Hybrid inverter architecture, DC versus AC coupling, battery sizing and grid interaction strategy: this page covers the engineering side of a combined solar and battery system, for homeowners and their advisers who want to understand how it is actually specified rather than the household outcomes covered on our solar and battery project planning page. The technical starting point is an assessment of your roof, consumer unit and consumption profile. When solar and battery are specified together, the hybrid inverter can be sized to manage both generation and storage through a single point of control. DC power from the panels flows directly into the battery without a conversion step, which typically delivers higher round-trip efficiency than an AC-coupled retrofit. The system manages generation, storage, dispatch, tariff scheduling and grid interaction as a unified programme. In summer, surplus solar fills the battery for evening and overnight use. In winter, when solar yield is lower, the system can switch to grid charging on off-peak tariffs automatically. Battery performance and financial return depend on system design, tariff structure, usage profile and electrical infrastructure. We model these factors before specifying equipment. Solar plus battery can also improve resilience during a power cut, but only when backup capability, such as EPS switching, battery capacity and inverter output, has been specifically designed for that purpose. For an overview of the full battery range, visit our battery storage hub. If you already have solar and want to add a battery, see battery retrofit for existing solar. For payment and finance routes, see smart financing options.
In a DC-coupled system, a single hybrid inverter handles both solar conversion and battery management. Pure DC power from the panels charges the battery directly without the double conversion penalty of a retrofit AC-coupled system. The result is 96 to 97 percent round-trip efficiency versus 90 to 92 percent for separate components - a 5 to 7 percent efficiency advantage that compounds across every kilowatt-hour generated over a 25-year asset life. For example, a Surrey 8kWp array generating 7,200 kWh annually could recover an additional 360 to 500 kWh per year through this efficiency differential - worth approximately 90 to 175 GBP in avoided grid imports at current rates, with no additional hardware required.
A standalone battery provides backup power until it depletes - typically 12 to 24 hours under luxury estate consumption. A DC-coupled hybrid system can significantly extend this. During a grid outage, the hybrid inverter island-switches the property in under 20 milliseconds and continues managing the solar array independently. While the grid is down, your panels continue charging the battery in island mode throughout the day. In a Surrey summer with 8 or more hours of usable solar generation per day, the microgrid can sustain whole-estate supply for extended periods - with no generator fuel, no noise, no maintenance, and no manual intervention - though actual duration depends on weather and household consumption. Security arrays, Control4 automation, climate control, and server infrastructure are designed to remain powered through typical grid failure durations.
Some residential solar, battery storage and qualifying energy-saving installations may be eligible for 0% VAT, subject to current HMRC rules and confirmation at quotation. Where battery storage and solar panels are installed as a single concurrent programme and the project qualifies, the zero rate can apply to the full hardware stack and installation labour - hybrid inverter, battery modules, solar panels, mounting system, DC cabling, consumer unit amendments, and engineer time. For example, on a Surrey hybrid system investment in the region of 18,000 to 28,000 GBP, this could represent an indicative saving of approximately 3,600 to 5,600 GBP at invoice where eligible. We confirm the correct VAT treatment in writing at quotation stage before any commitment is made.
We retrieve your half-hourly Smart Meter consumption data and model roof irradiance from your specific postcode, pitch, and orientation. We map the generation surplus against your evening demand curve to establish the optimal array size and battery capacity for maximum self-consumption and arbitrage return.
We select the hybrid inverter platform for confirmed Octopus API compatibility, battery expansion support, and reliable EPS operation. The solar array is designed concurrently - string layout, module-level optimisation, and DC cable topology all engineered to the specifications of the chosen hybrid inverter for maximum system coherence.
Our qualified engineers install the solar array, hybrid inverter, and battery as one co-ordinated programme, with certification handled by appropriately qualified professionals where required. One DNO G98/G99 submission, one scaffolding mobilisation, and one commissioning and compliance sign-off cover the full hardware stack and installation labour, with the appropriate VAT invoice confirmed at quotation stage.
We configure Octopus Intelligent scheduling, verify solar surplus capture and EPS island-switching are operating correctly, complete Smart Export Guarantee registration in your name, and issue all manufacturer warranty documentation before engineers leave. Your microgrid is live and financially optimised from commissioning day.
In a DC-coupled system, pure DC power from the solar array flows directly into the battery without conversion - eliminating the 5 to 7 percent efficiency penalty of an AC-coupled retrofit.
A single hybrid inverter handles both solar conversion and battery management. There is no AC-to-DC-to-AC conversion cycle. Tesla Powerwall 3, SolarEdge Home Hub, and GivEnergy AIO are all DC-coupled platforms where the inverter and battery share a single DC bus - generation, storage, and dispatch managed by one intelligence layer through one app.
Battery capacity is sized against your actual half-hourly consumption curve, your roof's seasonal irradiance profile, and your resilience requirements - not against a generic kWh default.
We retrieve 12 months of Smart Meter half-hourly data and model your load curve across every month of the year. A Surrey 5-bedroom property with a heat pump, EV charger, and home office has a fundamentally different battery sizing requirement from a SW London townhouse. We calculate the capacity that maximises solar self-consumption, sustains overnight discharge, and maintains your required EPS reserve hours simultaneously.
A standalone battery provides backup until it depletes. A DC-coupled hybrid system can significantly extend that duration - the solar array continues recharging the battery in island mode throughout any grid failure.
