The Strom AuraHeat 9kW Single Phase Stored Combi Boiler (SBSP9SC) combines Strom's self-modulating electric heat exchanger with a 35-litre integrated stainless steel buffer cylinder in a single wall-mounted unit. An automatic diverter valve switches the heat exchanger's output between the central heating circuit and the integral cylinder, so the boiler behaves like a combi for hot water while also driving radiators or underfloor heating. With no flue, zero local carbon monoxide, and near-silent operation, it's designed as a drop-in replacement for off-grid, all-electric, or gas-free properties.
For central heating, the heat exchanger's multiple strands modulate from the full 9kW output down to as little as 1kW to track the property's heat demand. As soon as a hot water tap or shower is opened, the diverter gives priority to the 35L cylinder, in the same way a gas combi prioritises hot water over heating. With the cylinder at full capacity, the boiler supports DHW flow rates of up to 12 litres per minute at an output temperature of up to 55°C (at reduced flow rates); even once the cylinder is fully depleted, the heat exchanger alone continues to deliver up to 7 litres per minute, with the cylinder recovering to full temperature in around 20 minutes.
35L
Stainless Steel Cylinder
12 LPM
Peak DHW Flow Rate
Part P Notifiable Electrical Work
As an electric boiler, connecting the SBSP9SC is notifiable electrical work under Building Regulations. Strom's installation guide requires that the electrical connection is carried out by a competent person registered with a Part P scheme (such as NICEIC), who must issue an electrical installation certificate immediately after the live connection is made. Boiler installations of any fuel type, including electric, are notifiable building work in their own right.
Confirm Electrical Loading Before Specifying
Cylinder capacity (35L), DHW flow rates (12 L/min charged, 7 L/min depleted), maximum DHW temperature, and cylinder reheat time are confirmed for the AuraHeat Stored Combi range. However, the amp draw, minimum breaker size, and minimum cable size for the SBSP9SC have not been confirmed against a model-specific datasheet and remain separate from the figures published for Strom's instant Combi/System range. These should be checked against Strom's AuraHeat installation manual, or by contacting Strom at stromltd.com, before finalising a circuit design or quotation.
Buffer Cylinder vs. Instant-Only Combi
Strom's standard Combi range (SBSP7C / SBSP11C / SBSP15C) heats domestic hot water instantaneously with no storage, so peak flow rate is limited to whatever the heat exchanger alone can deliver. The AuraHeat Stored Combi adds a 35L stainless steel buffer cylinder ahead of the heat exchanger, so with the cylinder charged the boiler can support a higher peak flow rate (up to 12 L/min) than an instant-only unit of the same kW rating - while still falling back to a strong 7 L/min instant supply once the buffer is depleted, recovering in around 20 minutes.
Patented Multi-Strand Heat Exchanger
Strom's heat exchanger spreads the heating load across multiple independent heating strands rather than a single element, with heat transferred evenly across the whole surface area. This eliminates the hotspots that cause limescale to bake onto an element and shorten its life, and because the water circuit is kept physically separate from the strands themselves, corrosion is reduced and any strand can be replaced individually rather than swapping the whole heat exchanger.
Self-Modulating Down to 1kW
Because each heating strand can be switched independently, the boiler tracks demand in fine steps across its 9kW output range, modulating down to as little as 1kW. This reduces cycling, helps maintain a steadier room temperature, and avoids the abrupt on/off behaviour associated with single-element electric boilers.
35-Litre Stainless Steel Buffer Cylinder With Integrated Coil
The integral cylinder is heated indirectly via an integrated coil rather than direct immersion, keeping domestic hot water separated from the heat exchanger's heating strands. This significantly increases scale resistance in hard water areas, since any limescale forms on the coil rather than fouling the heating elements themselves, helping protect the heat exchanger's output over the life of the boiler.
Automatic Diverter Valve for Heating or Hot Water
A built-in diverter automatically switches the heat exchanger's output between the central heating circuit and the 35L cylinder. When a hot water demand is detected, the diverter prioritises the cylinder - just as a gas combi prioritises hot water over heating - then returns output to the heating circuit once the demand ends.
Programmable Hot Water Priority
Programmable parameters let installers and users prioritise stored volume, instantaneous flow rate, or a balance of both. A household with occasional long showers may benefit from prioritising volume to keep the cylinder topped up, while one with frequent short draw-offs may prefer prioritising flow rate for faster recovery between uses.
Flue-Free, Zero Carbon Monoxide Operation
With no combustion taking place, the AuraHeat range produces zero local carbon monoxide and needs no flue terminal, soffit clearance, or terminal guard. This opens up siting options a gas or oil boiler couldn't use, including internal cupboards, flats, and properties where external wall access for a flue isn't practical.
Touchscreen Control With a Familiar Layout
The on-board touchscreen display mirrors the layout installers and homeowners already know from gas, oil, and LPG boilers, showing heating and hot water status, current temperature, and a weekly programmer. This means handover to the end user doesn't require retraining on an unfamiliar interface.
