Heat
How Britain heats its homes, and what it would take to stop doing it with gas.
Domestic heat is roughly 17 percent of UK CO₂ emissions. Eighty-five percent of GB homes use a gas boiler. The pathway to decarbonised heat involves three technologies (heat pumps, heat networks, hydrogen) and one binding constraint (pace of installation). This route traces the evidence for each.
06Route 6 of 12 · Energy vectorsAfter this route you will be able to
- Describe the current GB heat mix: gas dominance, fabric condition, boiler replacement rates.
- Name the three decarbonisation technologies and their characteristic costs and timelines.
- Explain how heat-pump coefficients of performance work in a British climate.
- Identify what the 2025 Warm Homes Plan commits to, and what it defers.
- Make a reasoned call on fabric-first versus technology-first approaches.
23 October 2024Warm Homes Plan announced · £13.2 bn over the Parliament
The 2024 Budget allocated £13.2 billion to warm homes, but the binding constraint is how fast homes can actually be upgraded.
The
The Climate Change Committee's
The second number is stock. There are 26 million households with gas boilers. Even at 1 million installations per year, replacing the lot takes 26 years. The policy horizon for net-zero heat runs beyond 2050 on almost any credible delivery pathway.
Money is now allocated. Policy is clear. The technology works. Why is heat-pump rollout still running at a tenth of what the decarbonisation pathway requires, and what binds faster than funding?
The answer is rarely money. It is the fabric of British homes, the workforce that installs heating, and the household-level friction of swapping a gas boiler for something unfamiliar.
Section 01 · The current mix
Four in five homes heat with gas.
GB residential heat is dominated by natural gas. Everything else is a rounding error in the stock today.
Source: DESNZ English Housing Survey 2024, ONS Census 2021, MCS quarterly installation data, HMT Autumn Budget 2024.
Gas boilers dominate because they are cheap to install (around £2,500 fitted), cheap to run at current gas prices, and reliable. The technology has improved steadily (condensing boilers at 90 percent efficiency are mandatory for new installations) but the fuel source has not changed. Decarbonisation means either electrifying heat (pumps), centralising heat (networks), or switching the gas (hydrogen). Those are the three pathways below.
Section 02 · Heat pumps
Three to four units of heat per unit of electricity, in British conditions.
A heat pump moves heat rather than creating it. Its efficiency is measured by Coefficient of Performance (COP) for instantaneous output, or Seasonal Performance Factor (SPF) for a year-round average. British field data now gives a clear baseline.
A well-installed air-source heat pump in a GB home achieves a
Performance drops at low ambient temperature. A 2.8 seasonal average combines milder shoulder months with colder deep-winter periods when COP might fall to 1.8-2.0. Backup resistance heating can absorb this, though at lower system efficiency.
Three factors shape real-world SPF: radiator sizing (heat pumps run at lower flow temperatures, typically 45-55°C rather than 70-80°C, so radiators must be larger), fabric condition (uninsulated homes lose the output faster than pumps can deliver), and commissioning quality (weather compensation curves, flow rates, anti-legionella cycles).
All heat-pump installations eligible for the Boiler Upgrade Scheme grant must be carried out by an MCS-certified installer and must comply with MIS 3005-I, the consumer installation standard for heat pump systems.
Microgeneration Certification Scheme, MIS 3005-I (v7)
Section 03 · Heat networks
Centralised heat, individual billing. Ofgem now regulates.
A heat network delivers hot water or steam from a central source to multiple buildings. They dominate heat provision in some European countries (Denmark 65 percent, Sweden 50 percent) but reach only 2 percent of GB homes.
Heat networks are a good fit for dense urban areas and for large institutional buildings (universities, hospitals, military bases). The economics break down at suburban densities.
Until 2025, GB heat networks were almost entirely unregulated. Consumers on heat networks had none of the protections a gas or electricity customer would have: no price cap, no switching, no ombudsman, no standards of service. The
The new regime introduces price transparency, a consumer protection regime comparable to gas and electricity, mandatory consumer complaints routes through the Energy Ombudsman, and zoning powers that let local authorities designate Heat Network Zones where heat networks are the mandated decarbonisation route.
Common misconception
Heat networks are low-carbon by default.
A heat network is only as low-carbon as its source. The majority of GB heat networks are currently fed by natural gas boilers or CHP and are not low-carbon. Low-carbon heat networks use large air-source heat pumps, ambient loops tied to river water or waste heat, or geothermal. The 2025 Heat Network Regulations introduce a carbon intensity standard that new networks must meet.
Section 04 · The fabric call
Fabric first, or technology first? Pick a deployment philosophy.
The debate about decarbonising GB heat turns on a sequencing question. Do you upgrade fabric first (insulate, draught-proof, replace windows), then install heat pumps on a lower heat load? Or install heat pumps now, accept higher running costs, and improve fabric gradually?
Check your understanding
Three questions on what you have just read.
Key takeaways
- 85 percent of GB homes heat with gas. The pathway to decarbonised heat is heat pumps, heat networks or hydrogen.
- Air-source heat pumps achieve SPF 2.8-3.2 in British conditions, rising to 3.5-4.2 for ground-source.
- Heat networks reach ~2 percent of GB homes. Ofgem has regulated them since 27 January 2025.
- The 2024 Warm Homes Plan allocated £13.2 bn. The binding constraint is deployment rate, not funding.
- The fabric-first vs technology-first debate is the policy sequencing question. The CCC favours fabric first; BUS favours technology first.
References
- DESNZ: Warm Homes Plan
2024 Budget allocation, insulation and heat-pump funding envelope.
Primary policy source.
- Energy Systems Catapult: Electrification of Heat demonstration
742-home UK trial: SPF distributions, installer lessons, commissioning practice.
Primary empirical source for GB heat-pump performance.
- Ofgem: Heat networks regulation
2025 regulatory regime, consumer protection rules, zoning powers.
Primary regulatory reference.
- CCC: Seventh Carbon Budget
Heat pathway, 1 million/year target, fabric-first advice.
Independent pathway analysis.
- Microgeneration Certification Scheme
MIS 3005 installer standard, quarterly installation data.
Installation standard and deployment rate source.
The next route opens nuclear. A 14 percent slice of the generation mix, with four AGR plants retiring by 2028 and Hinkley Point C close to commissioning.