Methodology

How a score is built

Each product is scored against a published rubric of weighted pillars. Each pillar contains criteria. Each criterion maps a measured specification to a band (0–100 pts). Pillar scores are weighted averages of their criteria. The overall score is a weighted average of pillar scores. The same arithmetic runs on every product. No editorial adjustments.

What happens when a spec is missing

Every criterion declares a missing mode. Floor (40 pts): the manufacturer did not disclose this figure. Non-disclosure is penalised. Neutral (50 pts): this axis is not universally published in this product class. Absence is not penalised but nothing is assumed. Exclude: the criterion is dropped and the remaining pillar weights renormalised. Used for data not yet collected, or for axes that genuinely do not apply to a product.

Classes, not one leaderboard

Products are sorted into market classes (e.g., Premium European, Performance & Value) and judged within those classes. A boutique premium product should not be ranked against a volume residential product on scale, and vice versa. The class system prevents misleading cross-segment comparisons while still publishing all scores.

International publication

review.solar is an international publication. The root international safety standards (IEC 62109 for inverters; IEC 62619 for batteries; IEC 61215/61730 for panels) are the primary certification reference. National grid-connection overlays (AU AS/NZS 4777.2 + CEC; US UL 1741; EU VDE) are market-specific layers applied by regional distributors at installation. A product certified to the international base standard is not penalised for the absence of a regional national listing.

Evidence and market context

Every audit-sheet row is labelled as sourced, reviewed absence, estimated, derived, or not found. Reviewed absence means the linked exact-product material was checked but did not publish the qualifying detail. It is evidence of non-disclosure in the reviewed material, not proof that a capability can never exist. Not found is reserved for rows where no direct source has been located. An estimate or missing source is never presented as a verified fact. Product scorecards also state when their market review was last checked. A product marked market review not yet completed has no implied availability, certification, warranty or installer-compatibility claim for your location: confirm those points before purchase.

Why no product scores 100

The ceiling is anchored to the technological frontier, not the best current product: a hypothetical module, battery or inverter that is best-in-class on every criterion simultaneously. No real product achieves that, so even the market leader keeps visible headroom, and the top rating tiers stay reserved for genuine advances. The scale is a distance-to-frontier measure, which is why it rewards progress instead of declaring a winner "perfect".

Ageing technology: successor flags and the legacy tier

Technology moves. We mark that in two escalating steps, and neither ever changes a product's score. First, a successor flag: when a clear next-generation model exists in the same manufacturer series, the older model carries a sourced amber note linking to its successor. Its score is unchanged and it stays in active assessment: the flag simply tells you a newer generation exists. Second, the legacy tier: when a product is genuinely end-of-life, either because the manufacturer has attested it is retired or because we can source that it is no longer made or sold, it moves to a frozen legacy record. A legacy product keeps the exact score it held on its last active day, stamped with the rubric version and the date it was archived; it leaves active leaderboards and class-champion contention but stays visible and linkable for anyone still running that hardware. A frozen score is never recomputed against a later rubric and is never compared like-for-like against a currently-scored product. Manufacturers may attest that their own product is retired, and we may reverse a retirement we find inaccurate; a manufacturer can influence whether their product is listed as current or retired, but never its score, and never any product's rank. Retiring a product is proven not to change any other product's score or rating.

What the score represents

Every score is tied to a named model or configuration. For panels, thin-film modules and inverters, the benchmark uses the highest published output only inside one physical, electrical and market-certification series; a lower model stays visibly in research until the maximum model's variant-sensitive evidence has been checked. Batteries instead show the supported capacity range and retain a named reference configuration, because a larger stack is not inherently a better battery. Plug-in ESS records score one exact model and publish grid-injection, backup and storage metrics separately. Regional ranges are kept distinct from the global family so an Australian maximum is never silently presented as a worldwide one.

External data sources

Scores draw on: manufacturer datasheets and warranty documents (primary sources, archived copies hosted under /sources/); IEC standards (61215, 61730, 61701, 62716, 62109, 62619, TS 62804); UL 9540A and UL 1741; AS/NZS 4777.2; independent test programmes: PVEL PV Module Reliability Scorecard, RETC, DNV battery scorecard, HTW Berlin Stromspeicher-Inspektion (RSP/SPI), ITP Renewables; BNEF Tier-1 lists (displayed, never scored); and peer-reviewed literature cited in individual rubric changelogs. What each of those third-party sources actually establishes, and which decision it answers, is set out in Three names on a spec sheet.

Methodology change log

Every rubric change is versioned and dated. Expand a rubric for its full history.

