Why add battery storage for solar panels?
Solar panels make most of their electricity in the middle of the day. Many UK homes use more electricity in the morning and evening. Without a battery, surplus daytime generation is often exported under the Smart Export Guarantee (SEG). Export rates are set by suppliers and must be above zero, but they are often lower than the price you pay to buy electricity back later. Check your own import and export rates.
Home solar battery storage keeps more of that daytime surplus for the evening. You still export what the battery cannot store. The goal is higher self-use of your own generation, plus the option to top up from cheap off-peak grid electricity on a time-of-use tariff.
AC-coupled retrofit vs DC or hybrid
When people talk about solar panels and battery storage, the coupling method matters more than the brand name on the box.
AC-coupled (typical retrofit)
An AC-coupled battery connects through your home's AC wiring. Your existing solar inverter stays in place. The battery has its own inverter (or an all-in-one unit that includes one). This is the usual route for adding battery storage to existing solar panels, because you are not rebuilding the DC side of the PV system.
DC-coupled or hybrid
A DC-coupled or hybrid setup ties the battery into the solar DC circuit, often through a hybrid inverter. That can be efficient when you are installing solar and storage together. As a retrofit it usually means changing or adding hardware on the DC side, so it is a bigger job than a straightforward AC add-on.
How to size a battery against solar generation and evening use
The right size depends on three things you can check without guessing industry averages:
- Evening and overnight use. Look at smart meter or bill data for how many kWh you use after sunset and before cheap overnight rates start.
- Daytime surplus. Ask your installer (or check your inverter app) how much you typically export on a clear day. That surplus is what a battery can capture first.
- Tariff shape. On a time-of-use tariff such as Octopus Go, you can also charge overnight and discharge during the day rate window. On a flat rate, tariff shifting does not help; solar self-use is the main battery benefit.
A useful starting point for many homes is enough usable capacity to cover a typical evening, then expand later if needed. Habo's 5 kWh EcoFlow STREAM is a common first step, and EcoFlow lists expansion options on the STREAM AC 5000 product page. Oversizing so the pack rarely empties means you paid for capacity you do not cycle. For a deeper walkthrough, see what size battery you need.
G98 vs G99 when you add a battery to solar
In Great Britain, connecting generation and storage in parallel with the public low-voltage network follows Engineering Recommendations published via the ENA document catalogue. EREC G98 covers Fully Type Tested micro-generators up to and including 16 A per phase (about 3.68 kW on a single-phase 230 V supply). Systems outside that scope generally follow EREC G99, which usually needs DNO assessment before connection.
For a qualifying single-premises G98 install, the usual pattern is connect and notify: the installer commissions the equipment, then notifies the DNO within 28 days of commissioning (EcoFlow UK summary of G98 vs G99). G99 flips the order: approval first, then energise.
Adding an AC-coupled battery to existing solar can change the answer, because the DNO looks at aggregate generating capacity and Type Test evidence at the property, not the battery's kWh in isolation. Your installer should check the existing solar notification or connection offer before assuming you stay on G98. For the application path, see G99 application for a home battery and UK home battery installation rules.
EcoFlow lists up to 2,500 W grid-tied output for a single STREAM AC 5000 (3,000 W with an Expansion Battery), and up to 3,000 W for a STREAM 5000 with solar connected (EcoFlow UK specs). Both sit under the typical 3.68 kW single-phase G98 threshold, but existing solar on the same supply still counts, so the electrician confirms the route.
Costs: battery storage for solar panels in the UK
Habo Energy installs a 5 kWh EcoFlow STREAM from £2,499 fully installed, electrician-wired to the consumer unit (G98 / BS 7671). That is an installed price, not a kit-only price. For a sourced cost table including EcoFlow UK kit list prices, see our home battery storage cost guide.
Under HMRC's VAT Notice 708/6, installed home batteries (including batteries retrofitted to solar, and standalone batteries storing grid electricity) are zero-rated at 0% VAT until 31 March 2027, then the reduced 5% rate for installed batteries. Supply-only purchases without installation are treated differently, so read the quote carefully.
What can you save? Think savings-account interest
Even without counting extra solar self-use, Habo's 5 kWh EcoFlow STREAM on Octopus Go saves up to about £450 to £530 a year in the best case, with a best-case payback of about 4.7 to 5.5 years on £2,499. That includes an assumed 90% round-trip efficiency (EcoFlow does not publish a STREAM figure, so we state the assumption). Real savings will be lower. There is no saving from tariff shifting on a flat rate. See how we worked it out.
