A single 2030 number would be a guess

A capital allocator planning a 2028 procurement contract, a 2030 site-design assumption, or a multi-year hedging position against module ASP does not need one confident number. They need to know the range the credible sources span, and why. Four organisations publish the roadmap data this model draws on, ITRPV (VDMA's International Technology Roadmap for Photovoltaics), CPIA (China's national industry association), Exawatt and NREL, and on the metrics this model is built around, they disagree by wide margins. On back-contact cell share by 2030 alone, published estimates range from 15 to 35 per cent: more than double, from source to source, on the same calendar year.

The range reflects genuinely different reads on the same transition. Shipment-data trackers, capacity-announcement trackers and lab-record trackers each watch a different leading indicator, and each is right about what it measures. This report keeps the disagreement explicit as three named scenarios, with a planning read for each.

Three scenarios, seven metrics

Seven metrics carry the planning weight. Each scenario endpoint below is sourced to a specific roadmap position; none is a split difference.

Full eleven-metric table, including n-type wafer share and wafer-thickness endpoints, and the complete anchor-by-anchor sourcing: review.solar/roadmap.

Near-term procurement, 2026-2027

For contracts and specifications locking in within the next two years, TOPCon is simply the market consensus: it holds 65 per cent of 2025 shipments in this model's baseline, and every scenario, including the low case, keeps it above 50 per cent through the rest of the decade. It is the only architecture in the model with that property, which makes it the sourcing default with the least scenario risk on these numbers.

Committed and built back-contact capacity from LONGi and Aiko Solar alone already exceeds 100 GW on the companies' own announcements, running ahead of the more conservative roadmap trajectories, which is why this model's base case of 23 per cent sits at the upper end of what a cautious planner might have assumed even twelve months ago. That schedule puts supplier qualification in the 2026-2027 window.

HJT carries the highest revision risk in the model, and the instability is in its roadmap rather than its physics: CPIA's China roadmap cut its 2030 HJT forecast from 20 to 7.5 per cent within about a year, tracking a continued shift of investment toward back-contact and tandem at several major cell makers. A specification or supply agreement built on rapid HJT scale-up should be rechecked against the latest roadmap vintage before it is finalised.

Mid-decade capacity and budget planning, 2028-2030

For site-design and land-yield assumptions running to 2030, the efficiency band (24.0 to 26.0 per cent weighted average) and utility flagship power band (750-900 Wp) bracket the reasonable range for capacity-per-hectare modelling; using the high end of either band as a base-case planning assumption understates land or roof-area requirements if the base case, not the high case, is what ships. For budget and hedging models against module ASP, the US$0.06-0.10/Wp ex-tariff band has to be read together with the specific tariff regime a given jurisdiction applies: US landed prices in 2025-2026 ran materially above this global ex-tariff band because of AD/CVD duties, and any procurement model that ignores jurisdiction-specific trade policy will misprice the delivered cost regardless of which global scenario proves correct.

Every scenario, including the high case, keeps commercial tandem share under 5 per cent through 2030, even though lab efficiency records (above 34 per cent by 2026) are running well ahead of most roadmaps' expectations for the early 2030s. A capital plan that assumes near-term tandem availability at scale is planning against the lab record, not the factory schedule.

The roadmaps themselves keep moving

The roadmaps themselves keep moving, and that matters as much as any individual endpoint. N-type mono-Si wafer share stood at a reported 70 per cent for 2024; ITRPV's 17th edition (2026) put the 2025 figure at approximately 82 per cent, a twelve-point jump inside twelve months, ahead of most 2024-vintage roadmaps' full multi-year path to that level. CPIA revised its own HJT forecast down by more than half in about a year. ITRPV revised its own back-contact long-run share upward in its most recent edition. An industry mid-transition moves faster than annual publication cycles can capture.

The revisions also run one way. The n-type jump, the back-contact upgrade and the 100-plus gigawatts already committed at LONGi and Aiko all landed ahead of the conservative trajectories, and the one downward revision, HJT, tracks the same shift of investment toward back-contact and tandem. On this record, the planning error to guard against is undershooting the transition. Contingency planning should lean on the high side of the technology-shift bands, and any multi-year commitment built on a single-point 2030 assumption needs a revisit clause against the current roadmap vintage, at least annually.

Three scope limits

Three scope limits matter for anyone applying these numbers directly. The ASP band is a global ex-tariff figure: it excludes region-specific trade-barrier premiums, which in 2025-2026 nearly tripled effective landed cost in some jurisdictions relative to the ex-China baseline. The tandem scenario band bounds commercial shipment share only: it says nothing about when, or whether, a specific supplier's tandem product will be bankable at the volume a given project needs. And this model tracks published third-party roadmaps (ITRPV, CPIA, Exawatt, NREL) rather than generating an independent proprietary forecast: every number here traces to a named source, and where sources disagree, the disagreement is preserved as the scenario spread.