Solar battery storage is back on most Irish quotes since SEAI introduced a €600 battery grant in October 2026 (pv magazine). Whether a battery is worth it for you is covered in our solar battery storage advice page. This guide is about choosing the battery itself: chemistry, size, warranty terms and how to assess the brands installers propose. Checked 26 October 2026.
How solar battery storage works in an Irish home
A battery stores surplus solar electricity from the middle of the day for use in the evening. SEAI notes it can also charge from the grid at a cheaper night rate, and that a battery needs a hybrid inverter, or one planned for a future battery (SEAI Homeowner’s Guide). Some energy is lost in each charge and discharge cycle. The value of storage comes from the gap between what you pay for electricity and what you’re paid to export: the Irish Times cited unit prices of 36c–45c/kWh against export rates around 19.5c.
Battery chemistries: LFP vs NMC
Almost all home batteries now are lithium-ion, but “lithium-ion” covers several chemistries. The two you’ll hear about are lithium iron phosphate (LFP, sometimes LiFePO4) and nickel manganese cobalt (NMC).
| LFP (lithium iron phosphate) | NMC (nickel manganese cobalt) | |
|---|---|---|
| Thermal runaway onset | About 270°C | About 150–210°C |
| Typical cycle life (80% depth of discharge) | 3,000–6,000+ | 1,000–2,500 |
| Expected lifespan | 10–15+ years | 7–10 years |
| Energy density | 90–160 Wh/kg (heavier) | 150–250 Wh/kg (lighter, more compact) |
The practical takeaway: LFP is generally regarded as more tolerant of heat and longer-lived, at the cost of more weight and bulk. A Professional Electrician article by a UK battery maker’s managing director (a commercially interested source) makes the same safety argument for LFP. Older lead-acid batteries are cheaper but less efficient and shorter-lived, according to Energia, and are rarely proposed for grid-tied homes now. Ask every installer which chemistry they’re quoting, and put the answers side by side using our compare solar quotes checklist.
What size battery?
The SEAI battery grant is a flat €600 for a battery of 5kWh or more (SEAI application guide). Sizes are growing: the Irish Times quoted one installer as saying the average battery fitted has risen from 6kWh to 9.6kWh in 18 months. Bigger isn’t automatically better. Think about:
- Your evening use. How many kWh do you use between about 5pm and bedtime? A battery much larger than that may rarely fill or empty fully from solar alone.
- Your surplus. A 3kWp system in December won’t fill a 10kWh battery; in June it might.
- Night-rate charging. If you’re on a smart tariff, a larger battery can charge cheaply overnight in winter.
- Usable vs nominal capacity. Datasheets may list total capacity and a lower usable figure. Compare usable kWh across quotes.
- Power (kW) as well as energy (kWh). The power rating limits how many appliances the battery can run at once.
On cost, Energia (March 2026) gave €1,700–€3,000 for a 5kWh battery and €1,500–€7,000 across sizes, depending on capacity, type and warranty.
Reading the warranty small print
Battery warranties have more moving parts than panel warranties. According to Heatable, a 10-year warranty is typical, some makers offer 12 or 15, and there are often two promises: a product warranty against faults and a performance warranty on capacity retention. Check:
- Years. The headline term, and from when it starts.
- End-of-warranty capacity. For example, 80% retention would leave a 10kWh battery with about 8kWh after the term.
- Throughput limit. Many warranties end after a set amount of energy has passed through the battery, whichever comes first. Heatable lists allowances of roughly 2.5–3.1MWh per kWh of capacity for some makers.
- Permitted uses. Grid-charging on smart tariffs or trading schemes may count differently. Ask if your intended use is covered.
- Registration and installer conditions. Some warranties require registration or an approved installer.
- Who you claim from. The installer, a distributor or the manufacturer, and whether they have an Irish presence.
Keep a copy of the warranty version in force on your installation date.
Brands to ask about, and how to assess them
We don’t rank or recommend brands. You’ll see batteries from inverter makers and battery specialists on Irish quotes. Energy Matters reports that Tesla moved its Powerwall home range to LFP and that BYD, Sungrow and Sigenergy also use LFP. Whatever brand you’re quoted, ask:
- Is this exact model on ESB Networks’ Low Carbon Technology Register? Since 6 January 2025, installers should choose registered devices and quote the reference on the NC6 (ESB Networks).
- Which chemistry is it, and what’s the usable capacity?
- Is it compatible with my inverter, or does it need its own?
- Can I add modules later to expand it?
- What are the warranty years, end capacity and throughput limit?
- Does it offer backup power in a power cut, and does that need extra equipment?
If you haven’t yet decided whether storage is worth it at all, read our solar panels with a battery vs without comparison first.
Where should the battery go?
Location affects safety and lifespan. In the UK, BSI’s PAS 63100:2024 says home batteries should not be installed in voids, roof spaces or lofts (Professional Electrician). That’s a UK specification, but the reasons it gives, poor ventilation and flammable insulation, apply anywhere. Ask your installer where they propose to fit it, why, and what the manufacturer’s instructions require. The electrical work must be done by a Registered Electrical Contractor (CRU).
Grants and VAT for solar battery storage
- SEAI grant: €600 flat for 5kWh or more, on top of up to €1,800 for panels (SEAI). Homes with existing PV can apply for the battery separately. SEAI’s guide says a battery-only application where PV isn’t already installed doesn’t need a post-works BER.
- Enhanced grant: up to €9,000 for panels and a battery for qualifying welfare households; see our free solar panels guide.
- VAT: 0% when installed with panels; 23% for a standalone battery installation (SEAI).
- Businesses: batteries are not eligible under SEAI’s Non-Domestic Microgen grant (SEAI).
FAQs
What is the best battery chemistry for home solar?
LFP is generally considered more thermally stable and longer-lived than NMC, according to industry sources. NMC is lighter and more compact. Ask for the chemistry and datasheet for any battery you’re quoted.
How long do solar batteries last?
Warranties of 10 years are typical, with some at 12 or 15. Real life depends on chemistry, cycles and temperature. Check the end-of-warranty capacity and throughput limit.
Is a 5kWh battery big enough?
It meets the SEAI grant minimum and may cover a typical evening for a smaller household. Check your evening usage before going bigger. Our post on solar panels with a battery vs without covers the payback side.
Can I add a battery to my existing solar panels?
Usually, if your inverter supports it or you add a battery inverter. You can apply for the €600 grant separately, but a standalone battery installation is at 23% VAT.
Does a solar battery work in a power cut?
Not automatically. Backup operation depends on the inverter, battery and wiring set-up, and may need extra equipment. Ask your installer to confirm in writing whether the system you’re quoted will supply power during an outage.
Get your solar quote today
Get your solar quote today. Tell us about your solar system and your evening usage, and we’ll connect you with SEAI-registered installers who can quote batteries side by side. Call 089 450 4544 with any questions.
