Which home battery should you shortlist?
Start with the job it needs to do. Powerwall 3 suits a comparison for substantial storage and higher output, where the network operator approves it. A single UK Enphase IQ Battery 5P is a smaller AC-coupled starting point. Fox ESS EP12 Plus is worth comparing when the installer proposes a compatible hybrid inverter.
| Battery | Stored energy | Continuous output | Backup equipment |
|---|---|---|---|
| Tesla Powerwall 3 | 13.5 kWh usable AC | 3.68 to 11.04 kW nominal AC at 230 V; above 3.68 kW on a single-phase supply needs G99 approval | Backup Gateway 2 [1] [8] |
| Enphase IQ Battery 5P, UK 1P | 5.0 kWh usable, maker stated; includes Enphase's reserves, so about 4.75 kWh reaches loads (our calculation) | 3.2 kVA apparent power | IQ System Controller 3 INT [2] [9] |
| Fox ESS EP12 Plus | 11.52 kWh nominal; approx. 10.37 kWh calculated DC window | AC power depends on compatible inverter | Inverter and switching design must be specified [3] |
These are three documented options, not the whole UK market. We have not tested them in homes, measured service response or proved a cheapest installed system. For an MCS installation, check the installer is certified for battery storage. Current MCS rules exempt battery products from the product-directory requirement; equipment conformity and a suitable installation design still matter. [7]
How did we compare home battery storage?
This desk comparison uses UK datasheets and the applicable territory-specific warranty documents. We compare stored energy, continuous power, short-duration load limits, efficiency measurement paths, backup equipment, cover limits and price evidence. There is no composite score or single winner.
Our smaller-storage choice follows the listed usable capacity, not physical wall area. Our higher-output choice follows the documented configured AC output, not an assumption that every house gets the maximum. Our hybrid-system choice depends on an installer's confirmed compatibility. We do not assign a best-value label without comparable complete installed quotes.
Newer variants can change the answer. The Enphase figures here are for IQBATTERY-5P-1P-INT, not a US model or the FlexPhase version. The warranty document must match your exact SKU, territory and activation date. We do not assign numeric warranty terms to Fox EP12 Plus from a policy that names only the broader EP12 family.
When is Tesla Powerwall 3 worth considering?
For larger storage and a higher-output backup proposal
Powerwall 3 provides 13.5 kWh of usable AC energy. Its UK datasheet gives configured output settings from 3.68 to 11.04 kW at 230 V, with continuous charging up to 5 kW for a single Powerwall 3 without Expansion units. The installer must specify the output approved for your site. On a single-phase supply, any setting above 3.68 kW (16 A), counted together with any other generation at the property, needs the network operator's agreement under G99 before installation (G99/NI in Northern Ireland). If the approval is 3.68 kW, Powerwall 3's output edge over one Enphase IQ Battery 5P (3.2 kVA) is small. [1] [8]
Powerwall 3 also contains its own solar inverter, rated for up to 20 kW of panels at standard test conditions across three MPPTs, and Tesla's sheet shows layouts that keep existing AC solar using a Tesla Remote Meter. [1]
Backup requires Tesla's Backup Gateway 2 in the UK configuration we checked. A battery-only price without a gateway is not a like-for-like backup-system price. The advertised 185 A LRA figure concerns starting a motor; it is not continuous output and cannot be compared with another battery's kW rating. [1]
Ask whether your evening demand can use its capacity regularly and which circuits remain powered in an outage. Choosing a large unit for occasional power cuts is a resilience decision; it should not be presented as certain bill-saving payback.
When is the Enphase IQ Battery 5P a better fit?
For a smaller starting capacity with AC coupling
One UK IQ Battery 5P has a maker-stated usable capacity of 5.0 kWh and 3.2 kVA continuous apparent power. Enphase's usable capacity technical note says that figure includes a 2 per cent outage reserve and a 3 per cent reserve for the battery's electronics, so the battery stops supplying loads at 5 per cent charge: about 4.75 kWh, our calculation. In backup systems with third-party PV inverters Enphase sets the stop point at 10 per cent, about 4.5 kWh. [2] [9] The UK sheet lists compatibility with third-party PV string inverters as well as Enphase solar microinverters. You do not need to replace functioning panels merely to choose it. [2]
kVA describes apparent power; the useful kW depends on power factor. Ask for the continuous kW available in the proposed system. Its UK sheet lists peak current during backup operation of 27.8 A for three seconds and 22.3 A for ten seconds; that is not a sustained output rating. [2]
Backup needs an IQ System Controller 3 INT. Grid-tied operation also needs the specified gateway and communications equipment. Price the complete configuration. Two batteries double the maker-stated usable capacity to 10 kWh (our arithmetic), but their combined rated output of 27.8 A is above the 16 A per phase G98 limit, so the network operator's agreement under G99 is needed before installation (G99/NI in Northern Ireland). [2] [8]
When does Fox ESS EP12 Plus make sense?
