Heatopia

So, if you’ve decided to go down the heat pump route, what are the key considerations?

Firstly, the most crucial factor influencing your decision is the heat pump’s design, a complex topic with many aspects to consider. When you engage an installer, their first priority will be to assess the heat loss of your property. In simple terms, heat loss refers to the amount of heat that escapes through your property’s walls, doors, windows, floors, and roof. This process is complex and could fill a series of blog posts in itself. For now, though, the installer will calculate the heat loss of your property using a standard outside temperature set for your location by MCS (the Microgeneration Certification Scheme), designed to heat your home to 21 degrees Celsius. This target temperature may vary slightly based on the type of room, so the installer will calculate heat loss for each room individually, then total it for the entire property.

Once this heat loss is established, you’ll need a heat pump that can at least match this output. Note that this figure refers to the heat output rather than electricity consumption, as heat pumps typically produce more heat than the energy they consume—often achieving efficiencies of 300% or more, depending on their coefficient of performance (COP). The COP value is key to understanding your running costs, so it’s definitely worth a deeper dive in a future post. There are also some excellent YouTube videos on this topic; if you haven’t yet, check out *Heat Geek* or *Urban Plumbers* for more insights.

Pay careful attention to any assumptions your installer makes when calculating heat loss, as even small mistakes can skew the result, leading to an oversized or undersized heat pump. For example, one installer we received a quote from had overestimated our heat loss because they assumed our house was built around 1982, resulting in a much higher estimate of around 80 W/m²—similar to a Victorian property. However, our home was actually built after 2010 and includes double glazing, good loft insulation, cavity wall insulation, and underfloor insulation. *Heat Geek* suggests a heat loss of around 20–40 W/m² for similar properties, meaning this installer had essentially doubled our heat loss and recommended a substantial 14 kW heat pump. This could have led to both higher initial and running costs, as an oversized heat pump would cycle on and off excessively, reducing the COP and driving up operating expenses. Be sure to review every detail of the design your installer provides, and don’t hesitate to ask questions to ensure you’re comfortable with their approach.

Unlike a gas boiler, a heat pump circulates hot water at a much lower temperature through your heat emitters (radiators or underfloor heating). As a result, you may need to upgrade your radiators to achieve sufficient heat output, as a lower flow temperature means you’ll require larger surface areas for heat emission. In our case, all the radiator sizing was incorrect, as the installer had based their calculations on an inflated heat loss for each room due to incorrect assumptions.

More on heat pumps design in the next blog post. Till then, keep warm but heat smart!