2026 heat-pump efficiency in heat emitters: radiators vs underfloor heating

Radiators vs underfloor heating: what changes in the numbers

For buyers comparing radiator retrofits with underfloor heating in 2026, the catalog evidence points to a simple hierarchy: lower flow temperatures usually make it easier to realise high seasonal efficiency, but emitter choice is not the only variable that determines whether a heat pump is financially convincing.

The broad EPREL-linked market snapshot shows that average declared SCOP differs materially by heat-pump type: air-water units average 4.54 across 30,452 models (type_efficiency / EPREL Public API · type aggregation), ground-water units average 4.77 across 213 models (type_efficiency / EPREL Public API · type aggregation), and water-water units average 6.15 across 31 models (type_efficiency / EPREL Public API · type aggregation). The absolute spread from air-water to water-water is 1.61 SCOP points (type_efficiency / EPREL Public API · type aggregation).

That matters because underfloor heating is the emitter most naturally aligned with the lower flow temperatures at which high SCOP declarations are typically achievable. The registry used here does not record emitter type per model, so it cannot directly say “this unit with radiators” versus “the same unit with underfloor heating”. What it does show is the efficiency range available in the market, and that range is clearly wider than the difference between many national price environments.

So the practical reading is this: underfloor systems give the cleanest route to high seasonal performance, but a radiator retrofit can still make sense where tariff conditions are favourable, subsidy support is strong, or the existing radiator circuit can run at lower temperatures after emitter upsizing, balancing or insulation work. Buyers can benchmark current catalog performance in the live EPREL catalog, compare national conditions in the 32-country dashboard, and check definitions such as SCOP in the HVAC glossary.

Where the efficiency gap comes from: SCOP, capacity and noise by heat-pump type

The market is dominated by air-water products, not by niche high-efficiency source types. Air-water accounts for 30,452 listed models, versus 213 ground-water and just 31 water-water models (type_efficiency / EPREL Public API · type aggregation). That means the highest-efficiency source categories are real, but small in product-count terms.

Average declared capacity also differs sharply. Water-water units average 35.65 kW (type_efficiency / EPREL Public API · type aggregation), ground-water 18.45 kW (type_efficiency / EPREL Public API · type aggregation), and air-water 11.83 kW (type_efficiency / EPREL Public API · type aggregation). So the higher-SCOP source types are not smaller boutique machines; on average they are larger units. The capacity spread from air-water to water-water is 23.82 kW (type_efficiency / EPREL Public API · type aggregation).

Outdoor noise follows the same pattern. Average outdoor sound power is 59.8 dB for air-water (type_efficiency / EPREL Public API · type aggregation), 58.8 dB for ground-water (type_efficiency / EPREL Public API · type aggregation), and 42.0 dB for water-water (type_efficiency / EPREL Public API · type aggregation). The difference between air-water and water-water is 17.8 dB (type_efficiency / EPREL Public API · type aggregation). That is a large catalog gap, but again it reflects heat-pump type, not emitter type. The registry does not show that underfloor heating itself makes a unit quieter.

For radiator-versus-floor decisions, the implication is narrower than many sales claims suggest. Emitter choice correlates with achievable system temperature, and system temperature affects delivered efficiency. But the catalog numbers here show no direct emitter/noise link, only source-type differences. Readers wanting a product-level sense of current acoustic performance can cross-check the quietest heat-pump leaderboard and the filtered air-water catalog.

How big the real-world performance spread is in today’s EPREL-linked market

At the top end of the current market, declared SCOP reaches 7.0 for Risch Kälte- und Klimatechnik GmbH OH I 4esr TWW W/W (top_models / EPREL Public API via Househeating Pulse catalog). The next entries are tightly clustered: Hoval Aktiengesellschaft 42 -Thermalia® twin (26) GW at 6.97 (top_models / EPREL Public API via Househeating Pulse catalog), Waterkotte GmbH CTC EcoTouch 525 (water/water) at 6.97 (top_models / EPREL Public API via Househeating Pulse catalog), Waterkotte GmbH EcoTouch DS 5034.5 T (water/water) at 6.97 (top_models / EPREL Public API via Househeating Pulse catalog), Master Therm tepelná čerpadla s.r.o. AQ30I-0WW at 6.97 (top_models / EPREL Public API via Househeating Pulse catalog), and ProCalor B.V. ProGH10-32DC at 6.95 (top_models / EPREL Public API via Househeating Pulse catalog).

Across the top 15 models, SCOP ranges from 6.88 to 7.0 (top_models / EPREL Public API via Househeating Pulse catalog). All 15 carry heating class APPP (top_models / EPREL Public API via Househeating Pulse catalog), which readers can compare against the broader APPP-class catalog filter and the current top SCOP leaderboard.

What does this say about radiator retrofits? Two things.

First, the best declared efficiencies are already available in the current market and are not confined to a single manufacturer. Second, the top-15 list includes multiple units with minimum declared capacity at 8.0 kW, 10.0 kW and 13.0 kW, alongside much larger 34.0 kW, 35.0 kW, 45.0 kW and 46.0 kW machines (top_models / EPREL Public API via Househeating Pulse catalog). So very high SCOP is not limited to one capacity band.

But the corpus cannot answer a stricter radiator question: how many of these top performers meet a specific radiator flow-temperature requirement. EPREL data in this snapshot does not provide the emitter-side hydraulic design details needed to prove “radiator-ready” performance case by case. For that, buyers need model datasheets and heat-loss calculations, ideally alongside the sizing calculator and the platform’s methodology notes.

