Home batteries · August 2026

The blackout test: 21 home batteries judged on one question.

A battery can score well overall and still leave a buyer with an unclear answer to the question that matters during an outage: what stays on, how quickly does it transfer, and can it start a demanding load? This article records the 21-system dataset snapshot published on 19 July 2026. It is not the current fleet table.

The split

Resilience is not the same as a general battery score.

The top of the table is defined by complete system behaviour, not capacity alone. Powerwall 3 combines grid-forming backup, a documented sub-20 ms transfer and motor-start evidence. Sigenergy SigenStor follows with a true UPS topology, while FranklinWH aPower 2 reaches third on the strength of its published motor-start capability and backup-power depth. At the other end, missing or slow transfer evidence materially changes the answer even where the overall battery score remains respectable.

review.solar

Blackout-protection score · 21 current battery records

The fleet spreads across a 38.6-point resilience range

Powerwall 391.6

fleet leader

SigenStor85.9

true UPS

Fleet median72.8

middle record

Battery-Box HVL53.0

evidence gap

Chart data

Series	Value	Note
Powerwall 3	91.6	fleet leader
SigenStor	85.9	true UPS
Fleet median	72.8	middle record
Battery-Box HVL	53.0	evidence gap

What moves the result

The hand-over moment matters as much as stored energy.

Three different claims are easy to blur together in a brochure. Grid-forming means the system can establish an AC reference in an outage. Whole-home seamless backup describes an integrated or validated setup able to carry the home through a fast transfer. Paired hybrid backup can be entirely appropriate, but the outcome depends on the inverter, gateway and installation design around the battery. None of these labels promises that every appliance on a particular property will remain powered: a buyer still needs an installer to size circuits, surge loads and switchgear.

Transfer evidence is the second divider. A true UPS topology keeps the inverter on the load path and documents no transition event. A fast relay may preserve many loads but still has a measurable hand-over. A speed above 100 ms, or one that is not disclosed, is a materially different proposition for sensitive electronics. The rubric deliberately gives those differences more weight than a generic claim of “backup”.

The reference table

The 19 July battery snapshot, with later corrections shown.

The table is deliberately a dated reference rather than a shopping list. The current battery benchmark is the broader decision tool. Each product name opens its live scorecard, where later evidence corrections control.

Rank	System	Blackout score	Documented backup position	Transfer evidence
1	Tesla Powerwall 3	91.6	Grid-forming	<20 ms
2	Sigenergy SigenStor	85.9	Whole-home seamless	True UPS · 0 ms
3	FranklinWH aPower 2	83.2	Paired hybrid	Not published
4	Enphase IQ Battery 5P	80.6	Grid-forming	<20 ms
Corrected	EcoFlow Ocean 2	Withdrawn	Not established	Not published
Corrected	EcoFlow Ocean 2 Plus	Withdrawn	Not established	Not published
7	GoodWe ESA All-in-One	78.3	Whole-home seamless	<5 ms
8	FoxESS PowerQ All-in-One	77.5	Whole-home seamless	<20 ms
9	BYD Battery-Box Premium HVS	75.5	Paired hybrid	<20 ms
=10	GoodWe Lynx Home F G2	72.8	Paired hybrid	<20 ms
=10	Sungrow SBH	72.8	Paired hybrid	<20 ms
12	LG Energy Solution enblock E15.5	72.2	Paired hybrid	Not published
13	AlphaESS Smile G3 S5	71.1	Paired hybrid	<20 ms
14	Anker SOLIX X1	67.8	Paired hybrid	<20 ms
15	FoxESS ECS CQ7	67.2	Paired hybrid	<20 ms
16	AlphaESS Smile G3 S5 BAT-9.3S	64.6	Configuration dependent	Not published
17	Redback Smart Hybrid System	62.8	Whole-home seamless	<100 ms
18	SolarEdge Home Battery	61.5	Paired hybrid	>100 ms or undisclosed
Corrected	sonnenBatterie 10/11	Withdrawn	Not established	Not published
20	Huawei LUNA2000 S1	60.5	Paired hybrid	>100 ms or undisclosed
21	BYD Battery-Box Premium HVL	53.0	Configuration dependent	Not published

A blank or unpublished transfer-speed claim is not treated as proof of a slow transfer. Corrected rows remain visible so the publication history is auditable; their earlier score and capability labels must not be used.

The buyer question

Ask for the outage design, not just the battery name.

Before choosing a system, ask the installer which circuits remain live, whether the design is whole-home or essential-load only, how the battery behaves when starting a pump or air-conditioner, what happens to rooftop solar while islanded, and whether a gateway is required. The answer should name the exact inverter, gateway and switchboard design. A battery specification alone is not the outage plan.

The same principle applies to warranty comparison. A strong blackout system is not automatically the strongest general battery proposition; use the battery warranty guide alongside the full scorecard before making a decision.

Sourcesbenchmark snapshot and product evidence

• Solar Analytica blackout-protection methodology, v1.0.0: backup coverage, transfer continuity, motor-start or surge evidence, and continuous backup power. This is a standalone sub-score and never changes an overall battery rating.
• review.solar generated product dataset, 21 battery records, snapshot 19 July 2026. Each table row links to its scorecard, which carries its model-specific source links, configuration notes and evidence status.
• Evidence correction, 23 August 2026: EcoFlow OCEAN 2, EcoFlow OCEAN 2 Plus and sonnenBatterie 10/11 snapshot rows withdrawn after exact-product re-audit.
• Method caveat: the score is a comparative publication tool, not electrical design advice. Actual backup performance depends on the installed inverter, gateway, circuits, load profile and local electrical requirements.