Let us put only published figures into the formula in the text. The subject is a high-voltage 2 MW / 8 MWh plant bidding into primary offline through an aggregator. The one question: using published figures alone, how many yen is the adder? The formula and what its words mean are in 50-2 Rules.
The answer first. Set in the Tokyo area, the adder is ¥1.411 in year 1 of operation, ¥0.959 in year 2, ¥0.809 in year 10 and ¥0.711 in year 17. When depreciation ends in year 18, the amount you may recover turns negative and the adder falls to the Type A ¥0.33. All figures are in ¥/ΔkW·30min (per promise to hold 1 kW open for 30 minutes).
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1. The figures we put in
We included only items with a published unit price. Items without one are not zero but blank. They are left as spaces for your own plant's figures.
| Item | Value used | Source and method |
|---|---|---|
| Construction cost | ¥68,000/kWh × 8,000 kWh = ¥544 million | METI, “Current status and issues of stationary storage systems” (12 March 2025, Document 6), p. 5. Battery ¥41,000, PCS ¥6,000, other ¥7,000, construction work ¥14,000 (analysis by Mitsubishi Research Institute; COLUMN 40) |
| Depreciation | Straight-line over 17 years: ¥32,096,000 a year | The Ministerial Ordinance on Useful Lives, Appended Table 2, gives 17 years for “electricity business equipment — other equipment — mainly made of metal”. The only basis for putting grid-scale batteries on this line is press reports (second-hand accounts of the National Tax Agency's view) |
| Repairs | ¥5,000/kW/year × 2,000 kW = ¥10 million a year | Agency for Natural Resources and Energy, 21 June 2023, Document 7 (battery parameters for the Long-term Decarbonization Power Source Auction) |
| Generator-side charge (kW portion) | Each TSO's unit price × 2,000 kW × 12 months. Tokyo: ¥100.12/kW·month, ¥2,402,880 a year | Each general transmission and distribution operator. Five of them raise their unit prices on 1 November 2026, so the new prices are used. Batteries are exempt from the kWh portion |
| Fixed asset tax | Tax rate 1.4%. Assessed value is acquisition cost × 0.936 (first year), then × 0.873 each year. Zero in year 1 of operation. Tax rounded to the nearest yen | Local Tax Act, Article 350; Fixed Asset Valuation Standards, Appended Table 15 |
| Capacity market (deemed revenue) | 2,000 kW × adjustment coefficient 70.8% (from monthly averages before rounding; rounded to the nearest kW) = expected capacity 1,415 kW. × area price ¥15,111/kW = ¥21,382,065 a year. Deducted from year 2 | OCCTO: FY2029 adjustment coefficient table, Form 2, and main auction results |
| Wholesale-market revenue | 0 | See section 5 for why |
| Volume you can bid (expected bid volume) | 2,000 kW × 48 slots × 365 days × 90% = 31,536,000 ΔkW·30min | Our placeholder (90% allows for charge/discharge constraints) |
| Personnel costs | (your own figure) | No published unit price |
| Outsourcing (O&M) | (your own figure) | No published unit price |
| Insurance, land rent | (your own figure) | No published unit price. Whether they can be included is also unsettled |
| Aggregator costs (identified fixed costs) | (your own figure) | Identify from the contract breakdown |
Adding the blank items raises the adder by that much. With a divisor of 31,536,000, every ¥10 million a year of fixed costs adds about ¥0.32.
The items we did include also leave room in how they are set. Expected capacity in the capacity market is the 12-month average of “each month's adjustment coefficient × each month's dischargeable output”; taking dischargeable output as the 2,000 kW installed capacity is the upper end. We assumed the generator-side charge applies to the full 2,000 kW (with a contract for charging, the base becomes smaller). Fixed asset tax is not among the text's examples (unsettled), but it is a fixed cost by nature, and the Long-term Decarbonization Power Source Auction counts it in maintenance costs, so we included it. Taking it out lowers year 2 by ¥0.226.
