Heat Pump for an Old House With Radiators: When It Makes Sense

Yes – a modern heat pump can heat an old house with radiators, even one that is only partially insulated. With an air-to-water heat pump, what matters is the temperature of the heating water, not the age of the building. If your system can heat the house with water at around 50–55 °C instead of the original 70 °C, the pump runs with a real-world seasonal coefficient of performance (SCOP) in the region of 2.5 to 4, and heating works out cheaper to run than gas or direct electric heating. But if the radiators need 70 °C even in freezing weather, efficiency drops and the payback period stretches out. In this article we honestly show when it makes sense, when it is better to insulate first or replace the radiators – and what to watch out for in the older housing stock around Šumperk and Zábřeh.

What matters is the heating water temperature, not the age of the house

A heat pump draws heat from the outdoor air and "pumps" it up into the heating water. A simple rule applies: the lower the water temperature it has to produce, the higher its efficiency. The catalogue SCOP of quality units ranges roughly between 3.3 and 4.5 (peaking around 5), but that applies to low-temperature operation. At higher system temperatures and with a poorer installation, it realistically drops to roughly 2.5 to 4.

Efficiency also falls as the outdoor temperature drops – the instantaneous coefficient of performance (COP) is typically around 4–5 at +7 °C, roughly 3–4 around 0 °C, and only 2–2.8 at −10 °C. The worst combination therefore occurs precisely when you need the most heat: in freezing weather and with the radiators set to a high temperature. That is why, with an older house, the first thing we look at is not the brand of the pump but what water temperature the house can actually be heated to.

To give you an idea: underfloor heating runs ideally at around 35 °C, whereas classic radiators in older houses were designed for a much higher flow temperature (originally around 70 °C or more). If you can run those same radiators at roughly 55 °C, the pump uses considerably less electricity than at 70 °C. Every degree of water temperature you save counts.

When a heat pump makes sense in an old house – and when to wait

From our experience in the Olomouc region, going for a heat pump pays off when most of these points apply:

• the house is at least partially insulated and has had its windows replaced,
• the radiators currently run fairly lukewarm and water up to around 55 °C is enough for them even in winter,
• the house's heat loss is reasonable for its size,
• you have (or will arrange) a distribution tariff for heating with a wide low-rate window.

Conversely, we recommend slowing down and dealing with the building envelope or the radiators first if:

• the house is uninsulated, its heat loss is high, and the radiators have to run at 70 °C in freezing weather,
• only some rooms have undersized radiators that force the whole system to "push" the temperature up,
• you are planning insulation or window replacement within the next one to two years.

Radiators: when the existing ones are enough and when to replace them

A lower water temperature means a radiator needs a larger surface area to deliver the same output to the room. The good news is that older houses are often "over-radiatored" – the cast-iron sections and the original panel radiators are oversized, and once balanced they handle a lower flow temperature without any trouble.

So you often do not need to replace radiators throughout the house. Usually it is enough to swap just the few weakest radiators in the rooms that would otherwise force the whole system to run at a higher temperature – typically for modern panel radiators with a higher output. Which ones those are only becomes clear from a room-by-room calculation, not from a rough guess. We always carry out this check before ordering the pump, so that both the output and the temperature are a good match.

High-temperature heat pumps and gas hybrids

When replacing the radiators is not an option – for example in heritage-listed houses or in a flat – there are two routes available:

• High-temperature heat pumps deliver a higher heating-water temperature and can drive even the original radiators. The trade-off is a lower SCOP (and therefore higher running costs) and a higher purchase price, so we deploy them specifically where there is no other option.
• Hybrid (bivalent) operation with your existing gas boiler – the pump covers most of the heating season in economy mode, and the boiler only steps in during the hardest frosts, when the pump would run inefficiently. That way you make use of the boiler you already have.

A hybrid makes the most sense in the foothill areas around Jeseník and Rýmařov, where frosts tend to be long and hard – the few coldest days of the year then do not push up your electricity consumption.

Insulate first, or go straight for a heat pump?

Let's be honest: on an uninsulated house, a heat pump is no miracle. High heat loss means a larger (and more expensive) unit, a higher water temperature, and a worse SCOP. If you are planning insulation or window replacement, ideally do it first – it reduces the heat demand and allows a smaller pump and a lower flow temperature. That significantly improves the payback.

If insulation is not currently on the cards, you do not have to rule out a heat pump entirely – the answer is usually a transitional hybrid with the boiler or a high-temperature unit. But we always tell the client where the limits are, and we never talk anyone into a solution that will not pay for itself.

How much it costs and what about subsidies in 2026

A complete air-to-water heat pump solution for a family house, including installation, controls and documentation, most often comes to between 200,000 and 350,000 CZK (up to 400,000 CZK for more demanding installations). The exact price depends on the output, the brand and the complexity of the installation.

In terms of running costs, the pump comes out favourably: at the low rate of the D57d tariff (around 4 CZK/kWh) and a SCOP of 3.5, 1 kWh of heat works out at about 1.1–1.2 CZK, whereas with gas it tends to be in the region of 1.6–3.2 CZK and with direct electric heating around 4 CZK. The D57d tariff offers 20 hours of the low rate per day, which covers almost all of your heating; we do, however, recommend checking the current price list with EG.D, the distributor that supplies the Šumperk region.

Watch out when it comes to subsidies – the Nová zelená úsporám programme (NZÚ, the Czech state energy-savings scheme) changed fundamentally in 2026. For ordinary households there is no longer a direct grant towards a heat pump, but an interest-free loan (0 %, with the interest covered by the state). A direct grant of up to 150,000 CZK towards an air-to-water heat pump is available only under the NZÚ Light programme for low-income and vulnerable households. Applications open on 25 June 2026, a renovation passport is mandatory, and the house must have been completed before 1 July 2013. We recommend verifying the binding conditions and amounts directly at novazelenausporam.cz.

If you have an older house with radiators around Šumperk, Zábřeh or Mohelnice and you are considering a heat pump, get in touch. As two specialists with more than ten years of experience, we first calculate the heat loss and the water temperature, and only then recommend a solution – or honestly tell you that it makes more sense to insulate first. A no-obligation consultation commits you to nothing.