Integrated Heat Pump
R290 · GWP 3
250 Litres
CoP 3.4
Energy Rating A+
Hot Water in 30 Min
Smart App Control
Duplex Stainless
The Mixergy 250L R290 iHP Integrated Heat Pump Cylinder (MX-250-IH2-579) is the large-capacity model in Mixergy's iHP X R290 range — a smart unvented hot water cylinder with an integrated indoor R290 heat pump requiring no outdoor unit. Combining a Duplex stainless steel cylinder with a top-mounted heat pump head and patented top-down stratified heating, it delivers usable hot water in under 30 minutes — up to 10× faster than conventional integrated HP cylinders — while using around three times less electricity than a direct electric cylinder. Ideal for larger all-electric homes and high-demand properties. The Mixergy app enables machine-learning scheduling, time-of-use tariff optimisation, and live hot water level monitoring.
Recovery & Heat-Up Times (15°C to 50°C)
<30 min
First usable hot water (top-down partial charge)
~195 min
70% charge reheat
~279 min
100% charge reheat
59°C
Max temp — heat pump only
💡 Top-Down Advantage: Mixergy's patented stratification fills from the top down. Hot water is available at the tap in under 30 minutes even from a cold cylinder — dramatically better than conventional HP cylinders that must heat the full volume before any usable water is available.
Key Features
- Integrated indoor R290 heat pump — compact head on top of cylinder, no outdoor unit or separate plant room required
- Top-down stratified heating — usable hot water in under 30 minutes, up to 10× faster than conventional integrated HP cylinders
- CoP 3.4 — ErP A+ rated, ~3× more efficient than a direct electric cylinder
- 250L Duplex stainless steel cylinder — suited to larger households and higher-demand all-electric properties
- R290 (propane) refrigerant — GWP of 3, zero ODP, factory-charged with ~150 g
- Up to 59°C on heat pump alone — sufficient for Legionella prevention without the backup immersion
- 2–3 kW backup immersion heater (1¾" BSP, factory-fitted) for boost and emergency use
- Mixergy app — machine-learning scheduling, Agile/Economy7 tariff optimisation, live level monitoring, Boost mode
- Modular two-piece design — cylinder and heat pump head shipped separately for easier installation in tight plant spaces
- 150mm duct connections (intake and exhaust) — airflow ~500 m³/h; requires external wall access
- Ambient operating range −7°C to +35°C — operable year-round in the UK
- G3 unvented kit included — PRV, check valve, P&T relief valve, expansion relief, tundish, expansion vessel
- 25-year cylinder warranty / 5-year heat pump head warranty (Mixergy standard terms)
- Powerline-to-Ethernet adapter included for broadband connectivity
Top-Down Stratification
R290 GWP=3
Duplex Stainless
ML Scheduling
TOU Tariff Ready
No Outdoor Unit
Technical Specifications
What's Included
250L Duplex stainless steel cylinder
Integrated R290 heat pump head unit
2–3 kW backup immersion heater (factory-fitted)
Unvented G3 kit: PRV, check valve, P&T relief, expansion relief, tundish
Expansion vessel with mounting bracket & 22mm adaptors
Powerline-to-Ethernet adapter & Ethernet cable
Control gauge & onboard electronics
User Guide & iHP X installation/servicing manual
⚠️ Installer Requirements: Must be installed and commissioned by a G3-qualified installer in accordance with Mixergy's iHP X installation manual and current Building Regulations. Electrical connections must comply with BS 7671.
ℹ️ Ductwork: Requires a 150mm air intake duct and 150mm exhaust duct connected to the outside of the building. Both should be insulated. The 250L unit (2,145mm tall) requires additional headroom consideration. Access to an external wall for ductwork is essential.
Frequently Asked Questions
How does recovery time compare between the 210L and 250L models?
Both models deliver usable hot water in under 30 minutes thanks to top-down stratification. The 250L takes approximately 195 minutes for a 70% charge reheat and ~279 minutes for a full 100% reheat (vs. ~164 min and ~234 min for the 210L). The larger volume takes longer to fully recharge, but first availability is the same.
Which households is the 250L best suited to?
The 250L is suited to larger all-electric homes with higher hot water demand — typically 4+ bedrooms or properties with higher simultaneous draw-off requirements. For smaller properties or those with more space constraints, the 210L is often sufficient.
Does it need an outdoor heat pump unit?
No — the R290 heat pump is fully integrated into the cylinder head indoors. Only 150mm air ducts to the outside are required. No outdoor unit, no refrigerant pipework installation, and no F-Gas certification is needed for air circuit commissioning.
What's the difference between the iHP X 210L and 250L?
The two models share identical heat pump head, CoP, and controls. The 250L is 260mm taller (2,145mm vs. 1,885mm), weighs 97 kg empty (vs. 94 kg), and provides 40L more capacity. Recovery times for full and 70% charges are proportionally longer in the 250L.
What warranty applies?
Mixergy standard terms provide a 25-year warranty on the Duplex stainless cylinder and a 5-year warranty on the heat pump head. Registration and installation by a qualified G3 installer is required. Full terms in Mixergy's warranty documentation.
