Worcester Bosch 7001i vs Mitsubishi Ecodan (UK 2026)

Worcester Bosch 7001i and Mitsubishi Ecodan represent two different routes into the UK premium heat pump market - Worcester via brand trust built across two decades of gas boilers, Mitsubishi via purpose-built heat-pump engineering since 2009. Both are MCS-certified and both qualify for the £7,500 Boiler Upgrade Scheme grant. The differences come down to efficiency, noise, installer skill base, and the question of whether you want the hybrid-with-gas-backup option.

Worcester Bosch Compress 7001i AW: SCOP 3.8-4.1 across the 4-17kW range (per Worcester Bosch data sheets). The 8kW model commonly fitted in UK 3-bed semis returns SCOP ~3.95 at 35°C flow. A++ Energy Label rating overall but at the lower end of the A++ band.

Mitsubishi Ecodan PUZ-WM: SCOP 4.0-4.4 across the 5-14kW range. The 8.5kW model returns SCOP 4.2 at 35°C - an ~6-8% efficiency advantage over the 7001i at equivalent capacity. A++ Energy Label rating across the range.

At typical UK electricity prices of £0.27/kWh and a 12,000 kWh annual heating demand, the SCOP gap translates to roughly £150-£250 per year of running cost difference at moderate use - meaningful over a 15-year ownership period but not a deciding factor by itself. The Ecodan's noise advantage is typically the more practical tipping point.

Worcester Bosch's distinctive offer in this comparison is the hybrid configuration - the 7001i can be installed alongside a working Worcester Greenstar gas boiler as a bivalent system. The heat pump handles the bulk of the heating load at moderate outdoor temperatures (above ~3°C); the gas boiler kicks in for peak winter cold spells when the heat pump's efficiency drops.

The argument for hybrid: if you have a working Worcester gas boiler with several years of life left, hybrid means you don't decommission a functional appliance. The heat pump can be smaller (4-6kW instead of 8-10kW) and cheaper to install. Annual gas usage drops to 20-30% of pre-install baseline.

The argument against: the BUS grant applies to full-replacement installs only - the grant rules require the heat pump to be the primary heating system, which excludes most bivalent configurations. Without the grant, the £7,500 saving disappears and the hybrid economics get much harder to justify. Additionally, the UK heat-pump market is moving toward full electrification by 2030 - investing in gas infrastructure in 2026 may have shorter useful life than a full heat pump install.

The Ecodan has no hybrid option - it's full-replacement only. For most UK retrofits in 2026, the BUS grant tips this decisively toward full replacement, which makes the Ecodan's lack of hybrid option a non-issue.

The 8-10 dB(A) noise gap between the 7001i and the Ecodan at 1m is large enough to be the deciding spec for many installs. The numbers from the MCS product list:

Worcester Bosch 7001i 8kW: 51 dB(A) at 1m, sound power 63 dB(A). The 12kW variant is 53 dB(A) at 1m.

Mitsubishi Ecodan PUZ-WM85 (8.5kW): 44 dB(A) at 1m, sound power 56 dB(A). The 11.2kW variant is 46 dB(A) at 1m.

The MCS permitted-development planning rules cap noise at 42 dB(A) at 1m from the nearest neighbouring property. The 7001i typically needs 4-5m setback from the boundary to clear this limit; the Ecodan typically passes at 1.5-2m. For terraced houses or close-spaced semis where boundary setback is constrained, the 7001i may need acoustic enclosure (£500-£1,500) or full planning permission instead of permitted development.

For detached homes with wide gardens, the noise difference is academic. For installs within 4m of a neighbour's window or boundary, it's potentially the deciding factor.

Both have credible UK MCS-registered installer networks but with different DNAs.

Worcester Bosch: the installer base overlaps heavily with the Worcester Greenstar gas-boiler engineer pool - many installers have moved into heat pumps as their gas-boiler work declines. The advantage is volume (Worcester has thousands of accredited engineers); the disadvantage is that heat pump installs require different skills from gas boilers, and not every Worcester-accredited engineer has accumulated significant heat pump experience yet. Worcester's 10-year warranty available via the accredited installer scheme requires the installer to be specifically trained on Compress range heat pumps, not just on gas boilers.

Mitsubishi Ecodan: the installer base is more specifically heat-pump-trained because Mitsubishi has been investing in installer training since 2009. Lower overall installer count but higher proportion of heat-pump-specific experience. The MCS product list shows Ecodan as the UK's most-installed premium heat pump model.

The practical advice: get three quotes from MCS-registered installers in your postcode. Ask each installer how many of the specific model they've installed in the past 12 months. A Worcester-accredited installer with 30+ recent Compress installs is as credible as a Mitsubishi-trained installer with the same volume; both beat any installer with fewer than 10 of the same model recently.

Pick Worcester Bosch 7001i if: you're replacing a Worcester Greenstar gas boiler and want to keep the same installer relationship, you specifically want the hybrid-with-gas-backup option (and accept losing the BUS grant), you value brand familiarity for resale or peace of mind, or you can get a Worcester-accredited installer offering the 10-year warranty scheme.

Pick Mitsubishi Ecodan if: efficiency and noise are your priorities, your install will be within 4m of a neighbour's window or boundary, you want the UK's most-installed premium heat pump (deepest installer experience base), you're going full-replacement (no hybrid) to keep the £7,500 BUS grant, and you have £1,000-£2,000 of budget headroom over the 7001i.

For most 2026 UK buyers going full-replacement on a 3-4 bed semi or detached home, the Ecodan is the right pick on the spec sheet. The 7001i wins specifically in hybrid scenarios and where brand-trust matters more than spec.