low-Carbon Strategy, as long as consumption volumes have not been drastically reduced: Gas consumption in the building sector is expected to decrease by a factor of 6 between 2015 and 2050. Achieving France’s goals for the building sector depends on a significant improvement in the energy performance of the existing building stock, as well as on the decarbonization of energy sources. This article focuses on the latter point, without neglecting the former, which is essential and a top priority.

The teams from the Construction and Real Estate Division and the Energy Division

[1] Propane and butane have a slightly higher carbon footprint than natural gas from the utility grid. A few rare district heating systems have a higher carbon footprint than heating oil. Generally speaking, district heating systems are becoming significantly more carbon-neutral by incorporating renewable energy into their energy mix. The current average carbon footprint of district heating systems is 100 gCO2e/kWh and can reach as high as 384. [2] A system that captures “free” heat from the air or ground using an electric pump [3] http://www.bilans-ges.ademe.fr/fr/accueil [4] See note 1 [5] December 2018 draft: This document updates the SNBC so that the carbon targets set for each sector are consistent with France’s goal of carbon neutrality by 2050 [6] ADEME carbon database: “electricity – average consumption mix” [7] Energy transition management tool for France [8] See the box “To learn more…about biomethane!” ” [9] The potential sources under consideration are primarily agricultural (manure, liquid manure, and catch crops). Contrary to some common misconceptions, vegetable peels from household waste will not be sufficient to replace the fossil gas that powers our boilers!