2. The breakdown for year 2
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| Tokyo, base (¥) | Year 1 | Year 2 | Year 10 | Year 17 | Year 18 |
|---|---|---|---|---|---|
| Depreciation | 32,096,000 | 32,096,000 | 32,096,000 | 30,463,999 | 0 |
| Repairs | 10,000,000 | 10,000,000 | 10,000,000 | 10,000,000 | 10,000,000 |
| Fixed asset tax | 0 | 7,128,576 | 2,405,009 | 929,429 | 811,392 |
| Generator-side charge (kW portion) | 2,402,880 | 2,402,880 | 2,402,880 | 2,402,880 | 2,402,880 |
| Total fixed costs | 44,498,880 | 51,627,456 | 46,903,889 | 43,796,308 | 13,214,272 |
| Less capacity market (deemed) | 0 | −21,382,065 | −21,382,065 | −21,382,065 | −21,382,065 |
| Upper limit to recover | 44,498,880 | 30,245,391 | 25,521,824 | 22,414,243 | Negative |
| Volume you can bid (ΔkW·30min) | 31,536,000 | 31,536,000 | 31,536,000 | 31,536,000 | 31,536,000 |
| Adder (¥/ΔkW·30min) | 1.411 | 0.959 | 0.809 | 0.711 | 0.33 (Type A) |
In year 1 the capacity market is not deducted, so fixed costs of ¥44,498,880 are divided as they are, giving ¥1.411. In year 2 fixed asset tax is added, but ¥21,382,065 of deemed capacity-market revenue is deducted, so the adder falls to ¥0.959. After that it falls slowly, only as fast as fixed asset tax shrinks each year.
When depreciation ends in year 18, fixed costs become ¥13,214,272, less than deemed capacity-market revenue. The text says nothing about years in which the upper limit turns negative (unsettled). From the sentence “after the fixed costs for the current fiscal year have been recovered, the certain amount shall be that of a Type A resource”, we use ¥0.33 here. In years where the calculated value falls below ¥0.33, we also use ¥0.33.
3. The biggest step comes in the year deduction starts
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The biggest drop in 20 years comes in the year deemed capacity-market revenue starts to be deducted. In this estimate that is year 2, a fall of ¥0.452 from ¥1.411 to ¥0.959. It is larger than the step in year 18 when depreciation ends (¥0.381, from ¥0.711 to ¥0.33), and that held in every one of the nine areas.
The position of the step moves, though, with the year deduction starts. What the text exempts is “resources that, being newly in operation, could not bid into the capacity market in time”, and it does not say up to which year that applies (unsettled). If deduction starts later, the step moves back to that year.
4. Comparing the nine areas
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| Area | Year 1 | Year 2 | Year 10 | Year 17 | Year 18 |
|---|---|---|---|---|---|
| Hokkaido | 1.419 | 0.851 | 0.701 | 0.602 | 0.33 |
| Tohoku | 1.406 | 0.798 | 0.648 | 0.550 | 0.33 |
| Tokyo | 1.411 | 0.959 | 0.809 | 0.711 | 0.33 |
| Chubu | 1.408 | 0.985 | 0.835 | 0.736 | 0.33 |
| Hokuriku | 1.406 | 0.957 | 0.807 | 0.709 | 0.33 |
| Kansai | 1.423 | 1.000 | 0.850 | 0.751 | 0.33 |
| Chugoku | 1.400 | 0.948 | 0.798 | 0.699 | 0.33 |
| Shikoku | 1.419 | 0.965 | 0.815 | 0.716 | 0.33 |
| Kyushu | 1.410 | 0.868 | 0.718 | 0.619 | 0.33 |
In year 1 the adder is ¥1.400–1.423, and the only difference between areas is the unit price of the generator-side charge. From year 2 the gap widens, from ¥0.798 in Tohoku to ¥1.000 in Kansai. The larger the amount deducted as expected capacity × area price, the lower the adder — so Tohoku, Hokkaido and Kyushu come out lowest. Tokyo has a high area price, but its 4-hour adjustment coefficient, at 70.8%, is the lowest of the nine areas, so less is deducted.
5. What moves it, and how
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- Construction cost. At ±20%, year 1 moves to ¥1.207–1.615 and year 2 to ¥0.710–1.208. It is the input that matters most.
- Share you can bid. The smaller you take the divisor, the higher the adder. But the denominator is “the ΔkW that can be bid”, and lowering it by assuming few awards is not allowed.
- Adjustment coefficient. Setting the coefficient at 100% (the upper limit) gives ¥0.679 in year 2. That is ¥0.28 lower than the ¥0.959 from the published table — this much movement from how the coefficient is set alone.
We set wholesale-market revenue at zero. The text lists “wholesale-market revenue” as an example of revenue from other markets but does not say whether it means expected or actual revenue. Having assumed that 48 slots × 90% go to the balancing market, the plant cannot discharge on the wholesale market in those hours. Wholesale earnings enter the ceiling's first term as opportunity cost, so deducting them here too would count them twice. If you earn wholesale revenue in the remaining slots you do not bid, there is room to be asked to deduct that part (unsettled).
6. Falling to ¥0.33 partway through the year
The Type B adder applies only until the year's fixed costs are recovered. Once they are, it falls to the Type A ¥0.33, even partway through the year. When recovery counts as complete depends on how much of ΔkW revenue is counted towards it, and the text does not say (unsettled).
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If only the adder part counts, recovery finishes only at the end of the fiscal year. If all ΔkW revenue counts, the picture changes completely. Tokyo's year-2 upper limit is ¥30,245,391. If 2 MW wins every slot at September's Tokyo primary offline average of ¥8.58, each slot brings in ¥17,160, and the limit fills in about 1,763 slots — around 37 days. On that reading, you would bid under a ¥0.33 ceiling for most of the year.
7. For owners and buyers
Set from published figures, the adder is in the ¥1 range even in year 1 and below ¥1 from year 2 — an order of magnitude below the ¥10 cap. The figures on this page are a guide to the lower end of the ceiling; if you can identify blank items such as personnel and aggregator costs from breakdowns, it rises by that much. Whether you can identify the items is, directly, your room to price.
When buyers build their models, the safe choice is not to set the ΔkW price at the ¥10 cap but at the lower of the actual price in their area (50-4 Market) and the height the formula in the text can explain. How depreciation is set changes the adder, and the treatment when immediate depreciation is used is unsettled. The incentive is summarised in COLUMN 45.
Every calculation can be reproduced with our public script (scripts/column50/ceiling_calc.py in the scix-web repository; inputs in inputs.json in the same place).
Sources
- METI, “Balancing Market Guideline” (需給調整市場ガイドライン), revised 13 March 2026, pp. 6–7 https://www.egc.meti.go.jp/info/guideline/pdf/20260313001a.pdf
- OCCTO, “Adjustment coefficients for the capacity market main auction for FY2029” (31 July 2025) https://www.occto.or.jp/assets/market-board/market/jitsujukyukanren/files/2029_chouseikeisu.pdf
- OCCTO, Form 2, “List of parameters for calculating expected capacity etc. (delivery year FY2029)”, firm resources (pure pumped storage and batteries) https://www.occto.or.jp/assets/market-board/market/youryou-system/youryousystem_sankatouroku/files/2029_youshiki2_yousui.xlsx; supplementary explanation (July 2025) https://www.occto.or.jp/assets/market-board/market/youryou-system/youryousystem_sankatouroku/files/2029_sanko_youshiki2.pdf
- OCCTO, “Capacity market main auction results (delivery year FY2029)” (20 January 2026, corrected 23 January) https://www.occto.or.jp/assets/various/capacity-market/jitsujukyukanren/2029_jitsujukyu_kanren/260123_mainauction_youryouyakujokekka_kouhyou_jitsujukyu2029.pdf
- OCCTO, briefing material “On the capacity market main auction” (July 2025), p. 22 https://www.occto.or.jp/assets/market-board/market/oshirase/2025/files/20250709_youryou_seidosetsumei.pdf
- METI, “Current status and issues of stationary storage systems” (12 March 2025, Document 6), p. 5 https://www.meti.go.jp/policy/mono_info_service/joho/conference/battery_strategy2/shiryo06.pdf
- Agency for Natural Resources and Energy, “On the Long-term Decarbonization Power Source Auction” (21 June 2023, Document 7) https://www.meti.go.jp/shingikai/enecho/denryoku_gas/denryoku_gas/seido_kento/pdf/081_07_00.pdf
- EGC, “Explanatory material for generators on the generator-side charge (example)” (January 2025, partly revised May 2026) https://www.egc.meti.go.jp/info/public/pdf/20250121002a.pdf; each general transmission and distribution operator's wheeling terms and unit prices (TEPCO Power Grid, “Wheeling Service Terms”, versions effective 1 October 2026 and 1 November 2026 https://www.tepco.co.jp/pg/consignment/notification/index-j.html, among others)
- Local Tax Act, Article 350 (fixed asset tax rate); Ministerial Ordinance on the Useful Lives of Depreciable Assets, Appended Table 2 (e-Gov law search); Fixed Asset Valuation Standards, Appended Table 15 (residual value rates)