For almost every UK home adding storage to a solar system, lithium iron phosphate (LFP) is the better choice. It lasts 10-15 years against 3-7 for lead-acid, gives you roughly double the usable energy from the same rated capacity, and loses far less of what you put into it. Lead-acid costs less on day one, and that is more or less where its advantage stops.
Both chemistries do the same basic job. They hold the solar electricity your house doesn't use during the day so you can use it in the evening instead of buying it back from the grid. Where they differ is in how much of that stored energy you actually get back, how many times you can do it, and what the whole thing costs you across a decade rather than on the day of install.
What are lithium solar batteries?
Lithium iron phosphate (LiFePO₄, usually shortened to LFP) is the standard chemistry for home storage in the UK now. It reached commercial markets in the early 2000s and has taken over residential storage as costs have come down.
What it does well:
- Cycle life. Commonly quoted at 6,000-10,000 full cycles, which for a battery cycled once a day is well past the 10-year mark.
- Efficiency. Round-trip efficiency of 90-95%, so very little of what you store is lost getting it back out.
- Low maintenance. Sealed units with a built-in battery management system (BMS) handling overcharge, over-discharge and temperature protection.
- Size. Considerably more compact than lead-acid for the same usable capacity, which matters if the battery is going in a utility cupboard rather than a garage.
LFP is also the more thermally stable lithium chemistry. It's less prone to thermal runaway than the NMC and NCA variants used in some older or imported products.
What are lead-acid solar batteries?
Lead-acid is 19th-century technology with very well understood chemistry and a mature supply chain. For solar storage you'll usually see sealed AGM or Gel types rather than flooded, though flooded still turns up in off-grid setups.
What it does well:
- Upfront price. Entry-level systems can come in at around half the cost of a lithium equivalent of the same rated capacity.
- Track record. Decades of service in off-grid, marine and standby power.
- Familiarity. Widely available, and most installers have worked with it.
- Recyclability. Lead-acid is one of the most recycled products in the world, with UK recycling rates for these batteries reported above 95%.
How do they compare at a glance?
| Factor | Lithium (LFP) | Lead-acid (AGM / Gel / flooded) |
| Best for | Daily cycling, long-term solar storage, tight spaces | Budget backup, occasional use, outbuildings |
| Installed cost (5-10 kWh) | £3,000-£8,000 | £2,000-£4,000 |
| Lifespan | 10-15 years | 3-7 years, shorter under daily deep cycling |
| Cycle life | 6,000-10,000 | Roughly 500-1,500 |
| Round-trip efficiency | 90-95% | 70-85% |
| Usable depth of discharge | 80-100% | Around 50% |
| Typical warranty | 10 years | 2-5 years |
| Maintenance | Minimal | Regular checks needed |
What do they cost?
A 5 kWh lithium battery runs roughly £3,000-£5,000 installed, and a 10 kWh system around £5,000-£8,000. Quotes vary a lot by installer, by how much rewiring your property needs, and by whether the battery goes in alongside a new solar array or gets retrofitted to an existing one. Published market ranges for the same sizes span anywhere from £2,500 to £9,500, so get more than one quote and compare what's actually in the price.
A Tesla Powerwall 3 at 13.5 kWh sits at the premium end, generally £7,000-£10,500 installed depending on the installer and the site.
Lead-acid of the same rated capacity comes in around £2,000-£4,000. The catch is in the word "rated". Because lead-acid can only safely give up about half its capacity, a 10 kWh lead-acid bank behaves like a 5 kWh one. To match the usable energy of a 10 kWh lithium battery you need roughly 20 kWh of lead-acid, and most of that price gap disappears.
Then there's replacement. A lead-acid bank cycled every day may need replacing two or three times inside the working life of one lithium battery. Add the lower efficiency, meaning more of your generation is lost as heat on every cycle, and lead-acid frequently ends up costing more per usable kWh over the same period.
There's 0% VAT on battery storage in Great Britain until 31 March 2027, after which it's set to rise to 5% unless the government extends it (Solar Energy UK). That applies to battery-only retrofits as well as batteries fitted alongside panels. Fitting a battery at the same time as solar panels usually costs less than doing it in two visits, since you're paying once for scaffolding and labour.
Verdict: lithium. Lead-acid only makes sense on cost where the budget is a hard constraint and the battery won't be cycling daily.
How long does each one last?
Lithium lasts around 10-15 years in a UK home. Lead-acid lasts 3-7, and the low end of that is what you should expect under daily solar cycling.
Batteries will need replacing before your panels do, so the gap matters. Most lithium systems carry a 10-year warranty that guarantees a minimum capacity retention at expiry, usually 70-80%, often with a throughput cap on total kWh cycled. Read that throughput figure. On a heavily cycled system it can be reached before the 10 years are up.
Lead-acid warranties run 2-5 years and tend to come with conditions attached: shallow cycling only, proper charge profiles, controlled temperature. Daily deep cycling is exactly the pattern that accelerates capacity fade in lead-acid, and it's also exactly what a solar battery is for. That combination makes warranty claims harder than they look.
More on how discharge depth drives this in our guide to depth of discharge and battery lifespan.
Verdict: lithium. Three to four times the service life, stronger warranty terms, better capacity retention.