When running costs favour heat pumps: the tariff-ratio break-even by country

Using the editorial threshold supplied here, a heat pump with SCOP 4 breaks even with gas when the electricity-to-gas tariff ratio is about 3.7. The cross-country snapshot shows that all 25 countries with both electricity and gas tariffs recorded are below 3.7 (country_compare / Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register). None of the recorded gas-and-electricity markets sits above that line (country_compare / Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register).

A few examples make the point:

Belgium, at 3.90 (country_compare / Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register), is the only listed market above the 3.7 threshold. France, at 1.78 (country_compare / Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register), and the Netherlands, at 1.49 (country_compare / Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register), are far below it. That means the operating-cost penalty for a radiator system that runs at a somewhat lower SCOP is much easier to absorb in some countries than in others.

Retrofit vs new build: what the country data means for radiator upgrades and low-temperature floors

New build still has the cleaner thermodynamic case. Underfloor heating is designed around low flow temperatures, which is the most reliable route to extracting the higher SCOP levels visible in the ground-source leaderboard and the air-water top-SCOP ranking.

Retrofit is more conditional. Germany is a good example. Household electricity stands at 0.3869 €/kWh and gas at 0.1223 €/kWh (country_profile DE / Eurostat tariffs (band DC/D2 latest); NASA POWER 30y normal; EEA grid CO₂; subsidies captured manually from official programme pages). That ratio of 3.16 still sits under the 3.7 break-even marker, but it leaves less margin for a poor radiator design than France’s 1.78 ratio (country_compare / Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register). Germany also offers up to 21,000 € under BEG EM, with support capped at 70% of cost and bonuses for natural refrigerant or ground/water source, early fossil replacement, and low income (country_profile DE / Eurostat tariffs (band DC/D2 latest); NASA POWER 30y normal; EEA grid CO₂; subsidies captured manually from official programme pages). Those subsidy mechanics can make emitter upgrades more rational even where running-cost margins are tighter; see the German subsidy page and the subsidy calculator.

France is different. Electricity is 0.2561 €/kWh, gas 0.1436 €/kWh, and grid CO₂ just 56.0 g/kWh (country_profile FR / Eurostat tariffs (band DC/D2 latest); NASA POWER 30y normal; EEA grid CO₂; subsidies captured manually from official programme pages). MaPrimeRénov' reaches 11,000 € for geothermal in the Bleu band and 5,000 € for air-water, while air-air is excluded (country_profile FR / Eurostat tariffs (band DC/D2 latest); NASA POWER 30y normal; EEA grid CO₂; subsidies captured manually from official programme pages). In that setting, even a radiator retrofit has a relatively forgiving operating-cost backdrop, while low-temperature floors and geothermal get extra policy support; see France’s country profile and French subsidies.

Germany’s tariff history also shows why the argument has become more sensitive. Household electricity rose from 0.2987 €/kWh in the first half of 2018 to 0.3869 €/kWh in the second half of 2025, an increase of 0.0882 €/kWh (tariff_history / Eurostat · electricity household band · series for DE). The series peaked at 0.4125 €/kWh in the first half of 2023 (tariff_history / Eurostat · electricity household band · series for DE) before easing. The corpus does not include German gas history, so it cannot quantify whether the full electricity-gas gap widened or narrowed over the same period.

What buyers should infer from the market leaders: the models already proving the point

The strongest lesson from the leaderboard is not that every home needs underfloor heating. It is that the market already contains products with declared SCOP near 7.0, and that those products span multiple manufacturers and capacities rather than a single exotic corner of the catalog (top_models / EPREL Public API via Househeating Pulse catalog).

That supports three practical inferences.

First, underfloor heating remains the easiest route to exploit those headline SCOP levels, because the emitter side can usually run cooler. Second, radiator retrofits are more credible where the local electricity-to-gas ratio is comfortably below 3.7, as in France at 1.78 and the Netherlands at 1.49 (country_compare / Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register). Third, buyers should treat source type and national economics as at least as important as emitter type alone.

For a shortlist, start with the top SCOP overall leaderboard, then inspect individual model pages such as Risch Kälte- und Klimatechnik GmbH OH I 4esr TWW W/W, Hoval Aktiengesellschaft 42 -Thermalia® twin (26) GW, and Waterkotte GmbH CTC EcoTouch 525 (water/water). The underlying registry is EPREL, while tariff statistics in this article come from Eurostat. For payback questions, the right next step is not another generic average but a project-specific run through the heat-pump payback calculator.

Sources

• EPREL Public API · type aggregation — snapshot as of 2026-05-22
• EPREL Public API via Househeating Pulse catalog — snapshot as of 2026-05-22
• Eurostat · NASA POWER · EEA · Househeating Pulse subsidy register — snapshot as of 2026-05-22
• Eurostat tariffs (band DC/D2 latest); NASA POWER 30y normal; EEA grid CO₂; subsidies captured manually from official programme pages — Germany profile, snapshot as of 2026-05-22
• Eurostat tariffs (band DC/D2 latest); NASA POWER 30y normal; EEA grid CO₂; subsidies captured manually from official programme pages — France profile, snapshot as of 2026-05-22
• Eurostat · electricity household band · series for DE — snapshot as of 2026-05-22

Continue reading

• Heat pump sizing guide — How to match output in kW to building heat loss before comparing SCOP tables
• Heat pump subsidy guide — A practical route through national grants, caps and eligibility rules
• Heat pump noise guide — What catalog dB figures can and cannot tell buyers before installation
• Radiator retrofit guide — When existing emitters can stay, and when low-temperature upgrades matter most