Compare the EP12 Plus when your quote already includes a compatible Fox hybrid inverter (the sheet lists Fox's own H1, KH, H3, H3-Pro and US series) and you want a larger battery pack. It lists 11.52 kWh nominal energy and 90 per cent depth of discharge. The sheet does not publish usable energy separately. [3]
Multiplying those figures gives 11.52 x 0.90 = 10.368 kWh, approximately 10.37 kWh. That is our calculated DC capacity window, before system conversion losses. It should not be treated as equivalent to Tesla's guaranteed beginning-of-life AC figure. [3] [1]
The Fox sheet lists a maximum charge and discharge current of 30 A, which it says varies with temperature, cell voltage and state of charge. That is a battery-side current, not household AC kW. Ask for the exact inverter model, its charge and discharge limits and the equipment needed for backup. Do not accept a backup promise based only on the battery name. [3]
Get the warranty for the supplied Plus variant attached to the quote. Ask for the retained-capacity floor and any cycling or throughput limit, including whether that limit also ends cover for defects. We do not infer those terms from another model-family policy.
Which battery has the strongest warranty?
Years alone do not answer that. Compare the retained-capacity floor, the cycles or energy-throughput limit and the equipment actually covered. A warranty threshold is a contractual minimum under conditions, not a prediction of the capacity your unit will have.
| Battery | Term and capacity floor | Conditions that change the comparison |
|---|---|---|
| Tesla Powerwall 3 | 10 years; 80% of 13.5 kWh at year 10 | UK: unlimited cycles for listed self-consumption, time-based control and backup uses; other uses capped at 37.8 MWh. [4] |
| Enphase IQ Battery 5P, UK 1P | GB: up to 15 years or 6,000 discharged cycles, whichever first; 70% at year 10 / 60% at year 15, of nameplate energy | England, Scotland and Wales; activation by Energize by date; authorised European-region supply. Exact covered SKU 1P-INT. [5] |
| Fox ESS EP12 Plus | Not rated: get the policy for the supplied Plus variant | Do not substitute a family warranty for the exact battery and purchase date. |
Tesla says Powerwall must be reliably connected to the internet to secure the full ten-year warranty; if it is offline for an extended period or not registered, Tesla may not honour the full ten years but will honour at least four years from installation. Enphase requires continuous connectivity, allowing interruptions outside the owner's reasonable control, and activation by the battery's Energize by date. Claims must be made within 90 days of discovering the defect and while the warranty runs. Its listed gateway, current transformers and communications kit have five-year cover. [4] [5]
Ask who deals with faults, whether labour and replacement access are included and who you contact if the installer closes. We have not ranked manufacturer support: comparable first-hand response data is missing.
Ask for the warranty for your exact battery model attached to the quote, and compare the retained-capacity floor and any cycles or throughput limit, not just the years. Check, too, whether full cover depends on the battery staying connected to the internet, as it does for two of the three batteries here.
Haroon AliWriting about property & energy for 11 yearsCan you compare the efficiency percentages?
Only when they measure the same path under comparable conditions. Tesla lists 89 per cent for solar to battery to home or grid. Enphase lists 90 per cent AC round-trip efficiency. Fox lists at least 95 per cent round-trip efficiency for its pack. Enphase also lists 96 per cent DC round-trip efficiency, which shows how far an AC figure sits below a battery-side one; ranking those numbers directly would mix measurement boundaries. [1] [2] [3]
Ask the installer which losses the savings forecast includes: charging, discharging, the inverter and standby use. A high battery-pack percentage does not by itself establish a higher annual saving than an AC-coupled system.
How much do these home batteries cost?
Use complete installed prices for a buying decision. Hardware listings can leave out the inverter, controller, gateway, electrical work, delivery and commissioning. We do not have matched installed-price evidence for all three, so we cannot name a cheapest option.
