Worcester Bosch is part of the Bosch group, and its Compress air source heat pumps cover three different needs: the quiet, high-temperature 5800i AW, the 3400i AWS split with its compact indoor unit, and the 7001i AW with outputs up to 17kW for larger homes.
Worcester Bosch’s quietest heat pump, Quiet Mark certified with sound power from 40dB(A). It uses natural R290 refrigerant, reaches flow temperatures up to 75°C and comes in 4kW, 5kW and 7kW sizes.
Monobloc
A split heat pump that links the outdoor unit to a compact wall-hung indoor unit with refrigerant pipes. It uses R32 refrigerant, reaches flow temperatures up to 60°C and comes in 4kW, 6kW, 8kW and 10kW sizes.
Split
A monobloc heat pump with the widest output range in the line-up, from 5kW to 17kW, for larger homes. It reaches flow temperatures up to 62°C, uses R410A refrigerant and is Quiet Mark certified.
Monobloc
Each Compress model suits a different kind of home. Here’s how the three compare on the details that matter most.
| Compress 5800i AW | Compress 3400i AWS | Compress 7001i AW | |
|---|---|---|---|
| Type | Monobloc | Split | Monobloc |
| Outputs | 4, 5 and 7kW | 4, 6, 8 and 10kW | 5, 7, 9, 13 and 17kW |
| Refrigerant | R290 (natural) | R32 | R410A |
| Max flow temperature | Up to 75°C | Up to 60°C | Up to 62°C |
| Noise | Quiet Mark, from 40dB(A) sound power | From 59dB(A) sound power | Quiet Mark, from 47dB(A) sound power |
| Warranty | 2 years standard, up to 7 years depending on your installer | 2 years standard, up to 7 years depending on your installer | 2 years standard, up to 7 years depending on your installer |
| Best for | Small to medium homes, and anywhere noise is a concern | Homes suited to a split system with a compact indoor unit | Larger homes that need more than 7kW |
Our comparison guides put each model side by side in plain English, so you can see the differences before you speak to an installer.
The Compress 5800i AW stands out. It's Quiet Mark certified, uses natural R290 refrigerant and reaches 75°C. Worcester Bosch reports that when The Times and Quiet Mark analysed over 850 heat pumps on the UK market, it was among the few that passed Quiet Mark's acoustic standards. As with any brand, a good design and installation matter just as much.
A Worcester Bosch heat pump is priced as part of a full installation, so there's no single figure. The Energy Saving Trust puts the typical cost of installing an air source heat pump at around £14,000. Your quote depends on which Compress model and size you need, your home, any radiator upgrades and the cylinder and controls. In England and Wales, the £7,500 Boiler Upgrade Scheme grant comes off the bill.
It's Worcester Bosch's quietest heat pump and is Quiet Mark certified. Worcester quotes a sound power from 40dB(A), and a sound pressure of 32dB(A) at one metre for the 4kW model and 34dB(A) for the 5kW and 7kW. It has an integrated diffuser to help keep fan noise down.
Once registered, every Worcester Bosch heat pump comes with a 2-year guarantee as standard. Longer guarantees, up to 7 years, are available depending on your installer's qualifications and loyalty scheme level, and involve an extra inspection check. Ask your installer which guarantee length they can offer before you go ahead.
With the Compress 5800i AW and 7001i AW, all the refrigerant stays in the outdoor unit and water pipes run into your home. The Compress 3400i AWS is a split, so refrigerant pipes link the outdoor unit to a compact wall-hung indoor unit. A split needs an installer qualified to work with refrigerant, while a monobloc's refrigerant circuit is sealed inside the outdoor unit.
If noise is your main concern and your home needs 7kW or less, the Compress 5800i AW is the stand-out choice. For bigger homes needing more output, the 7001i AW goes up to 17kW. The 3400i AWS suits homes where a split system with a compact indoor unit works best. A heat loss survey will confirm the right size.
You can, as long as the heat pump, the installation and your home meet the scheme rules, which your installer will check. In England and Wales, the Boiler Upgrade Scheme gives £7,500 towards an air source heat pump, or £9,000 if your off-gas-grid home is replacing oil or LPG, thanks to an extra £1,500 available until March 2027. Your installer applies on your behalf. In Scotland, Home Energy Scotland offers grant funding instead.
Often, yes. The Compress 5800i AW reaches flow temperatures up to 75°C, which Worcester Bosch says suits a wider range of UK homes. The 7001i AW reaches 62°C and the 3400i AWS 60°C. Heat pumps are most efficient at lower temperatures, so your installer may still recommend a few larger radiators after a heat loss survey.
Our recommended installers
These recommended installers in our network fit Worcester Bosch heat pumps. Each one designs the system around your home, from the heat loss survey to the final handover.
Tell us where you live and we’ll point you to our recommended installer for your area, who can survey your home and size the right model for you.
