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Heat pumps · UK

IGLOO MultiTherma 21 HD + ElectroBox

The IGLOO MultiTherma 21 HD + ElectroBox is an air-to-water heat pump with a SCOP of 4.45 (35 °C) and a sound power level of 56 dB(A). Under permitted development the limit is 37 dB(A) measured 1 m in front of the centre of a neighbour’s habitable-room door or window. Free-standing, the indicative minimum distance is 3.6 m; against a wall 5.0 m.1,2,3

Last updated: Technical specificationsRules in the UK⇄ Compare this model
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SCOP (35 °C)
4.453

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

Heating capacity (A7/W35)
6.29kW2
Official source
Outdoor unit sound power
56dB(A)3
Official source
Refrigerant
R2901
Official source
Type (source)
Air-to-water1
Official source
UK

Rules in the UK

Minimum distance to your neighbour

MCS 020(a) (England, permitted development since 29 May 2025)4 · 1 m in front of the centre of a neighbour’s habitable-room door or window

Permitted development (MCS 020(a))≤ 37 dB(A) · LAeq,5min
Free-standing3.6 m
Against wall5 m
In corner7.1 m

Indicative calculation (hemispherical, no barriers). Not a substitute for an MCS 020 assessment.

Boiler Upgrade Scheme

Check conditions

£7,500 – £9,0005Fixed grant (England & Wales)

Fixed grant in England and Wales, deducted from your installer’s quote. £9,000 when replacing oil or LPG off the gas grid (until March 2027). Scotland: Home Energy Scotland grant instead.6,7

  • Must be MCS-certified (product and installer). Check the Ofgem product eligibility list.
  • Rated output 8 kW; the scheme covers systems up to 45 kW.
Heat pump grants in the UK explained →

Technical specifications

General
Type (source)Air-to-water1
Compressors11
Capacity controldrehzahlregelung1
Performance
Heating capacity (A7/W35)6.29 kW2
Rated output 35 °C8 kW3
Rated output 55 °C8 kW3
Efficiency
SCOP (35 °C)4.453
Seasonal efficiency ηs 35 °C175 %3
Seasonal efficiency ηs 55 °C175 %3
Energy label 35 °CA+++3
Energy label 55 °CA++3
COP A7/W355.171
COP A2/W354.251
COP A-7/W353.421
Noise
Outdoor unit sound power56 dB(A)3
Refrigerant
RefrigerantR2901
Refrigerant GWP32
Refrigerant charge2.2 kg1
Electrical
Max. power input6.9 kW1
Connectivity & smart
SG ReadyYes1

How it ranks

SCOP (35 °C): better than 7% of comparable models in our database (Heat pumps · Air-to-water · 8–10 kW; n = 171).

Rank 158 of 172

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.

More from IGLOO

All IGLOO models (10) →

Guides on heat pumps

How we collect and check this data →

Frequently asked questions

Can I install the IGLOO MultiTherma 21 HD + ElectroBox without planning permission?

Under MCS 020(a) (England, permitted development since 29 May 2025) the unit must not exceed 37 dB(A) 1 m in front of the centre of a neighbour’s habitable-room door or window. With a sound power of 56 dB(A) that indicatively means 3.6 m free-standing, 5.0 m against a wall or 7.1 m in a corner. Your MCS installer must confirm this.1,2,3

How much Boiler Upgrade Scheme grant can you get for the IGLOO MultiTherma 21 HD + ElectroBox?

£7,500 in England and Wales, provided the product and installer are MCS-certified (£9,000 when replacing oil or LPG off the gas grid, until March 2027). The installer applies and deducts the grant from your quote.1,2,3

Which refrigerant does the IGLOO MultiTherma 21 HD + ElectroBox use?

The IGLOO MultiTherma 21 HD + ElectroBox uses R290.1,2,3

Sources

  1. List of eligible heat pumps (BEG) — Bundesamt für Wirtschaft und Ausfuhrkontrolle (BAFA) · accessed 27 Sept 2026
  2. Heat Pump Keymark certificates — EHPA / DIN CERTCO (Heat Pump KEYMARK) · accessed 29 Sept 2026
  3. European Product Registry for Energy Labelling (EPREL) – heat pumps — Europese Commissie · accessed 15 Oct 2026
  4. MCS 020(a) (England, permitted development since 29 May 2025)
  5. Boiler Upgrade Scheme: what you can get — GOV.UK · accessed 27 Sept 2026
  6. Boiler Upgrade Scheme: guidance for installers (V5) — Ofgem · accessed 27 Sept 2026
  7. Boiler Upgrade Scheme product eligibility — Ofgem · accessed 27 Sept 2026