A heat loss survey is a room-by-room assessment that calculates how much heat your home loses on a cold day, which tells you what size of heat pump you need and whether your radiators can deliver enough warmth. It follows the MCS method, the standard used for heat pump design across the UK, and it is the foundation for every other decision in your quote.
Homeowners in Gwynedd thinking about insulation work can use the survey to see how it would change their heat pump size. For Gwynedd homes with extensions or loft conversions, each part of the house is assessed on its own construction. The survey in Gwynedd includes a check of where the outdoor unit could sit and how its sound would reach neighbours.
Who it suits
- Self-builders and architects who need emitter and system sizes early
- Anyone getting a heat pump quote, as the first step
- Landlords comparing properties before deciding where to switch first
- Homes with an existing heat pump that seems undersized or expensive to run
Grants and rules for heat pumps in Wales
In Wales the Boiler Upgrade Scheme gives £7,500 towards an air source heat pump (£9,000 if it replaces oil or LPG, from 21 July 2026 to 31 March 2027; £2,500 for air-to-air). The MCS-certified installer named in your quote applies to Ofgem for you, and the grant comes off your quote.
There is no VAT on installing a heat pump anywhere in the UK, Wales included, until 31 March 2027. Planning rules for heat pumps in Wales are set by the Welsh Government and differ from England's, so the surveyor checks the unit position against them.
Heat loss survey prices in Gwynedd
These are guide prices for Gwynedd, installed and including VAT. Your final price is fixed in a written quote after the survey and depends on the heat loss of the house, the radiators that need changing and where the unit goes.
| Survey | Guide price |
|---|---|
| Home survey and heat loss calculation with an installation quote | Free |
| Stand-alone heat loss survey and report | £150–£400 |
Inc VAT. A stand-alone report is for homeowners who want the design without an installation quote.
Towns we cover in Gwynedd
We cover 9 towns in Gwynedd for heat loss surveys. Each links to local guide prices and the grant position for Wales.
| Town | Postcode district | Nearest town | Midwinter daylight |
|---|---|---|---|
| Bangor (Gwynedd) | LL59 | Beaumaris | 7 h 31 min |
| Bala | LL23 | Dolgellau | 7 h 35 min |
| Beaumaris | LL58 | Bangor (Gwynedd) | 7 h 31 min |
| Caernarfon | LL55 | Llangefni | 7 h 32 min |
| Dolgellau | LL40 | Machynlleth | 7 h 36 min |
| Holyhead | LL65 | Llangefni | 7 h 30 min |
| Llangefni | LL77 | Bangor (Gwynedd) | 7 h 31 min |
| Porthmadog | LL49 | Pwllheli | 7 h 34 min |
| Pwllheli | LL53 | Porthmadog | 7 h 35 min |
Heat loss surveys questions
Will the survey check noise from the outdoor unit?
Yes. The surveyor identifies possible positions for the outdoor unit and carries out the MCS noise assessment, which estimates the sound level at the nearest neighbouring window from the unit's sound power level, distance and any barriers. In England, meeting the MCS planning standards is one of the conditions for permitted development. Wales, Scotland and Northern Ireland have their own rules, which we check.
How long does a heat loss survey take?
A typical survey takes 1–3 hours on site, depending on the size and complexity of the home. Larger or older houses with mixed construction, extensions or many rooms take longer. The calculations and design are completed afterwards, and the results are included in your quote or stand-alone report.
Can I use the heat loss report to get other quotes?
Yes. A stand-alone heat loss report is yours to use, including sharing it with other installers so their quotes are based on the same figures. Comparing quotes like for like makes it easier to see differences in equipment, radiator upgrades and workmanship terms. The report states the assumptions used wherever construction could not be confirmed.
What is a design flow temperature?
The design flow temperature is the temperature of the water sent to your radiators or underfloor heating on the coldest design day. Heat pumps are more efficient at lower flow temperatures, typically around 35–50°C. Choosing it is a balance: a lower figure improves efficiency but can mean larger radiators in some rooms, so the design shows both.