Cell balancing: active vs passive

Passive balancing dissipates excess charge as heat through resistors. Active balancing moves charge between cells or modules instead of simply dissipating it. The distinction can matter over long service life, but it is often poorly disclosed. A module optimiser, pack-level control or generic BMS claim is not treated as proof of active cell-level balancing. Where exact architecture is not published, the audit row records a reviewed absence and the rubric's non-disclosure band applies.

Warranty degradation guarantee: the clause most consumers never read

An end-point-only warranty (e.g., "≥70% capacity at year 10") permits a battery to lose 25% of its capacity in year two and then stabilise. The manufacturer satisfies the warranty but the customer suffers large early losses during the years of heaviest use. A stepped guarantee adds a midterm checkpoint. A linear annual-cap guarantee limits degradation per year and prevents front-loaded decline. Only Sonnen currently offers a linear degradation guarantee in this product set. Tesla offers stepped midterm + end-of-term. All others are end-point only.

Grid-forming vs grid-following

A grid-following battery needs an external AC voltage and frequency reference to operate. It cannot function without the grid or a running generator to synchronise to. A grid-forming battery creates that reference itself: it can black-start a home from a complete outage, run indefinitely from solar, and synchronise a generator or additional solar to its own microgrid. Sonnen, Tesla Powerwall 3, and Enphase IQ Battery (with IQ System Controller) are grid-forming in this product set. Most modular batteries (BYD, LG, Sungrow SBH, Huawei Luna, LG RESU) are grid-following. Their backup capability depends entirely on the paired hybrid inverter.

Gateway disclosure: not a penalty

Some batteries require a separate gateway or hub for full smart functionality (VPP dispatch, load management, blackout protection). Where this applies, the scorecard shows an amber gateway note. Gateway dependency is not penalised in the score. A gateway mounted at the switchboard can be the correct topology when the battery is installed in a garage, shed, or any location remote from the main electrical panel. The gateway note is a disclosure so the consumer knows a separate box exists and understands its role.

Blackout protection: a standalone sub-score

Outage resilience is decision-critical for many battery buyers, but the capabilities that define it sit in three different pillars of the main rubric, so no single pillar score answered the question. Battery scorecards therefore carry a separate blackout-protection sub-score (0–100, shown with the product's rank and the fleet median). It re-weights sourced specs already scored in the main rubric around that one question: backup coverage tier, switchover continuity, surge/motor-start strength, backup power depth, and off-grid solar recharge. It is a standalone benchmark: it never feeds the overall product score, and the same missing-data rules apply (non-disclosure floors at 40; not-applicable criteria are excluded and re-normalised). The sub-rubric is published as blackout_rubric_v1 with its own change log.

Semiconductor technology: why it matters

Silicon carbide (SiC) and gallium nitride (GaN) switching devices achieve lower conduction and switching losses than standard silicon IGBT, the same transition that transformed EV drivetrains. SiC excels at high-voltage C&I applications (the Fronius Argeno 125 is the first confirmed SiC residential/C&I inverter in this product set, enabling its 99.1% peak efficiency). GaN excels at the low-voltage, high-frequency switching of microinverters (Enphase IQ8). Standard silicon IGBT is mature, field-proven, and cost-effective. The 55-pt band reflects that it is the established technology, not a failing one. Products using SiC or GaN earn a technology premium that reflects genuine long-run efficiency advantages, particularly at partial load, which is where solar inverters spend most of their operating life.

Night standby consumption: the silent lifetime cost

An inverter drawing 10W during 11 non-generating hours per night consumes approximately 400 kWh over a 10-year warranty term. That is energy the household pays for but never benefits from. Fanless residential inverters typically draw 1–3W; smart-fan products 3–6W; C&I products more, though at larger system scales the percentage impact is negligible. This criterion is scored as neutral missing mode. Many manufacturers do not publish standby wattage, and absence of data is not penalised. Products that publish this figure and achieve low standby earn a legitimate competitive advantage.

Reactive power range: voltage management on the real grid

Voltage rise at the end of distribution feeders is the primary physical constraint on solar penetration in most Australian networks. Reactive power injection (Q(U) volt-VAR response) is the tool networks use to manage it. The range of that response (±0.8 pf vs ±0.9 pf, and whether the inverter also supports Q(P) active-power-dependent response) determines how much the inverter can contribute to network stability. All AU CEC-approved inverters support Q(U) response to AS/NZS 4777.2 as a minimum; the differentiation is in whether Q(P) four-quadrant response is also implemented. Huawei SUN2000 is the only confirmed four-quadrant product in this set.