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Heat pumps · MT

CTA AH CL 21a

The CTA AH CL 21a is an air-to-water heat pump with a SCOP of 4.67 (35 °C) and a sound power level of 53 dB(A).1,2

Last updated: Technical specificationsRules in Malta⇄ Compare this model
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SCOP (35 °C)
4.672

Seasonal efficiency: how much heat you get per kWh of electricity across a heating season.

Outdoor unit sound power
53dB(A)2
Official source
Refrigerant
R2901
Official source
Type (source)
Air-to-water1
Official source
Rated output 35 °C
21kW2
Official source
MT

Rules in Malta

Water Heater Scheme (heat pump water heaters)

Unknown

REWS runs a national grant scheme for energy-efficient water heaters in homes; heat pump water heaters are eligible (alongside solar water heaters). The scheme has been extended to 31 December 2026, and part A of the application must be submitted before you buy and install the equipment. Grant amounts: see the REWS page (not verified by us).

Technical specifications

General
Type (source)Air-to-water1
Compressors11
Capacity controldrehzahlregelung1
Performance
Rated output 35 °C21 kW2
Rated output 55 °C21 kW2
Efficiency
SCOP (35 °C)4.672
SCOP (55 °C)3.832
Seasonal efficiency ηs 35 °C184 %2
Seasonal efficiency ηs 55 °C150 %2
Energy label 35 °CA+++2
Energy label 55 °CA+++2
COP A7/W355.311
COP A2/W354.321
COP A-7/W352.951
Noise
Outdoor unit sound power53 dB(A)2
Indoor unit sound power40 dB(A)2
Refrigerant
RefrigerantR2901
Refrigerant charge2.3 kg1
Electrical
Max. power input11.5 kW1
Connectivity & smart
SG ReadyYes1

How it ranks

SCOP (35 °C): better than 39% of comparable models in our database (Heat pumps · Air-to-water · ≥ 14 kW; n = 208).

Rank 126 of 209

Compared with every model on VersusIndex in the same group with a known value; equal values do not count as better. This says nothing about price, installation or reliability.

Similar models

Other brands, same type and a comparable size.

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Frequently asked questions

Which refrigerant does the CTA AH CL 21a use?

The CTA AH CL 21a uses R290.1,2

Sources

  1. List of eligible heat pumps (BEG) — Bundesamt für Wirtschaft und Ausfuhrkontrolle (BAFA) · accessed 27 Sept 2026
  2. European Product Registry for Energy Labelling (EPREL) – heat pumps — Europese Commissie · accessed 15 Oct 2026
  3. Water Heater Scheme (heat pump water heaters) — Regulator for Energy and Water Services (REWS)