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Heat pumps · UK

ViessmannIDU-A Hybrid HWMIW.A1.19-V054 / ODU 250-A AWMOF-251.A1.10-400-V002

The Viessmann IDU-A Hybrid HWMIW.A1.19-V054 / ODU 250-A AWMOF-251.A1.10-400-V002 is an air-to-water heat pump with a SCOP of 5.27 (35 °C) and a sound power level of 49 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 1.6 m; against a wall 2.2 m.1

Last updated: Technical specifications Rules in the UK ⇄ Compare this model
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SCOP (35 °C)
5.271

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

Heating capacity (A7/W35)
7.35kW1
Official source
Outdoor unit sound power
49dB(A)1
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)2 · 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-standing 1.6 m
Against wall 2.2 m
In corner 3.2 m

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

Boiler Upgrade Scheme

Check conditions

£7,500 – £9,0003Fixed 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.4,5

  • Must be MCS-certified (product and installer). Check the Ofgem product eligibility list.
  • Rated output 9.8 kW; the scheme covers systems up to 45 kW.
  • SCOP at 55 °C: 4.18. The installed system needs a SCOP of at least 2.8 (MCS calculation).
Heat pump grants in the UK explained →

Technical specifications

General
Type (source) Air-to-water1
System Hybrid (with gas boiler)1
Performance
Heating capacity (A7/W35) 7.35 kW1
Rated output 35 °C 9.8 kW1
Rated output 55 °C 9.37 kW1
Min. outdoor temperature -20 °C1
Efficiency
SCOP (35 °C) 5.271
SCOP (55 °C) 4.181
Seasonal efficiency ηs 35 °C 208 %1
Seasonal efficiency ηs 55 °C 164 %1
Energy label 35 °C A, , , 1
Energy label 55 °C A, , , 1
COP A7/W35 5.51
Noise
Outdoor unit sound power 49 dB(A)1
Indoor unit sound power 40 dB(A)1
Refrigerant
Refrigerant R2901
Refrigerant GWP 31
Refrigerant charge 2 kg1

Manufacturer documentation

External links to Viessmann's official website. The manufacturer may change or move documents; where they differ, the manufacturer's latest version applies.

Frequently asked questions

Can I install the Viessmann IDU-A Hybrid HWMIW.A1.19-V054 / ODU 250-A AWMOF-251.A1.10-400-V002 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 49 dB(A) that indicatively means 1.6 m free-standing, 2.2 m against a wall or 3.2 m in a corner. Your MCS installer must confirm this.1

How much Boiler Upgrade Scheme grant can you get for the Viessmann IDU-A Hybrid HWMIW.A1.19-V054 / ODU 250-A AWMOF-251.A1.10-400-V002?

£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

Which refrigerant does the Viessmann IDU-A Hybrid HWMIW.A1.19-V054 / ODU 250-A AWMOF-251.A1.10-400-V002 use?

The Viessmann IDU-A Hybrid HWMIW.A1.19-V054 / ODU 250-A AWMOF-251.A1.10-400-V002 uses R290.1

Sources

  1. Heat Pump Keymark certificates — EHPA / DIN CERTCO (Heat Pump KEYMARK) · accessed 29 Sept 2026
  2. MCS 020(a) (England, permitted development since 29 May 2025)
  3. Boiler Upgrade Scheme: what you can get — GOV.UK · accessed 27 Sept 2026
  4. Boiler Upgrade Scheme: guidance for installers (V5) — Ofgem · accessed 27 Sept 2026
  5. Boiler Upgrade Scheme product eligibility — Ofgem · accessed 27 Sept 2026