Heat network efficiency – what gets measured gets managed

Sepideh Kiarsi, Energy Consultant, Insite Energy.

The potential of heat networks to reduce carbon emissions is strong on paper. In fact, if the UK is to meet its 2050 net-zero carbon deadline, it’s estimated around 18% of our heat supply must come from communal or district heating – up from 2% in 2018. It’s why the government is supporting the development of heat networks through new funding and regulatory programmes.

However, heating systems are only as good as they are built, operated and maintained. To optimise them, you need to know how efficient they really are – and that means it needs to be measured.

Accurate usage data is particularly critical for heat networks, where landlords are responsible for setting accurate customer heat tariffs. Residents on communal heating schemes don’t get a say about how much they pay for their heating; they are locked in, with no possibility to switch supplier. Pricing transparency is therefore vital to avoid potential conflict and complaints. For various reasons, some customers will simply refuse to pay, leading to higher than budgeted debt and reduced cashflow for a scheme. Heat providers may then increase residential tariffs to cover the higher level of debt contingency, exacerbating the situation for those customers in fuel poverty who are actually paying. It’s a ‘catch 22’ scenario.

Performance data is also crucial for any issues to be quickly pinpointed and rectified and to help avoid the generation of surplus heat energy resulting in higher bills and emissions. This is particularly important in combined heat and power (CHP) or biomass schemes where industry standard figures are unreliable. If your heat network is operating at 50% efficiency, an incoming fuel tariff of 3p/kWh can easily translate to at least 6p/kWh or more likely 9p/kWh for the end user. Without knowing the source of an issue, through measures such as check meters, which can break a network down into different identifiable areas, resolving them becomes a major feat, which could be disruptive to customers.

For all these reasons, the need for accurate usage and performance data was recognised in the Heat Network (Metering & Billing) Regulations of 2014, and again, most recently, in the Chartered Institute of Building Services Engineers (CIBSE) Code of Practice for the UK (CP1 2020). Both state that buildings containing multiple dwellings/units shall also be metered at the heat exchanger or point of entry into that building.

Yet, too often, the importance of check meters is overlooked or misunderstood and the guidance is not followed. Across the circa 250 heat networks for which Insite Energy manages the metering and billing, dataloggers show only around 20% have at least one check meter connected. This is a false economy, given a check meter costs a few hundred pounds to procure and install – a negligible amount compared to the overall cost of a development.

Even where check meters are installed, they are frequently insufficiently reliable to be used in place of industry standard efficiency ratings. Frustratingly, this is often due to something as simple as the incorrect labelling of the meter. It’s not clear what the data refers to, or it is inaccessible or wrongly wired. By the time a building is fully occupied and the energy or finance team of the housing association or managing agent needs to access the data, the developer has long gone. 

By installing check meters, the heat network’s performance can be monitored to evaluate its efficiency. An efficient heat network will use less energy and both heat suppliers and customers will pay less.

Installation of correctly labelled, fully functioning check meters to measure the efficiency of each heat generator in a plant room should be mandatory. Ideally, this would extend to check meters after the heat exchanger and at the entrance to each building block. Meters should be regularly serviced and recalibrated for accuracy and replaced at the end of their life (ten to 12 years for older models, up to 16 years for newer).

The first step is to conduct a site survey, via a qualified engineer, to ascertain what metering is already in place and in use (your metering supplier should do this for you as part of their service), before making sure any new or existing solution is usable and reliable.

So far, the government – keen to avoid any barriers that might impede the growth of heat networks – has stopped short of mandating check meters. However, there’s a fine line between incentive and disincentive, particularly when a lack of enforcement impairs performance, undermining credibility, and confidence.

When government attention does, inevitably, turn to system efficiency – no doubt driven by consumer concerns over tariffs and the ever-more-urgent need to meet carbon targets – housing providers that already have these meters in place will be ahead of the curve and free from the inconvenience of large-scale meter retrofit projects. The cost of running a heat network always matters, but as time goes by it will be even more important to keep the operation cost low to assure customer satisfaction.