The heat pump questions advisers can put to a retrofit client

Green refurbishment lending means a heat pump now appears in more of the renovation plans that reach an adviser's desk. Two houses can arrive with similar quotes and need very different amounts of work, and the gap only shows once someone has measured the building. Three questions let an adviser test a quote without any heating knowledge.

1. Has anyone measured the house?

A heat pump should be sized from a room-by-room heat loss calculation. The installer measures each room, records the walls, windows, floors and insulation, and works out how much heat that room loses on a cold day. The total sets the size of the unit, and the room figures show which radiators can stay and which need replacing.

Two detached houses we worked on in Newton Abbot show what that means for a budget. The first needed new pipework throughout and 14 new radiators, and some of its rooms had no radiator at all before we started. The second needed one radiator replaced.

If your client holds a quote with no heat loss survey behind it, the radiator and pipework lines are an estimate, and those are the lines that move once work starts. Ask whether a survey has been done and who carried it out. A quote built on one will name a design flow temperature and list the radiators room by room. Those two lines explain most of the difference in heat pump installation costs in the South West and elsewhere, far more than the brand of heat pump on the quote.

2. Who handles the grant, and when does it come off?

In England and Wales the Boiler Upgrade Scheme pays £7,500 towards an air source heat pump. Until March 2027, homes heated by oil or LPG with no mains gas connection can get an extra £1,500. One grant is available per property.

The MCS-certified installer applies for the grant and deducts it from the quote. Your client pays the net price and never waits for a refund. For borrowing, that matters in two ways. The sum to fund is the net figure after the grant, and only an MCS-certified installer can claim it, so a client who hires a cheaper uncertified contractor loses the grant along with the paperwork. Check that the quote shows the grant as a deduction and gives the installer's MCS certification number. For clients who want the eligibility detail first, I keep a plain-English explainer on how the Boiler Upgrade Scheme works.

3. What should the client hold at the end?

There are three. The MCS certificate comes first, because a buyer's conveyancer or a future lender will ask for it. The design paperwork comes second: the heat loss calculation, the radiator schedule and the design flow temperature. The third is a manufacturer's warranty registered at commissioning, which the installer should complete and hand over before leaving.

The design paperwork is the document clients tend to lose. When I audit another installer's job as an assessor, I check the system against what it was designed to do. If those figures were never written down, nobody can tell whether a poor result came from the design, the installation or the way the house is run, and that includes whoever services the system in five years.

A note on sequencing

A heat loss survey takes one visit, and the installation on a typical house takes about a week. Where the heat pump sits inside a wider refurbishment, ask the installer where it falls in the programme. New pipework laid before the plastering and flooring go down costs less than pipework chased into finished walls, and a bridging term set before anyone has checked that order can run short.