Aiko Neostar 3S vs LONGi Hi-MO X10: Back-Contact Flagships Compared

For most of the last decade, picking a premium solar panel meant choosing between different front-contact cell designs — PERC, then TOPCon, with a heterojunction option at the top of the price list. In 2026 the premium end of the UK market has shifted decisively to back-contact cells, and two panels define it: Aiko's Neostar 3S+ 530W and LONGi's Hi-MO X10 540W. I've spent the past few weeks comparing these two for a real system spec, and the differences that matter are not the ones the spec-sheet headlines suggest.

Both panels move every electrical contact to the rear of the cell, so the front face is an unbroken dark surface with no busbars shading the silicon. Both hit 23.9% module efficiency. Both lose just 0.26% of output per degree above 25°C, and both are warranted to degrade no more than 0.35% a year. On paper they are nearly twins. In the details — construction, warranty, price and availability — they diverge sharply.

At a glance: the two panels

Aiko Neostar 3S+ 530W (model AIKO-A530-MCE60Db) is the third generation of Aiko's ABC — All Back Contact — technology. It is a 60-cell, dual-glass, all-black bifacial panel measuring 1954×1134×30mm and weighing 27.1kg. Aiko rates it at 530W from the front face alone, rising to 557W with 5% rear-side gain from reflected light.

LONGi Hi-MO X10 540W (model LR7-60HVH-540M) uses LONGi's HPBC 2.0 — Hybrid Passivated Back Contact — cells built on its TaiRay N-type wafer. It is also a 60-cell panel, at 1990×1134×30mm and just over 25kg, but with conventional single-glass construction (3.2mm tempered glass over a white backsheet) and a black frame rather than a full all-black face.

Both are physically bigger than the 54-cell, 1722–1762mm panels most UK installers quote by default. That is the point: around 530–540W per roof fixing instead of 440–465W. You can see the two side by side with full scoring on our interactive comparison page.

ABC vs HPBC 2.0: does the cell technology matter?

Functionally, far less than the marketing suggests. Both approaches solve the same problem — front-side busbars reflect light and cost efficiency — by moving the contact grid to the back. Aiko's ABC design eliminates front metallisation entirely. LONGi's HPBC 2.0 is a hybrid passivated design that reaches essentially the same place by a different route. The measurable outcomes are what count, and here they tie: 23.9% module efficiency for both, a −0.26%/°C temperature coefficient for both, and a maximum 0.35% annual degradation for both.

Back-contact cells also shade more gracefully than conventional panels. With no front busbars, partial shading tends to cost output more proportionally rather than knocking out whole cell strings — useful on UK roofs with chimneys and dormers, though a well-designed string layout still matters more than cell architecture.

Construction and warranty: Aiko's clearest win

The Neostar 3S+ is a dual-glass panel; the Hi-MO X10 540W is not. Aiko laminates the cells between two sheets of 2.0mm tempered glass, which protects the cells from moisture ingress and mechanical stress from both sides. LONGi uses a single 3.2mm front glass over a polymer backsheet — a proven construction, but one with a shorter track record at the 30-year timescales these panels are warranted for.

The warranty gap follows directly. Aiko backs the Neostar 3S+ with a 25-year product warranty alongside its 30-year performance warranty, guaranteeing at least 88.85% of rated output in year 30. LONGi offers the same 30-year performance cover (at least 88% in year 30) but only a 15-year product warranty — the part that pays out if the panel physically fails. Fifteen years is respectable; it is also a full decade less than Aiko, REC and other premium rivals now offer, and product failure is precisely the risk you are paying a flagship premium to avoid.

Price and availability in the UK

At the time of writing, the Aiko is meaningfully cheaper per panel. UK distributor stock of the Neostar 3S+ 530W is selling at around £129 per panel including VAT, while the Hi-MO X10 540W — still thin on the ground with UK stockists — is listed at around £167. Per watt, that is roughly 24p against 31p. Supply-only prices bounce around as stock lands, so treat both as a snapshot rather than a fixed gap, but right now you are paying more for the LONGi and getting 10W and a slightly lighter panel in return.

Context matters here: a one-generation-older 445–465W TOPCon panel costs £60–£100. On an unshaded roof with no space constraint, cheaper TOPCon still wins on pure £ per kWh — see our best solar panels guide for how the whole market stacks up. These flagships earn their premium when roof space is tight, when you want maximum output from a fixed number of fixings, or when the 25–30 year warranty maths drives the decision.

Brand strength and bankability

LONGi is one of the world's largest solar manufacturers, with the wafer production, global service network and installer familiarity that comes with that scale. Aiko is a major cell manufacturer that moved into modules more recently; it is well established in the UK residential market and its warranty terms are insurance-backed, but LONGi's sheer scale is the stronger bankability story if you weight the odds of the company existing in year 25 of a warranty claim. Our guide to solar panel manufacturers covers how to read Tier 1 lists and why they measure bankability, not quality.

Fitting either panel: check your roof first

Both panels are large-format, and that has practical consequences. At 1954mm and 1990mm long respectively, they need roughly 230–270mm more roof length per portrait course than a standard 54-cell panel, and at 25–27kg they are heavier to handle and load onto rails. Confirm your installer's mounting system is specified for the panel dimensions, and re-run the layout maths before assuming a like-for-like swap from a 440W quote — our guide to how many panels you need explains the sizing trade-offs. A 10-panel array of either panel reaches 5.3–5.4kWp, which on a single-phase supply will usually mean your installer applies for G99 approval or caps the inverter — worth raising at quote stage.

Verdict: which should you buy?

For most UK buyers choosing between exactly these two panels today, the Aiko Neostar 3S+ is the stronger buy. Same efficiency, same temperature behaviour, same degradation rate — but dual-glass construction, a 25-year rather than 15-year product warranty, bifacial capability, and a lower UK price. The LONGi Hi-MO X10 takes it if the extra 10W per panel genuinely changes your system total, if your installer gets better LONGi trade pricing than retail listings suggest, or if manufacturer scale is your deciding factor. Both are excellent panels; neither is a mistake. See the full spec-by-spec scoring on the comparison page, or read the individual reviews for the Neostar 3S+ 530W and Hi-MO X10 540W.