Frame that yearly saving like the interest you would earn on the same money in a bank savings account. Best case, about 18% to 21% equivalent on £2,499 (the precise simple range is 18.1% to 21.1%). Full workings, including why the like-for-like return is lower because you do not get the capital back, are in home battery vs savings account.
Solar can add to that by storing daytime surplus instead of exporting it cheaply, but the extra amount depends on your roof, your evening load and your SEG rate. Ask for an estimate based on your own generation and bill data rather than a generic percentage.
Do you need solar to benefit from a home battery?
No. A battery can charge from cheap overnight grid electricity and power the home later. That is why Habo systems work with or without solar. If you do not have panels yet, read battery storage without solar.
If you already have panels, the same battery can take solar surplus by day and cheap grid units overnight. That combination is home solar battery storage at its most useful.
SEG, MCS and what Habo does (and does not) sell
The Smart Export Guarantee pays eligible generators for exported renewable electricity. Eligibility and certification rules are set out by Ofgem and your SEG licensee. MCS (or an equivalent scheme your licensee accepts) is commonly part of solar export eligibility. Habo systems are electrician-wired to G98 / BS 7671. The battery hardwire itself is not sold as an MCS package. If you need SEG on solar export, confirm certification with your solar installer or SEG licensee.
What Habo offers
- Electrician-wired EcoFlow STREAM, from £2,499 installed
- 5 kWh starting capacity, with expansion options listed by EcoFlow
- Designed to work with existing solar or without panels
- Not a plug-in battery claiming to feed a whole home from a socket
- Coverage: Habo will try to serve anyone who registers in an area where we have an electrician
- Join the waitlist at /reserve. Nothing to pay today
Warranty terms are set by EcoFlow. STREAM products are listed with a 10-year warranty on EcoFlow's UK warranty policy page.
Frequently asked questions
Yes. This is the usual route for a retrofit: an AC-coupled battery that connects through the home AC system and leaves the existing solar inverter in place. Your installer should still check the existing DNO paperwork, because adding a battery inverter can change the aggregate generation the network sees.
It depends on the aggregate Registered Capacity of generation and storage at the property, and on Type Test evidence. ENA's EREC G98 covers Fully Type Tested micro-generators up to and including 16 A per phase (about 3.68 kW on a single-phase 230 V supply) (ENA Docs). Above that, or outside G98 conditions, EREC G99 applies and usually needs DNO approval before connection. EcoFlow lists up to 2,500 W grid-tied output for a single STREAM AC 5000 (3,000 W with an Expansion Battery), and up to 3,000 W for a STREAM 5000 with solar connected (EcoFlow UK). Both sit under the typical 3.68 kW single-phase G98 threshold, but existing solar on the same supply still counts, so the electrician confirms the route.
Without relying on solar export, a 5 kWh EcoFlow STREAM on Octopus Go saves up to about £450 to £530 a year in the best case, a best-case payback of about 4.7 to 5.5 years on £2,499, including an assumed 90% round-trip efficiency (homepage maths). That is like earning about 18% to 21% on £2,499 in a savings account in the simple best case (full comparison). Real savings will be lower, and there is no saving from tariff shifting on a flat rate. Solar can add further value by storing daytime surplus for evening use, but that extra amount depends on your roof and usage.
Habo Energy installs a 5 kWh EcoFlow STREAM from £2,499 fully installed, electrician-wired to the consumer unit. Installed home batteries are zero-rated for VAT (0%) until 31 March 2027 under HMRC VAT Notice 708/6, then the reduced 5% rate for installed batteries. Kit-only prices do not include an electrician. See home battery storage cost.
No. You can charge from cheap off-peak grid electricity on a time-of-use tariff and use that energy later. Habo's systems are designed to work with or without solar. See our guide to battery storage without solar.
Installed home battery storage systems in residential properties currently benefit from 0% VAT in the UK until 31 March 2027 under HMRC VAT Notice 708/6. After that, installed batteries revert to the reduced 5% rate. A battery bought supply-only, without installation, is treated differently, so check the quote.
Ready to add storage to your solar?
Get an electrician-wired EcoFlow STREAM from Habo Energy, from £2,499. Works with existing solar panels or on its own. Habo will try to serve anyone who registers in an area where we have an electrician. Nothing to pay today.
Join the waitlist