Homeowner Received Two Heat Pump Quotes – But Which Design Was Actually Better?

Homeowner Received Two Heat Pump Quotes – But Which Design Was Actually Better?

A homeowner contacted us after receiving two heat pump quotations from different installation companies. The prices were almost identical. The problem was that the proposed system designs were completely different. Both companies seemed professional, both had good reviews, and both were confident their design was correct. The homeowner felt stuck. Rather than simply choosing the cheaper quote or tossing a coin between two plausible-sounding proposals, they wanted to understand which design would actually provide the best comfort and long-term performance.

The Property

The property was built around 2010 and was being heated by a gas boiler. Downstairs was heated using underfloor heating divided into multiple zones. Upstairs used conventional radiators. One of the installers had already completed a heat loss calculation, which the homeowner sent to us for review. We also arranged a video call so we could understand how the property was actually used day to day.

The Two Designs

The first installer proposed retaining all five underfloor heating zones downstairs, keeping the existing upstairs thermostat, and installing a buffer tank with an additional circulation pump. The second installer proposed removing four of the five downstairs thermostats, operating the entire downstairs area as a single zone, retaining one upstairs thermostat, and installing the system without a buffer tank using a direct configuration instead.

Both designs could potentially work. The question was which approach would provide the best balance of comfort, reliability, and efficiency for this specific property and the way the family used it. Neither proposal was obviously wrong on the surface, which made the decision genuinely difficult without a deeper review.

The Detail That Changed Everything

During our video call, we noticed something important that neither installer had raised in their proposals. The main kitchen and living area was south facing and featured large bifold doors. Even during relatively mild weather, solar gain through that glazing would significantly increase temperatures within the space at certain times of day.

This immediately raised concerns about thermostat positioning and zoning strategy. If a single thermostat was located within the kitchen and living area, the rest of the downstairs could become underheated. The thermostat would become satisfied early due to the solar gain and shut the system down before other rooms had reached temperature. However, if the thermostat was positioned elsewhere downstairs to avoid this problem, the kitchen and living area could easily become too warm before the thermostat called for the heating to stop.

At that point it became clear that comfort needed to be considered just as carefully as efficiency, and that the zoning approach had to account for how the property actually behaved in practice rather than simply what looked tidiest on a design drawing.

Our Recommendation

After reviewing the property, discussing how the family used the space, and examining both proposals in detail, we felt a hybrid approach would provide the best result. We recommended two underfloor heating zones downstairs rather than five or one, one heating zone upstairs, and a buffer tank arrangement. The two downstairs zones would provide enough control to manage the solar gain from the bifold doors without creating the problems associated with excessive micro-zoning, which can restrict system flow rates and affect heat pump performance. Our article on what happens if too many TRVs are turned off explains why over-controlling a heat pump system through excessive zoning or valve closures can cause real problems, and why finding the right balance between comfort control and healthy flow rates matters more than simply maximising the number of zones.

The buffer tank was also an important part of the recommendation. On a system like this one, where underfloor heating actuators would progressively close as rooms reached temperature, a buffer tank helps maintain adequate water volume in the circuit and prevents the heat pump from cycling too frequently. Our article on do I need a volumiser with my heat pump explains in more detail how system water volume affects heat pump operation and when a buffer tank or volumiser is the right solution.

What Happened Next

We discussed the proposals in detail with the homeowner and helped draft an email outlining their concerns and questions for both installers. The responses were revealing.

The installer who had originally proposed retaining all five zones immediately dismissed the concern about solar gain and thermostat positioning and offered little technical explanation for their position. The second installer responded very differently. They acknowledged the concern, agreed that the point had merit, and admitted they had not considered it during the original design. They then repriced the system to include the buffer tank and the additional equipment required to support the revised zoning approach. The revised quotation increased by approximately £500, which was entirely reasonable given the additional components being supplied and the improved design that resulted.

The Outcome

At that point the homeowner felt they had their answer. The difference was not really the £500. The difference was how the two companies responded when a genuine design question was raised. One dismissed the concern without engaging with it. The other listened, reviewed the design, and adapted their proposal accordingly. The homeowner proceeded with the revised quotation and was extremely happy with their decision.

What This Case Study Shows

Choosing a heat pump installer is not just about price. When two quotes come in at almost identical figures, the design quality and the willingness to engage with detailed technical questions often matter far more than the final number on the page.

This case study also illustrates that a heat loss calculation alone does not guarantee a well-designed system. The calculation confirmed the heat pump was appropriately sized for the property. What it did not capture was how the property would actually behave during use, and how the specific layout and solar characteristics of the main living space needed to inform the controls and zoning strategy. Our article on 7 signs your heat pump may not be installed correctly covers the kinds of problems that arise when these details are not considered at the design stage, and what they tend to look like once the system is running.

If you have received multiple quotations and are not sure which design is best for your property, we can provide an independent review before you commit to an installation. We will assess the heat loss calculations, controls strategy, zoning arrangements, and overall system design and give you an honest view of which approach is most likely to deliver reliable comfort and efficient performance. You can find out more at ukheatpumphelp.co.uk/pre-installation-design-heat-loss-review.