Built for Off-Grid and Renewable Setups
Strom's electric boiler range is designed to sit alongside solar PV generation and time-of-use tariffs such as Economy 7/10, letting the cylinder be heated during cheap-rate or self-generated periods and drawn down later in the day - a configuration not available to instant-only combi boilers.
| General |
| Manufacturer |
Strom Limited |
| Range |
AuraHeat Stored Combi |
| Manufacturer Part Number (MPN) |
SBSP9SC |
| Boiler Type |
Electric Stored Combination Boiler with 35L integrated stainless steel buffer cylinder |
| Heat Output |
9kW |
| Larger Sibling Model |
SBSP13SC (13.5kW, same AuraHeat Stored Combi design) |
| Electrical Supply |
| Phase |
Single Phase |
| Supply Voltage |
230VAC |
| Amps / Minimum Breaker / Minimum Cable Size |
Confirm against Strom's AuraHeat installation manual * |
| Heating Performance |
| Heating ErP Rating |
D * |
| Max. Heating Flow Temperature |
80°C * |
| Min. Heating Flow Temperature |
20°C * |
| Max. Heating Pressure |
1.5 bar * |
| Min. Heating Pressure |
0.5 bar * |
| Hot Water Performance |
| Hot Water Storage |
35-litre stainless steel buffer cylinder with integrated coil |
| DHW Flow Rate - Cylinder Fully Charged |
Up to 12 L/min |
| DHW Flow Rate - Cylinder Depleted |
Up to 7 L/min |
| Max. DHW Output Temperature |
Up to 55°C (at reduced flow rates) |
| Cylinder Reheat Time |
Approx. 20 minutes |
| Diverter Valve |
Integrated, automatic central heating / DHW switching |
| Dimensions & Installation |
| Dimensions (H × W × D) |
920 × 570 × 300mm |
| Flue Required |
No |
| Pump & Expansion Vessel |
Integrated within the boiler casing |
* Figures marked with an asterisk reflect Strom's published range-wide specifications for single-phase electric boilers and have not been verified against a model-specific datasheet for the AuraHeat SBSP9SC at the time of writing. Confirm electrical loading (amps, minimum breaker, minimum cable size) and heating pressure/temperature limits against Strom's AuraHeat installation and user guide, or by contacting Strom Limited directly, before specifying or installing.
What is a "stored combi" boiler, and how is it different from a normal combi?
A combi (combination) boiler normally heats domestic hot water instantaneously as it passes through, with output limited to whatever the heat exchanger alone can deliver. A stored combi, like this AuraHeat model, adds a 35-litre stainless steel buffer cylinder ahead of the heat exchanger, allowing higher peak flow rates (up to 12 L/min) when the cylinder is charged, while still providing a strong 7 L/min instant supply once it's depleted.
Does the Strom AuraHeat 9kW need a flue?
No. As an electric boiler there is no combustion, so no flue, terminal, or soffit clearance is required. It still needs to be wall-mounted with adequate clearance around the casing for servicing and ventilation, as set out in Strom's installation guidance.
What's the difference between the SBSP9SC and SBSP13SC?
Both are part of the AuraHeat Stored Combi range and share the same integrated-cylinder design and 920 x 570 x 300mm casing. The SBSP9SC delivers 9kW of heat output, while the SBSP13SC steps this up to 13.5kW for properties with a higher heat loss or hot water demand. Both are single-phase, 230V units.
How does the boiler manage central heating and hot water at the same time?
The AuraHeat Stored Combi uses a built-in diverter valve to direct the heat exchanger's output. During normal operation it heats the central heating circuit and keeps the 35L cylinder topped up; as soon as a hot water tap or shower is opened, the diverter switches priority to the cylinder to meet the DHW demand, then reverts to heating once the demand ends - the same priority logic used by gas combi boilers.
What happens to hot water flow and temperature if the cylinder runs low?
With the 35L cylinder fully charged, the boiler supports DHW flow rates of up to 12 litres per minute at up to 55°C (at reduced flow rates). If the cylinder becomes depleted during heavy or prolonged use, the heat exchanger continues to supply hot water directly at up to 7 litres per minute, so the household isn't left without hot water - the cylinder then recovers to full temperature in around 20 minutes.
Will this boiler need annual servicing under unvented cylinder regulations (G3)?
The 35L cylinder is heated indirectly via an integrated coil, but whether the domestic hot water side of the cylinder is vented or unvented determines whether Building Regulations Part G (G3) - and its requirements for a temperature & pressure relief valve, discharge pipework, and annual maintenance - applies. This should be confirmed from Strom's AuraHeat installation documentation before specifying, as it affects the ongoing servicing obligations passed on to the homeowner.
What electrical supply does the SBSP9SC need?
It runs from a single-phase 230VAC supply, in line with the rest of Strom's electric boiler range. The exact amp draw, and the minimum breaker and cable sizes required for a 9kW stored combi unit, should be taken from Strom's AuraHeat-specific installation manual, since connection is notifiable electrical work requiring a Part P certificate.
Can the AuraHeat 9kW be used with solar panels or on an off-grid system?
Strom's electric boiler range, including the AuraHeat Stored Combi, is designed to work alongside solar PV generation and time-of-use tariffs such as Economy 7/10 - the cylinder can store heat generated or bought during cheap-rate periods for use later in the day.
