By Nicki - posted on June 23, 2021

Low Carbon Heating

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The Problem

As the race to “net zero” increases in urgency, how we heat our homes becomes ever more critical. Nearly two thirds of the energy we use in our homes today goes into heating, largely supplied by natural gas. New build homes won’t be able to install domestic gas boilers from 2025 and gas boilers are set to be phased out of all homes by 2038. Moving away from this fossil fuel will be an important step in decarbonising – or reducing the carbon emissions – of the domestic energy sector. (Replacing our heating systems is by no means the only way to reduce our home’s carbon footprint – see our article on energy efficiency.)

The Solutions

The field is full of options, from microwave boilers and infrared heaters to geothermal and district heating. The two most talked about technologies right now are heat pumps and hydrogen-ready boilers. There’s no one clear winner, since choosing an appropriate home heating system necessarily depends on a number of factors, including geography, space constraints, cost and occupant behaviour, just to name a few. The choice of heating technology will also hinge on the ability of the current gas and/or electricity grids to adapt to whatever fuel of the future becomes most prevalent.

The three most likely ways to decarbonise our heating are by:

  1. Repurposing the gas grids with a low carbon alternative, for example green hydrogen
  2. Electrification, including storage heaters, heat pumps, infrared heaters, etc.
  3. District heating, where heat from a centralised energy hub is delivered to your home

Biomass and solar thermal, although certainly part of the mix, will probably be more limited.

Green Fuels

Swapping a coal fire for a shiny new heat pump, for example, won’t necessarily help reduce carbon emissions if the electricity delivered to that home is produced by burning coal. We need to take a step back and review what low carbon fuels could power our heating systems of the future.

Electricity

Renewable energy sources, like solar, wind and hydro, can generate electricity without depleting the Earth’s finite resources. (Although controversial, nuclear is also a low-carbon electricity source.) You don’t need solar panels on your roof to take advantage of renewable electricity – just sign up to a green tariff. Our renewable energy article has more information on the nuances of green tariff claims. It also provides further detail about renewable technologies and financial incentives, should you choose to install these.

Hydrogen

This little molecule packs a punch, but not all hydrogen is created equal. It’s a clean energy source because, when burned, hydrogen emits only water vapour. However, its production, storage and transportation can have a big impact on its carbon emissions. ‘Green’ hydrogen uses renewable power to achieve electrolysis by splitting hydrogen from water. ‘Blue’ hydrogen, on the other hand, is made by converting methane (i.e., the main component of natural gas) into hydrogen with an idea to capture and store the emitted carbon dioxide. Carbon capture and storage (CCS) technology, however, is not yet proven at scale and is unlikely to capture 100% of carbon emissions.

Biomass

Biomass is a fancy term for any organic matter – wood, plants, manure, food scraps, etc. Wood burners recently saw a resurgence, with many people choosing this heating system for its environmental credentials. Unfortunately, although burning wood pellets, chips or logs can technically be a carbon neutral heating source, it creates particulate matter pollution, and there is no safe level. A lesser known way to create energy from biomass is using an anaerobic digester. This process breaks down organic matter in the absence of oxygen to create biogas (a mixture of methane, carbon dioxide and trace gases). Farms, wastewater treatment plants and even breweries are perfect candidates for this process. So far, only one UK energy supplier offers a 100% green gas tariff, although several others offer a mix of green gas and carbon offsets. Another UK energy supplier has indicated that its future green gas offer will not include products of animal farming.

Geothermal and waste heat

Naturally-occurring hot reservoirs can be exploited to provide home heating, with some even being used to generate electricity. But it’s a postcode lottery whether you live near a geothermal reservoir. Geothermal energy isn’t the only way to provide district heating, however. Harnessing waste heat, including from industry, data centres, sewage and incineration, and transforming that into space heating maximises the potential of existing low-energy sources that would otherwise be lost.

The pros and cons of low carbon heating technologies

Congratulations! You’ve decided to take the leap into low-carbon heating. But the big question is: what technology do you choose? It’s one that will be driven by policy, availability, personal motivations and household circumstances.

Policy

The cost of converting the mains gas grid to carry hydrogen is likely to be of a similar magnitude to developing a zero-carbon electricity grid. It’s unclear if the gas network can be repurposed and, even if it can, who would be liable for the pre-existing pipework, particularly in people’s homes. Producing a hydrogen-ready boiler isn’t significantly more expensive than a gas boiler, but the complexities of the production, storage and transport of this fuel may limit its use in UK homes. The benefits of green hydrogen will more likely be in industries where portability, storage and energy intensity is critical, such as long haul transport and high temperature industry.

