Solar Battery Storage – Save Surplus, Slash Bills
When your solar panels generate more than your house can use, where does the surplus go? Without storage, straight back to the grid for pennies. With a Welsh Solar battery, it stays in your home – ready for evening, weekend or blackout.
Battery upgrades from £3,995 fitted. AC- or DC-coupled to suit your system. Free survey.
The maths behind battery storage
A typical 4kW solar system in Cardiff produces about 3,800kWh of electricity a year. Without a battery, you will use roughly 35-45% of that yourself and export the rest at the going SEG rate (5-15p depending on tariff). With a 5-10kWh battery, self-consumption jumps to 75-90%.
Put another way: a battery effectively trades export at 7p for avoided import at 26p. Every kWh you can shift from grid to battery is worth roughly 19p. Over a year, that adds up to £400-£700 in extra savings for the average Welsh household.
Battery prices have fallen 40% in the last five years. The combination of cheaper hardware, more efficient LFP chemistry, the Smart Export Guarantee and time-of-use tariffs means storage now pays for itself faster than the panels did when they were first introduced.
AC vs DC coupling – which is right for me?
DC-coupled batteries connect directly to a hybrid inverter and are the most efficient choice for new solar installations – we lose around 5% less energy at each conversion. The hybrid inverter manages both the panels and the battery from one unit.
AC-coupled batteries connect on the alternating-current side of your existing inverter, which makes them the perfect choice for retrofitting onto an existing solar system without replacing any kit. Modern AC batteries like the GivEnergy AIO and Tesla Powerwall 3 are virtually indistinguishable in performance terms.
- Hybrid inverters: Solis, GivEnergy, Fox, SolarEdge
- AC-coupled: Tesla Powerwall 3, GivEnergy AIO, Enphase 5P
- Stackable: Pylontech, Huawei, BYD, Sungrow
- All offer iOS/Android monitoring and remote firmware updates
Time-of-use tariff savings
Once you own a battery, you stop being a price-taker. Smart tariffs let you buy electricity when it is cheap (often under 10p between 23:30 and 05:30) and avoid buying when it is expensive (28-32p during the 16:00-19:00 evening peak). The battery effectively shifts cheap energy into expensive periods.
Octopus Flux, Cosy Octopus, Intelligent Octopus, EDF Sunday Saver and British Gas Peak Save all reward battery owners. Combine these with solar generation and most of our customers see their grid bill fall to standing charges only during the summer.
Future-proof your home
Battery storage is no longer a luxury – it is fast becoming part of any sensible long-term energy strategy. As gas boilers are phased out by 2035, more of your home heat will come from electric heat pumps. A battery sized today with future use in mind will absorb the additional EV and heat-pump loads without needing replacement.
Welsh Solar designs every system to accommodate up to a 20% future load increase as standard. We will tell you on day one which battery is right for your home as it is, and which is right for your home in 2035.
Backup power during Welsh storm season
Power cuts are not unusual in Welsh winters. Storm Ciarán in November 2023 left tens of thousands of homes without power for over 12 hours; smaller cuts of 2-4 hours happen across the country every year. With a battery installed and EPS (Emergency Power Supply) enabled, your home keeps the lights on, fridge running and broadband live – usually transparently, with no flicker.
Welsh Solar offers two levels of backup: whole-home backup (using a Tesla Powerwall 3, Powerwall+ or Enphase IQ8 microinverter setup) and essential-circuits backup (using almost any battery we install, switching critical sockets and lighting only). Whole-home backup is the gold standard but requires careful planning of any heat pumps, EV chargers or showers that might cause overload.
Stackable, future-proof storage
Almost every modern battery we install is stackable. That means you can start with a 5kWh unit today and add another 5kWh module next year if your circumstances change. Adding modules later costs about 20% more per kWh than buying it all up front, but you only pay for capacity when you need it.
Speak to our designer if you anticipate buying an EV, fitting a heat pump or having children leave home in the next five years – any of these will change your optimum battery size and the right base unit choice.
Frequently asked questions
Can I add a battery to my existing solar panels?
Yes – AC-coupled batteries are designed exactly for this. Most retrofits take one day with no need to touch your existing inverter or panels.
How much can a battery save me?
Most Welsh households save £400-£700 a year on grid imports plus £100-£300 from smart tariff arbitrage. Heavy daytime users or EV drivers save more.
Are batteries dangerous?
No. We exclusively install LFP (lithium-iron-phosphate) chemistry which is the safest commercial battery technology. Every unit carries CE/UKCA marking and BS EN 62619 certification.
How long is the warranty?
All batteries we install carry a minimum 10-year manufacturer warranty plus our own 12-month workmanship guarantee.
Do batteries work without solar?
Yes – many customers install batteries solely to take advantage of cheap off-peak tariffs. The payback is slightly slower but still attractive on a smart tariff.