Tesla's UK quote request page showed £5,000 for one Powerwall 3 without a gateway and £5,975 with a gateway. Both exclude VAT, delivery, installation and other costs and fees. The no-gateway option also requires a Tesla Remote Meter, not included. Tesla says the final price comes from a Certified Installer. These are equipment-price observations from 13 October, unchanged on 14 October 2026, not installed-price ranges. [6]
For installed prices, Octopus Energy, an energy supplier that also installs batteries, says on its battery-only installation page (read 14 October 2026) that its prices "at present" start at £7,999 for a 13.5 kWh Tesla Powerwall 3 and £3,947 for a battery it calls 5 kWh, which it fits as either a Fox EVO or an Enphase IQ Battery 5P, depending on what the customer chooses. These are one supplier's starting prices, and Octopus says battery installation is subject to network operator (DNO) approval. The post says Powerwall 3 keeps power running in a power cut but does not say whether backup equipment is included in these prices, or mention VAT, so check the current price. For the Fox ESS EP12 Plus we found no published installed price: it needs an installed quote. [10]
Request the same items on each quote: battery model and number of units, usable energy basis, inverter, backup switching and circuits, controller, electrical alterations, commissioning, warranty administration and total payable price. Use our home battery cost guide for the installed-cost benchmark, keeping nominal and usable kWh separate.
A smaller suitable battery can be a better purchase than a larger underused one, but prove that with your forecast. Compare the system price and annual saving with the same household use and tariff assumptions. Tariff eligibility and export payments can change the result.
Will a home battery keep the house running in a power cut?
Only if the proposed installation includes a suitable backup arrangement. Ask which circuits are backed up, their total and starting loads, the reserve setting and how the battery recharges during an outage. Storage size alone cannot answer those questions.
A hypothetical battery with 5 kWh available supplying a steady 1 kW load has five hours of energy before losses and any reserve. That is our simplified calculation, not an operating-time promise for any product here. A high-power cooker can encounter an output limit even while the battery still has energy left.
Obtain a written backup design and a commissioning demonstration. An inverter's EPS label is not enough to establish which appliances in your home will keep running.
What is the best solar battery to buy in the UK?
The best fit depends on how much electricity you can move into cheaper hours, your evening demand, compatible equipment and any backup requirement. Start with whether a battery is worth it, then what size battery you need. Select a product after that.
What are the best solar panels with battery storage?
Compare the panels and battery as separate choices within one compatible system. Panel roof fit and forecast output matter; the battery adds storage, power and control requirements. Our solar panel comparison covers the panel decision.
What are the alternatives to Tesla Powerwall?
The Enphase system and a Fox battery with a compatible inverter are different configurations, not direct substitutes at the same price. Get comparable quotes with equal usable-energy needs and the same backup brief. We have not reviewed every UK alternative.
Can I add a battery to existing panels?
Yes, compatible AC-coupled configurations exist; the Enphase UK sheet expressly lists third-party PV string inverters. The battery's rated output counts with your existing inverter's towards the 16 A per phase G98 limit (3.68 kW on a single-phase supply); above that, the network operator's agreement under G99 is needed before installation (G99/NI in Northern Ireland). Check the proposed equipment and your existing tariff arrangements with the installer. Our adding a battery guide covers the retrofit task. [2] [8]
Sources
- Tesla, Powerwall 3 UK datasheet, 2026 UK edition; read 14 October 2026.
- Enphase, IQ Battery 5P UK datasheet, DSH-00857-1.0, 18 July 2025; IQBATTERY-5P-1P-INT; read 14 October 2026.
- Fox ESS UK, EP12 Plus datasheet, V1.0, 19 September 2025, battery warming UK sheet; select Datasheets/Batteries; read 14 October 2026.
- Tesla, Powerwall warranty, European warranty region, Rev 1.16, effective 3 December 2025; UK table; read 14 October 2026.
- Enphase, Warranty for storage systems, United Kingdom (England, Scotland and Wales), effective 15 September 2025. The file name mentions FlexPhase; its covered products schedule also lists IQBATTERY-5P-1P-INT; read 14 October 2026.
- Tesla, UK Powerwall quote request page, equipment prices seen 13 October 2026 and unchanged; read 14 October 2026.
- MCS, Installer Operating Requirements, Issue 2.0, 8 September 2026, section 2.2; read 14 October 2026.
- ENA, Engineering Recommendation G98, Issue 1 Amendment 7, section 2.8; read 14 October 2026.
- Enphase, IQ Battery usable capacity technical note, TEN-00026-2.0, November 2024; read 14 October 2026.
- Octopus Energy, Introducing battery-only installation with Octopus (supplier blog post), published 6 June 2025 and since updated; battery prices given as "at present"; read 14 October 2026.