Ambient heat networks, sized and costed on what the numbers will back.
Ambient (5th-generation, low-temperature) networks share low-grade and waste heat across buildings, with a heat pump lifting the supply at each connection. The hard part is the system design: which sources, what loop temperature, where the heat pumps sit, and whether the numbers beat a conventional network. Sympheny models and optimises exactly that, so the scheme you take to a funder is the one the figures support.
Every optimised anergy-network combination plotted on cost against carbon, from a single project.
Heat network zoning sets where. It does not settle the system inside the loop.
The source decides everything, and it is local
Data centres, supermarkets, industry, sewage, groundwater. The sources an ambient loop can draw on, their seasonal limits and their temperatures are specific to the site, and they set the ceiling on what the network can deliver. Get the source assessment wrong and the rest of the concept rests on sand.
It fits the funding rules, if the design is right
Heat network zoning under the Energy Act 2023 designates where a network is the lowest-cost low-carbon route, and the Green Heat Network Fund successor expects low-carbon sources such as heat pumps, waste heat and geothermal. Ambient loops are well suited to all of that. Whether a given scheme actually qualifies comes down to the source mix and the network design underneath.
Spreadsheets cannot hold the trade-offs
Loop temperature, source mix, decentralised heat pumps and seasonal storage all trade against each other on cost and carbon. Testing a handful of combinations by hand misses the design that wins, and with Ofgem now regulating heat networks against technical standards, a funder or an assessor wants to see the comparison, not just the conclusion.
Proven on ambient and low-temperature networks.
A low-temperature thermal network supplied by river and groundwater, sized across six energy hubs and stress-tested against more than 30 future price and demand scenarios for the Insel-Holligen district.
Read case study26 buildings modelled as one multi-temperature system, with low-temperature sources feeding heat pumps and seasonal borehole storage validated for the campus's 2030 climate-neutral concept.
Read case studyA city-wide supply strategy showing a CO₂-free system is reachable at similar life-cycle cost to the existing fossil-based one, with ambient and renewable sources in the mix.
Read case studySources, network and architecture in one optimisation.
Sympheny models the ambient loop, the heat sources and the building-level heat pumps as one multi-energy system, then optimises the whole thing at hourly resolution. The comparison is consistent because it comes out of a single model rather than three separate studies stitched together, and every candidate source, loop temperature and storage option is weighed on the same basis.
The network is part of the model, not an assumption.
Define hubs (buildings, zones or substations) and draw the ambient loop between them on a real GIS map, with heat loss and cost per metre. Because the loop runs near ground temperature, the model captures the low losses that make 5GDHC attractive, and the routing cost feeds straight into the technology comparison.
- Ambient, low-temperature and conventional network types modelled between the same hubs
- Network length and routing cost measured directly from the GIS map
- Bidirectional heat exchange between buildings represented in the energy balance
Every ambient source, evaluated as a candidate.
Groundwater, river and lake water, wastewater, data-centre and industrial waste heat, and borehole fields all enter the same optimisation as candidate sources, each with its seasonal availability and temperature. Decentralised heat pumps lift the loop to delivery temperature, modelled with seasonal COP profiles so winter performance is real, not a single annual figure.
- Groundwater, surface water, wastewater, waste heat and boreholes as candidate sources
- Seasonal resource limits respected, so the optimisation stays physically honest
- Decentralised heat-pump COP profiles, month by month
Ambient loop, low-temp or conventional. Let the optimisation decide.
Instead of fixing the network temperature before modelling starts, define the options as candidates between the same hubs. The optimiser weighs an ambient 5GDHC loop against a low-temperature or conventional network on cost and carbon together with the source mix and storage. You get the answer, with the trade-off shown, rather than another assumption to defend.
- Ambient (5GDHC), low-temperature and conventional architectures in the same project
- Seasonal and short-term storage, including boreholes, sized by the optimiser
- Heating and cooling resolved together across a full reference year
Pareto cost and carbon comparisons stakeholders can read.
Every combination the optimiser evaluates lands on a Pareto front: life-cycle cost against CO₂. The cheapest scheme, the lowest-carbon scheme and the trade-offs between them, all from one project. Load-duration curves, Sankey flows and hourly profiles sit alongside it, and the underlying data exports to Excel for the business case.
