Best Heat Loss Software UK (2026): 4 Tools Compared
The best heat loss calculation software for UK installers in 2026 — Heatpunk, Heat Engineer, Spruce, Vento and free calculators compared on method, MCS, design and price.
By Max Tuleberg · Founder, Vento · Last updated 25 October 2026
Founder of Vento. Worked on the tools before building the software.
The best heat loss software depends on what comes after the calculation. If you design air-to-water heat pumps for MCS, pick a dedicated heating design tool — Heatpunk, Heat Engineer or Spruce. If you install air conditioning or air-to-air heat pumps, pick one that carries the load into the system design and the quote — that's what Vento is built for. Here are the four tools UK installers most often shortlist, compared on method, what they design afterwards, MCS paperwork and pricing. Reviewed October 2026.
| Tool | Best for | Method its site states | Designs afterwards | MCS documents | Pricing published |
|---|---|---|---|---|---|
| Vento | Air-con and air-to-air heat pump installers | Room by room to CIBSE design conditions; a simplified MCS-style estimate for air-to-water | Split and multi-split air-con; air-to-water scoping (radiators, cylinder, schematic) | Readiness check only | Yes |
| Heatpunk | Air-to-water design to MCS standards, with a free tier | Room by room; cites CIBSE, MCS and BS EN 12831 | Radiators, underfloor heating, flow temperature, hot water | Yes | Yes |
| Heat Engineer | Heating designers — heat pumps, boilers and hybrids | Room by room; cites CIBSE Guide A and BS EN 12831-1 | Emitters, pipes and pumps, with CAD drawings | MCS performance estimate | Yes |
| Spruce | MCS heat pump businesses that want the paperwork handled | Cites MCS and CIBSE guidelines; room-by-room not stated | Emitters, cylinder and pipework | Quality management system, DNO forms, handover packs | No — book a call |
1. Heatpunk — best free start for air-to-water design
Heatpunk takes a floor plan, works out the heat loss room by room and designs the wet system — radiator and underfloor sizing, flow temperature and hot water — then produces the MCS documents the job needs. The free tier makes it the easiest place to start, with paid plans adding features such as e-signed proposals. Best for: air-to-water heat pump installers who want MCS-standard design without a big upfront cost. Vento vs Heatpunk.
2. Heat Engineer — best for depth of heating design
Heat Engineer is one of the deepest heating design toolsets in the UK: several survey capture methods, CAD drawings, emitter, pipe and pump sizing, an MCS heat pump performance estimate and digitally signed proposals. It covers boilers, biomass and hybrid systems as well as heat pumps. Best for: heating designers who need detailed wet-system design across technologies. Vento vs Heat Engineer.
3. Spruce — best for MCS paperwork
Spruce pairs heat loss and emitter, cylinder and pipework design with the paperwork around an MCS install: a built-in quality management system, DNO applications and handover packs. It integrates with job systems rather than including its own, and doesn't publish its pricing. Best for: MCS heat pump businesses where the admin is the bottleneck. Vento vs Spruce.
4. Vento — best for air conditioning and air-to-air heat pumps
Vento runs a room-by-room heat load as you survey — heat loss for winter and cooling load for summer, to UK design conditions — and carries it straight into unit selection, a scaled split or multi-split design, the proposal the customer e-signs and the F-Gas record. It also sizes air-to-water systems (radiator output at your flow temperature, the cylinder and a system schematic), but as a scoping estimate rather than a full MCS heat loss for the design pack. Pricing is flat per tier, from £39 a month billed annually. Best for: air-con and air-to-air installers who want the sizing to become the design and the quote. Vento's heat loss software.
Free options
MCS publishes its own free MCS Heat Load Calculator, which picks design conditions from the postcode and is built around the standard MCS installs are designed to. For a quick check without an account, our free room-by-room heat loss calculator gives watts per room, the total in kW and the radiator output each room needs at your flow temperature. For cooling, use the air conditioning size calculator. Neither needs a signup.
How to choose
- Is the heat loss going into an MCS design pack? Use a tool built to MCS's design requirements — see how to do a room-by-room heat loss calculation.
- Is it a Boiler Upgrade Scheme job? Then the heat load must meet MIS 3005-D — air-to-air included. Vento's sizing is for design and quoting; check the calculation you submit meets the standard.
- Is the system wet or refrigerant? Radiators and cylinders are a different design problem from indoor units, condensers and pipe runs. Pick the tool built for the one you fit.
- Do you need cooling loads too? Air conditioning and air-to-air heat pumps are sized on both heating and cooling — most wet heat pump tools only do the first.
- What happens after the design? If you also want the proposal, deposit, scheduling and service on the same record, check whether the tool includes job management or expects you to integrate one.
Many firms that do both wet and air-to-air work use one of each. For the wider picture, see the best heat pump software and best air conditioning software guides.
This guide is general information for UK installers, not legal or regulatory advice. Always check the current regulations and manufacturer instructions for your specific job.
Frequently asked questions
What is the best heat loss software in the UK?
It depends on what you install. For air-to-water heat pumps where the heat loss has to stand up in an MCS design pack, dedicated heating design tools such as Heatpunk, Heat Engineer and Spruce are built for the job. For air conditioning and air-to-air heat pumps, Vento runs the room-by-room load as you survey and carries it straight into unit selection, split and multi-split design and the proposal.
Is there free heat loss software?
Yes. Heatpunk has a free tier, and Vento's room-by-room heat loss calculator is free with no signup — it gives watts per room, the total in kW and the radiator output each room needs at your flow temperature.
Does heat loss software need to follow BS EN 12831?
For a heat pump installed under MCS — and so for the Boiler Upgrade Scheme — yes. MCS's heat pump design standard, MIS 3005-D, requires the heat load to be calculated to BS EN 12831-1:2017, with losses for each room, and that applies to air-to-air heat pumps as well as air-to-water. A quick estimate is fine for scoping a job, but not for the design.
What's the difference between heat loss and heat load?
Heat loss is the heat a room loses in winter, which a heating system has to replace. Heat load usually means the cooling requirement in summer — solar gain through glazing, people and equipment. Air conditioning and air-to-air heat pumps need both; air-to-water heating systems only need the first.
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