How much of your stored energy do you actually get back?
Round-trip efficiency is the share of energy you get out compared with what you put in. Lithium manages 90-95%, with some LFP systems quoted as high as 98%. Lead-acid manages 70-85%. So on a lead-acid system, somewhere between a seventh and a third of your stored solar is lost as heat before it ever reaches an appliance.
Depth of discharge (DoD) is the other half of the picture, and the gap is wider. Lithium typically allows 90% or more, so a 10 kWh battery gives you around 9 kWh to use. Lead-acid is limited to about 50%, so the same 10 kWh rating gives you about 5 kWh. Push it deeper and you shorten its life sharply.
Most UK homes end up somewhere between 5 kWh and 15 kWh of storage. What matters when comparing products is usable capacity, power rating and warranty terms, not the headline number on the datasheet. Our guide on choosing the right size solar battery walks through how to work that out for your own consumption.
Verdict: lithium. Nearly double the usable capacity from the same rated size, plus 10-25 percentage points more efficiency. Lead-acid's lower efficiency means buying a bigger system to store the same usable energy, which eats the cost saving.
What maintenance and safety issues should you expect?
Lithium LFP is close to fit-and-forget. Sealed units, integrated BMS handling charge regulation, cell balancing and temperature monitoring, and remote monitoring through an app on most modern systems. Installation still has to meet UK standards for ventilation, overcurrent protection and siting, which is an installer responsibility rather than an ongoing one for you.
Lead-acid asks more. Flooded types need electrolyte top-ups, equalisation charges and monitoring to head off sulphation. Sealed AGM and Gel are less demanding but still sensitive to incorrect charge profiles, overcharging, undercharging and temperature extremes. Lead-acid can vent hydrogen, which is a ventilation consideration, and the units are heavy enough to constrain where they can go.
For a typical household adding storage to an existing array, that difference is the practical one. Lead-acid maintenance is perfectly manageable for an off-grid enthusiast and a poor fit for everyone else.
Verdict: lithium. Near-zero maintenance and better safety characteristics for a domestic setting.
So which should you choose?
Go lithium if the battery will cycle most days, you want it to last a decade or more without attention, space is limited, or you're pairing it with an EV or heat pump. It also scales better if you think you'll add capacity later.
Go lead-acid if the budget is tight and the battery is for occasional or standby use rather than daily cycling. An outbuilding, an off-grid cabin, or emergency backup where it sits at full charge most of the year. It suits people who don't mind doing maintenance and accept replacing it every few years.
For most homeowners across the South and South East, LFP is the one that makes sense. Without a battery, a typical household directly uses only 20-40% of what its panels generate, because generation peaks in the middle of the day when the house is empty. A well-sized battery commonly lifts that to 60-80%, so far more of your own generation goes into your own home rather than being exported at a lower rate than you'd pay to buy it back.
On savings, a well-matched battery on a solar system typically saves somewhere in the region of £300-£600 a year, though that depends heavily on your usage, generation, tariff and energy prices at the time. Published payback estimates vary widely, commonly landing between 8 and 15 years, and the biggest single variable is usually your tariff structure rather than the battery itself.
At CRG Direct we size and fit battery systems across the South and South East, from survey through to handover and aftercare, and we can talk you through which grants you might qualify for.
Frequently asked questions
Can I upgrade from lead-acid to lithium later?
Yes, but it isn't a straight swap. You'll usually need a compatible inverter or charge controller, updated wiring, and in most cases a new battery management setup. The total often approaches the cost of a fresh lithium install, so if lithium is where you expect to end up, going there first is generally the cheaper route. An installer can assess your existing setup and tell you what would need changing. We've covered the general case in adding a battery to an existing solar system.
How do battery costs compare with what you save on grid electricity?
A well-sized lithium battery typically saves in the region of £300-£600 a year by shifting solar into the evening and letting you charge cheaply on a time-of-use tariff, though this varies with your usage, generation and energy costs. Payback estimates commonly range from 8 to 15 years. Lead-acid's 3-7 year life and lower efficiency mean that under daily cycling it often doesn't last long enough to recover its cost, which is the main reason it has largely disappeared from UK domestic installs.
What size battery do I need?
The average UK home uses 8-10 kWh a day, but the number that actually drives battery sizing is how much you use after the sun goes down. A three-bed house in the South East might get through 3-5 kWh between 5pm and 10pm, which a 5-10 kWh battery covers comfortably. Add a heat pump or an EV and you're looking at 13-20 kWh. Oversizing stretches out the time to recover the cost, so it's worth sizing against real consumption data rather than guesswork. There's more detail in our battery sizing guide, and our battery cost breakdown covers pricing by capacity.
Are there grants for solar battery installation?
There's 0% VAT on battery storage until 31 March 2027 across Great Britain. Beyond that, the Warm Homes: Local Grant in England offers up to £15,000 per property for energy performance measures, and solar panels and battery storage are on the eligible list, plus a separate cap of up to £15,000 for low-carbon heating (Energy Saving Trust). It's income-assessed and delivered through local councils, and GOV.UK sets the main conditions as an EPC of D to G and a household income usually of £36,000 a year or less. Scotland, Wales and Northern Ireland run their own schemes. We can check what you're likely to be eligible for before you commit to anything.