- Pareto front across every optimised anergy-network scenario
- Hourly resolution across a full reference year, heating and cooling
- Stakeholder-ready charts and an Excel export of the underlying numbers
For the economic buyer: a fundable scheme, with the cost of each level of ambition made explicit and the evidence base a Green Heat Network Fund application needs, where the low-carbon source case is set out alongside the cost against CO₂ across more than 50,000 technology combinations per run.
Sympheny covers feasibility and concept design: the stage where the source mix, loop temperature, storage and business case get settled. It is not the zoning assessment tool that designates the network, and it is not detailed hydraulic design (pipe sizing, pressure and flow modelling), which is a separate step in tools built for it. Most of what decides whether an ambient network gets funded happens before that stage.
Why an optimisation model, not another spreadsheet.
Anergy networks are a multi-energy, multi-temperature problem. The tools most teams reach for were built for something narrower.
Versus spreadsheets
A spreadsheet can size one configuration. It cannot search the source mix, network temperature, storage and building technologies together, and it cannot show a funder the cost-versus-carbon trade-off across the whole option space.
Versus single-energy desktop tools
Tools that size a heat network or a heat pump in isolation miss the point of 5GDHC, where heating, cooling and inter-building heat recovery are one balance. Sympheny optimises electricity, heat and cooling together.
Versus building it from research code
The optimisation comes from a decade of Empa and ETH Domain research, already packaged as a cloud platform with GIS, scenario comparison and client-ready outputs. You get the method without maintaining a solver yourself.
Questions UK delivery teams and authorities ask.
What is an anergy or ambient heat network?
An ambient heat network distributes heat at very low, near-ground temperature, so each connected building uses its own heat pump to lift the supply to the temperature it needs. Because the loop runs close to ambient, distribution losses are minimal and the same network can move heat from buildings that are cooling to buildings that are heating. Anergy network is the term common in Switzerland; in the UK the same idea is usually called an ambient loop or a 5th-generation district heating and cooling (5GDHC) network.
How does an ambient network fit UK heat network zoning?
Heat network zoning under the Energy Act 2023 designates the areas where a heat network is the lowest-cost low-carbon route, and within a designated zone connection can become mandatory. Zoning decides where; it does not settle the source mix, loop temperature or cost. An ambient loop is one of the architectures that can serve a zone, and Sympheny models and optimises the energy system inside it so the scheme can be justified to the authority and the funder.
Does an ambient network qualify for the Green Heat Network Fund?
The Green Heat Network Fund successor supports the construction and expansion of low-carbon heat networks in England and expects low-carbon sources such as heat pumps, waste heat and geothermal. Ambient loops are built around exactly those sources, so they fit the direction of the scheme. Whether a given scheme qualifies turns on the evidenced source mix and network design. Sympheny produces that evidence base: sources and network compared on cost against CO₂, with the underlying data exportable for the application.
Which heat sources suit an ambient network in the UK?
Low-grade and waste-heat sources that are available locally: data centres, supermarkets, industry, treated sewage, groundwater and the ground itself through borehole fields. The right mix depends on what the site offers and on each source's seasonal availability and temperature. Sympheny models these as candidate sources in the optimisation, so the source assessment and the network design are decided together rather than in sequence.
Do ambient networks fall under Ofgem regulation?
Ofgem became the heat network regulator on 27 January 2026, and networks must register and meet technical standards under the Heat Network Technical Assurance Scheme (HNTAS). That makes a defensible, auditable concept more important, not less. Sympheny returns a sized scheme with the cost-versus-carbon trade-off shown across the option space, so the chosen design can be evidenced against the alternatives rather than asserted.
Where does Sympheny fit in the planning process?
Sympheny is for feasibility and concept design: comparing sources, loop temperatures, storage and the business case before capital is committed. It is not a hydraulic detailed-design tool; pipe sizing, pressure and flow modelling come afterwards in software built for that. Most of the decisions that determine whether an ambient network gets funded are made at the concept stage Sympheny supports, and a first model stands in hours rather than weeks.
Related planning topics and proof.
See your ambient network options compared before you commit.
Bring a site to a demo and watch the sources, loop temperatures and costs compared in one model, or start a free trial and build the first concept yourself.