During a grid outage, the hybrid inverter island-switches the property in under 20 milliseconds. The solar array continues operating and charging the battery autonomously while the grid is down. In a Surrey summer with 8 or more usable generation hours per day, the microgrid can sustain whole-estate supply for extended periods - with no diesel, no noise, and no manual intervention - though actual duration depends on weather and consumption.
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In winter, when Surrey solar generation drops to 1.5 to 2.5 kWh per day, the hybrid brain automatically shifts to grid trading mode - filling the battery overnight at 7 to 9p/kWh and dispatching during peak hours at 25 to 35p.
The hybrid inverter connects to the Octopus Energy API and receives half-hourly pricing data 24 hours in advance. It schedules battery charging during the cheapest overnight windows automatically. No timers, no manual management, and no seasonal adjustment required from you. Annual tariff reviews ensure the configuration remains optimal as pricing structures evolve.
"We installed a full SolarEdge Home Hub system with an 8kWp array and 9.7kWh battery. The DC-coupled architecture was explained clearly and the efficiency difference versus a retrofit is measurable in the monitoring data. Self-consumption is running at 88 percent since commissioning in April. The installation was immaculate - no visible cabling anywhere and the utility room setup looks like something from a data centre."
"Tesla Powerwall 3 with a 10kWp array. The solar-recharged backup capability was the key decision factor for us - we have a Control4 system, NAS servers, and CCTV that cannot afford any downtime. During the installation, the team tested the EPS island-switch before leaving. The transition is genuinely imperceptible. The Octopus Intelligent configuration was set up on commissioning day and the battery has been running autonomously ever since."
For a new combined installation, DC-coupling through a hybrid inverter is generally the technically preferable choice. The typical 5 to 7 percent efficiency advantage over AC-coupling compounds across every kilowatt-hour over the system's lifetime. For example, a Surrey 8kWp array generating 7,200 kWh annually could recover an additional 360 to 500 kWh per year through this efficiency differential at no additional capital cost - worth approximately 90 to 175 GBP per year in avoided grid imports at current rates. We specify DC-coupled hybrid platforms as our standard recommendation for new combined battery and solar installations.
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Capacity in kWh determines how long your estate runs on stored energy. Power in kW determines how many loads you can run simultaneously during discharge or EPS operation. A 13.5kWh battery with a 5kW power output cannot simultaneously power an induction hob at 7kW and an EV charger at 7.4kW. We model both the capacity requirement for your overnight and backup duration, and the peak power requirement for your simultaneous loads, before specifying any system.
Where battery storage and solar panels are installed as a single concurrent programme, the zero rate can extend to panels, hybrid inverter, battery modules, mounting hardware, DC cabling and installation labour, subject to eligibility and quotation-stage confirmation. For example, on an 18,000 to 28,000 GBP Surrey hybrid system, this could save in the region of 3,600 to 5,600 GBP at invoice where eligible - the exact figure is confirmed at quotation stage and built into the savings estimate we provide before any commitment is made.
A DC-coupled hybrid system uses a single inverter to manage both solar generation and battery charging on the DC side of the circuit. Pure DC power from the panels charges the battery directly without the double conversion penalty of an AC-coupled retrofit. Round-trip efficiency is typically 96 to 97 percent versus 90 to 92 percent for AC-coupling - an advantage that compounds across every kilowatt-hour over the system's lifetime. For new combined installations, DC-coupled hybrid architecture is generally the more efficient and cost-effective choice.
The solar-recharged EPS capability of a DC-coupled hybrid system can offer a meaningful resilience advantage over a standalone battery. During a grid outage, the hybrid inverter island-switches your property in under 20 milliseconds. Your solar array continues generating and recharging the battery autonomously in island mode. In a Surrey summer with 8 or more usable generation hours per day, this can significantly extend whole-estate supply without manual intervention, though actual duration depends on weather and consumption. In winter, backup duration is limited to battery capacity - typically 12 to 24 hours under standard luxury estate consumption - which we model against your specific critical load profile during the pre-installation audit.
Yes. Every hybrid platform we specify supports modular battery expansion. A SolarEdge Home Hub, Tesla Powerwall Gateway, or GivEnergy AIO system can accept an additional battery module in year 3 or 5 without replacing the inverter or disrupting the existing installation. This is particularly relevant when an EV is added to the household, as the additional overnight charging load typically requires more battery capacity to maintain arbitrage cycling. We size and document the expansion pathway for your specific system at installation.
Some residential solar, battery storage and qualifying energy-saving installations may be eligible for 0% VAT, subject to current HMRC rules and confirmation at quotation. Where battery storage and solar panels are installed as a single concurrent programme and the project qualifies, HMRC can classify the entire installation as a qualifying energy-saving installation, applying the zero rate to the full hardware stack - hybrid inverter, battery modules, solar panels, mounting system, DC cabling, and installation labour. For example, on an 18,000 to 28,000 GBP Surrey hybrid system investment, this could save in the region of 3,600 to 5,600 GBP at invoice where eligible. We confirm the correct VAT treatment and exact saving in writing at quotation stage.
Maximize your investment. Without a battery, you likely export 50-70% of your solar energy back to the grid for pennies.
With a properly sized battery system:
"A battery transforms your home from a passive energy consumer into an active energy hub."