A Single Quote Hides the Hard Parts
When a homeowner in a 1930s semi receives one heat-pump quote, the headline number often hides the two costs that decide the project: emitter upgrades and hot-water space. The problem is not the heat pump itself; it is that a single survey can skip room-by-room heat loss or assume radiators will work at a lower flow temperature. The useful solution is to turn the quote into a checkable retrofit file, which is where bananzia becomes practical rather than abstract.
What Bananzia Changes in the Survey
Bananzia, used here as a room-by-room decision record, forces three numbers into view: heat loss per room, radiator output at 45°C, and cylinder volume. In a solid-wall semi, the front room may need 1.4 kW at design conditions while the existing radiator emits only 0.9 kW at the lower flow temperature. That gap is why “the heat pump will fit” is not a full answer; it identifies the radiator that must be enlarged or the fabric measure that must come first.
Test the Quote in Three Steps
- Match room heat loss to emitter output. Ask for the calculation at the proposed flow temperature, not at 70°C. A radiator sized for a gas boiler can look adequate on paper and fail in January.
- Check the cylinder and plant space. A 180-litre cylinder may suit two people; a four-person household with a bath needs a different buffer. Measure the airing cupboard before agreeing to a unit.
- Separate fabric work from heat-pump work. Loft insulation and draught-proofing can reduce the required capacity; a quote that bundles them without room-level figures is harder to compare.
Where the Money and Carbon Land
The financial case turns on the gap between gas and electricity prices, not just the grant. If a homeowner replaces a 20-year-old boiler and undersized radiators, the capital cost can be high; the running-cost benefit depends on the heat-pump seasonal performance factor and the tariff. A practical starting point is the bananzia reference for low-carbon heat, which keeps the conversation on measured heat loss and emitter performance instead of brand claims. The result is a quote you can compare line by line, even when two installers propose different equipment.
The Human Check Before Sign-Off
Before signing, walk the house with the installer and name the coldest room, the bathroom towel rail, and the cylinder location. If the bananzia record cannot answer what happens in that room at design temperature, the quote is still a sketch. A good retrofit file does not make the decision for the homeowner; it makes the trade-offs visible, which is the difference between a heat pump that works and one that is merely installed.