Electrification also comes with its own difficulties. Networks must carefully manage demand, particularly during seasonal heating variations, consider storage and backup solutions. They also have to contend with power quality disturbances from technologies such as heat pumps and (to a lesser degree) electric vehicles.

Ofgem already regulates gas and electricity to ensure consumers are protected. But it doesn’t yet regulate heat networks, so consumers who have district heating have limited protection if things go wrong. (A consultation launched in 2020 proposed to establish Ofgem as the heat network regulator. Feedback is still being analysed.) Bear this in mind if district heating is available to you.

Whilst you might think that decisions on the poles, wires, pipes and protections don’t affect you directly, other potential policy changes certainly will. Electricity is currently about four times the cost of gas per unit energy. There is also little financial help for the “able-to-pay” market towards the capital costs of renewable technologies. So in the current climate, if a household is motivated to switch to a low carbon heating system, like a heat pump, not only would they be out of pocket, their ongoing energy costs would also likely be higher than if they continued using an efficient gas boiler. It’s possible, however, that future decisions could shift the cost-benefit calculations of these different heating technologies. Future pricing of gas and electricity, alongside low carbon heating grants and other incentives, could sway households to adopt low carbon technologies more readily.

Availability

A home’s location will constrain the available heating choices. For example, district heating may rely on sufficient population density, such as in a city centre, to justify its viability. Similarly, remote rural households may not have the option to connect to a mains low carbon gas network. And geothermal energy is limited to certain regions of the country, particularly those areas with hot aquifers.

Building characteristics may also limit options. Energy inefficient (i.e., leaky) homes are typically not suited to heat pumps. Flats in multi-storey buildings likely have low space heating demands so direct electric heating, such as with storage heaters, can be more cost effective than installing heat pumps. Planning permission, smoke control areas and available space (e.g., for hot water cylinders or wood stores) also pose restrictions.

Motivations

Your reason for installing low carbon heating may determine what technology you end up with. If finances, including payback period and lower bills, are the primary driver, grants for the installation of a particular technology and the market price of energy (including the sale of excess energy into the grid) will guide your preference.

Heating systems also have different impacts on levels of comfort, with infrared heaters warming objects whereas convection heaters warming the surrounding air, for instance. Some may be very responsive to changes you make to the settings, whilst others should be left alone as much as possible to maintain a comfortable temperature throughout the day as well as for efficiency reasons.

With today’s spotlight on carbon emissions, you may choose low carbon heating for environmental reasons. Check your energy tariff, insulate your home to make it as energy efficient as possible, then consider swapping out your heating system. It makes more sense to do this if you currently have a coal fire, an oil boiler or a very old non-condensing gas boiler.

Household circumstances

Last, but certainly not least, the choice of heating technology will come down to your personal circumstances – how you prefer to heat you home and when, what heating you currently have and its remaining life expectancy, how much upheaval you’re willing to tolerate and, of course, cost.

The following prompts may help with your decision-making:

  • Do you prefer to heat individual rooms or the whole home?
  • Do you want instant heating or do you want a constant temperature through gradual heating?
  • Where do you spend most of your day? Is it indoors? Do your comings and goings fall into a pattern?
  • Is there a mains gas connection already?
  • Is your home sufficiently insulated?
  • What is the remaining lifespan of your current heating system?
  • Will the new system meet all your heating needs? (Solar thermal, for example, may not.)
  • What are the maintenance requirements?
  • Will the heating system you’re considering require bigger radiators, drilling through concrete floors, pipework on display, etc.? Are you willing to tolerate this disruption and/or aesthetic?
  • How much is the new technology going to cost upfront? Are you eligible for any grants?
  • What are the ongoing energy costs associated with the new technology? Will you save money in the long term? Are you eligible for financial incentives?
  • Are you planning to undertake other building works? This can often be a good time to consider your current and future heating requirements
  • Will the heating technology be standalone or to you intend to use it in combination with another system (e.g., heat pumps and solar PV or storage heaters and battery storage)?

What Next

Once you’ve decided what you want out of your heating system and why, start gathering quotes. Find contractors for low carbon heating products and installations by searching the Microgeneration Certification Scheme (MCS). Find energy efficiency installers who comply with the PAS 2030: 2019 (Publicly Available Specifications standards 2030: from the year 2019) on the TrustMark website. Any grant-funded work must use installers and/or products with these accreditations. If your chosen heating technology doesn’t require accreditation, look for Buy With Confidence installers – these are companies that have been vetted by Trading Standards.

Consider also reading about the following retrofit measures: