Chapter 8　What the same money could have bought

Key points

• Public support that can be confirmed as directed at perovskite solar has published ceilings of about 288 billion yen: 105.1 billion from the Green Innovation Fund, 171.2 billion across four GX Supply Chain awards, and 12 billion over two years of Ministry of the Environment deployment subsidies. All are award ceilings or budget lines, not grant decisions or actual outlaysC · CL-032
• At the 2023 construction cost used in the government's generation-cost review (176,000 yen/kW for utility-scale solar), the same 288 billion yen corresponds to about 1.6 GW of utility-scale solar if paid in full, or about 3.3 GW at the 50% subsidy rate of the GX Supply Chain programme. It corresponds to about 2.7 GWh of commercial and industrial battery storage (106,000 yen/kWh), or to about 58 MW of perovskite at the actual unit cost of the ministry's deployment subsidy (7.46 million yen/kW, two-thirds subsidised)C · CL-033
• If 20 GW is reached in 2040, the government's own cost gap (15.3 yen − 7.9 yen) applied to annual output of 24.5 TWh is about 180 billion yen a year. At the 14 yen self-sustaining level it is still about 150 billion yen a year; at 10 yen, about 50 billionC · CL-034
• The comparison shows what the same money would buy in silicon. It does not value what perovskite is meant for: sites where silicon cannot be installed. The comparison holds for the part of rooftop demand (95% of the estimate) where silicon could also be installedA · EV-074

1. The scale of public support

Public support for perovskite solar runs through several programmes, each with different layers: budget line, award ceiling, grant decision and actual outlay (see the public support register, Japanese). This chapter collects only "published ceilings that can be confirmed as directed at perovskite"C · CL-032.

Not included: the annual budget line of the GX Supply Chain programme (shared with water electrolysis and offshore wind), the cost of commissioned studies, municipal subsidies (Tokyo's 0.9 billion yen and others), tax relief, and ministry budgets from FY2027 onwards. IEEFA's "about 1 trillion yen over the next ten years" is the planned total for "next-generation renewables" as a whole, not for perovskite aloneA · EV-027.

Actual outlays, other than the research and development portion of the Green Innovation Fund, have not been published. Sekisui Chemical's first line (90 billion yen, operating from FY2027) is under way, and 157.25 billion yen is the ceiling through 2029A · EV-016. The 288 billion yen is therefore "what the government has committed as a ceiling", not "what has been spent".

2. Unit costs from government papers

The unit costs used for the comparison are 2023 actuals published by the government's own review bodies.

3. The substitution

Dividing about 288.4 billion yen by the unit costs above gives the followingC · CL-033.

Three cautions apply.

First, most of the public support (the Green Innovation Fund and the GX Supply Chain programme) goes to manufacturing plant and research, not to deployment. "288 billion yen builds 1.6 GW of solar" is a substitution in which the same money is redirected to the deployment side; the industrial goal of building a manufacturing base must be assessed separately.

Second, the unit costs come from different dates. Solar and storage are 2023 actuals; perovskite is a 2025 pilot figure (including ancillary costs) and a 2040 assumption. If the 2040 perovskite cost of 204,000 yen/kW materialises, the volume the same money buys is of the same order as 2023 utility-scale solar. But in that same 2040, the government's estimate assumes utility-scale equipment cost has fallen to 56,000 yen/kWA · EV-048.

Third, each amount is a ceiling, and actual spending may be lower.

4. The generation-cost gap in 2040

Taking the 2040 cross-section in which 20 GW has been reached, we apply the generation-cost review's figures to find the annual cost gapC · CL-034.

20 GW × 8,760 hours × 14% capacity factor ≈ 24.5 TWhA · EV-047. The gap is what customers or subsidies pay each year above the cost of obtaining the same electricity from silicon. On the government's estimate it is around 180 billion yen a year; even if the upper end of the self-sustaining level, 14 yen, is reached, it is 150 billion yen a year. The gap widens further if the perovskite lifetime is 10 years (Chapter 4: 24–25 yen).

5. Where the comparison does not hold

The substitution in this chapter has limits.

The policy purpose of perovskite is to open up sites where silicon cannot be installed: low load-bearing roofs, walls, windows. At those sites, the option of "installing silicon for the same money" does not exist. The comparison is meaningful for the part of deployment where perovskite goes onto sites that could also take silicon.

In Mitsubishi Research Institute's reproduction of the strategy's demand estimate, rooftops account for 20.1 GW (95%) of the 20 GW in 2040. Neither the strategy nor the commissioned study publishes the share of roofs that cannot bear the loadA · EV-074. "How much of the 20 GW could be replaced by silicon" therefore cannot be fixed, and the gaps in this chapter are upper-bound indications.

Nor can the substitution measure the industrial goal (a GW-class domestic manufacturing base) or sales in overseas markets. We will assess these when the overseas record (Chapter 7) and the cost-effectiveness analyses requested under disclosure (Chapter 10) are in.

6. What we know so far, and what we do not

What we know

• Public support confirmable as directed at perovskite has published ceilings of about 288 billion yen; actual outlays are unpublished
• At 2023 unit costs, the same sum corresponds to 1.6–3.3 GW of utility-scale solar or 2.7–5.4 GWh of commercial and industrial storage
• At the ministry subsidy's actual unit cost it corresponds to about 58 MW, a little over half the 100 MW target for government buildings (Chapter 5)
• Even if 20 GW is reached in 2040, the government's estimate leaves a cost gap of 150–180 billion yen a year
• The substitution holds only for sites that could also take silicon, and that share is unpublished

What we do not know (being checked)

• Grant decisions and actual outlays under each programme (disclosure requests 05A–05C)
• Whether the government has produced any cost-effectiveness analysis (CO2 reduction, employment, cost) (disclosure request 04)
• The share of the 20 GW at sites where silicon cannot be installed

Sources

Amounts are in yen; unit costs in yen per kW or per kWh. All calculations are our own, made mechanically from published figures, and are graded C. URLs and retrieval dates for every document are in the evidence register and primary-source list (Japanese).

Pages in this series

• Series home
• Chapter 1 Where did 20 GW come from?
• Chapter 2 What the council discussed (Japanese)
• Chapter 3 Who decided, who received (Japanese)
• Chapter 4 Comparing generation costs
• Chapter 5 Demand created by subsidies (Japanese)
• Chapter 6 How the press reported it (Japanese)
• Chapter 7 What is happening abroad
• Chapter 8 What the same money could have bought
• Chapter 9 Open questions to the government (Japanese)
• Policy timeline (Japanese)
• Public support register (Japanese)
• Evidence register and primary sources (Japanese; CSV)

Related pages

• Rethinking perovskite solar from zero (Japanese) — Checking the technical, economic and institutional premises one by one.
• Reviewing MRI's perovskite industrial-policy column (Japanese) — The 'Team Japan' argument against primary sources.
• JC-STAR and grid cyber-resilience: an effectiveness check — An earlier I-S3 investigation using the same evidence-register method.

Citation and reuse

The CSV and Markdown source files (index) are released under CC BY 4.0. You may copy, adapt and use them commercially if you credit I-S3 Co., Ltd. and link to this page. Quotations from the text with attribution are welcome.

Anyone named in this series who wishes to rebut or correct a statement may write to our contact form or s_masuda@i-s3.com; we publish rebuttals at equal length.

Suggested citation

Masuda, S. (2026). "Chapter 8　What the same money could have bought". I-S3 Co., Ltd., published 2026-10-29, https://www.i-s3.com/perovskite-policy-investigation-ch8-opportunity-cost-en.html