In the first two parts of the Hot Topic series, we explored running costs and energy consumption for common UK heating systems. This final section looks at the greenhouse gas emissions involved, using the same 100m² example home.
Emissions are shown as CO2E using the government’s latest conversion factors, which take into account all major greenhouse gases. Electricity figures reflect the current national grid mix, which still includes a large share of gas generation.
Hydrogen Boiler
Pros: No emissions from your building, potential for the future
Cons: Currently costly to run and wastes energy in production
Hydrogen itself burns cleanly but producing it requires a huge amount of electricity. Green hydrogen, made entirely from renewables, has very low emissions, while hydrogen created using grid electricity has very high emissions. Its impact depends entirely on how it is produced.
Oil Boiler
Pros: A practical and widely used choice for properties that aren’t connected to the gas grid.
Cons: Produces some of the highest emissions of any commonly used heating fuel due to the nature of kerosene.
Kerosene is a fossil fuel and has the highest emissions of the fuels compared in this series.
Liquid Petroleum Gas (LPG) Boiler
Pros: A workable heating solution for off-grid homes where other fuels aren’t suitable.
Cons: LPG remains an expensive and carbon-intensive fuel despite its convenience.
LPG is another fossil fuel option, and using it for heating has a large amount of emissions associated with it.
Gas Boiler
Pros: A reliable, accessible and generally affordable heating method with lower emissions than other fossil fuel options.
Cons: Still dependent on a fossil fuel, so it contributes directly to carbon emissions.
Gas boilers are common in part because gas produces fewer emissions than oil or LPG leading to improved air quality.
Electric Storage Heaters
Pros: Straightforward to install and well-suited to smaller, well-insulated spaces where heat demand is modest.
Cons: Running costs climb quickly in larger or draughty homes, especially when powered by grid electricity that still includes a significant gas contribution.
Electric heating only becomes low-emission when powered by clean electricity. As much of the UK grid still relies on gas, emissions for storage heaters currently sit close to gas heating. A renewable tariff helps push the grid in the right direction towards net zero.
Electric Infrared Heaters
Pros: Inexpensive to install and effective for heating specific areas rather than whole rooms, helping keep energy use down when managed properly.
Cons: Poor use can lead to cold spots, condensation and damp issues, particularly in buildings heated intermittently.
Infrared heaters operate at almost 100% efficiency and use less energy because they are easy to target. Problems arise when buildings are under-heated, leading to cold spots, condensation and mould, especially when users switch them on only when inside the building.
Air Source Heat Pumps
Pros: Capable of delivering lower running costs than gas when well-installed, with government grants available to support the upfront investment.
Cons: Installation is costly and performance can dip in very cold conditions, so not every home will achieve the same level of efficiency.
Heat pumps create far more heat than the electricity they consume, so their emissions are much lower than boilers or resistance heating. This efficiency is a major reason behind the government’s net-zero strategy.
Ground Source Heat Pumps
Pros: Extremely efficient with low energy consumption thanks to the stable temperatures beneath the ground.
Cons: Installation can be expensive and complex, often requiring extensive groundwork that limits where they can be used.
Ground source systems use even less electricity than air source models, resulting in lower emissions. However, cost and installation requirements limit where they are suitable.
Log Burner
Pros: Can be relatively inexpensive to fuel and works well in off-grid settings.
Cons: Delivers heat to a limited area and is less efficient than modern whole-house heating systems.
In theory, emissions can be lower than heat pumps at present because sustainably sourced wood can have its carbon reabsorbed over time. However, log burners are inefficient, heat only small spaces and rely on forestry that cannot scale nationwide.
Biomass Boiler
Pros: A renewable heating option with running costs that compare favourably to fossil fuel systems.
Cons: Requires dedicated storage space and regular fuel deliveries and isn’t suitable everywhere due to fuel supply and sustainability considerations.
Biomass boilers currently have the lowest operational emissions because their carbon cycle is relatively short. They still produce other greenhouse gases, require significant fuel storage and depend on sustainable forestry that cannot meet UK-wide demand. They are effective where waste wood is plentiful, but not a scalable national solution.
Summary
The direction of government policy becomes clear when you consider emissions. Electricity offers the best pathway to net zero because it can be fully decarbonised. Heat pumps reduce overall energy demand and generate far fewer emissions, making them the strongest large-scale option available today. Other technologies will still have their place, but heat pumps remain the most practical route for households aiming to cut their carbon footprint.