[frahlg]

A Swedish household gets back the energy tax on grid electricity that a battery stored and later sent back to the grid (11 kap. 13 § LSE). Core works out the figure for one calendar year in srcfl/ftw#1950, with an account per battery from srcfl/ftw#1953. The two ship in the same Core beta. Fredrik asked on 2 Nov 2026 to carry it into the iOS app.

What changes

• History gets one row under the day: Energy tax refund / Energiskatt tillbaka. It shows only for a home whose price area is SE1 to SE4 and that has a battery. The row asks the box nothing; the screen behind it asks.
• The screen shows one calendar year, last year first:
  • the figure in whole kWh, rounded down, as the box's own page writes it;
  • complete hours of all hours, and "The year is still running" for this year;
  • the battery's size and the least round-trip efficiency the box counted with; with several batteries, a line for each with what came from it, its size and its efficiency, as the box's own History card writes it;
  • each month with its figure and complete hours;
  • the hourly basis as ftw-battery-return-<year>.csv, shared through the system share sheet;
  • that FTW counts low where readings are unclear, that the figure assumes FTW reads every inverter, battery and charger, that an owner can apply for three years after the year ends and the box keeps the hourly readings that long (feat(state): the energy ledger keeps hourly totals for four years ftw#1951), and a link to Skatteverket's rules.
• A year menu offers this year and the three before it.
• When the box sets problem, the screen shows its reason and no figure, and no months: battery_size names the batteries without a size, battery_unread names the drivers in unread, and any reason a later box adds gets a plain sentence.

How it reads the box

Core needs no change. Both routes are Read in api.routes on srcfl/ftw#1950 and #1953, and the passthrough carries text/csv (carriedMedia takes text/*). So the app calls GET /api/energy/battery-return?year= and .csv?year= through api.req. No registry name changes. A box without #1950 answers E_UNKNOWN_OP, and the screen says the box may run older software.

• BatteryReturn (FTWKit/Format) decodes Core's JSON (the batteries list and unread of #1953) and holds the rules: Swedish price area, Swedish calendar years, whole kWh.
• BatteryReturnGlance builds what the screen says, once per answer, year or minute.
• BatteryReturnModel asks through LiveAsk, named by year and hour: once while the screen is open, again for another year or a new hour, never on a timer. It keeps each year's last answer in the sealed home file, so the screen opens on it, dated (SAVED ON THIS PHONE · AS OF …). The file is at version 2, so an answer kept in #1950's first shape is dropped.
• The CSV is read from the box when the share sheet asks for the file, not when the screen opens. SiteModel.readBox returns the raw body.
• Words in English and Swedish in BatteryReturnWords; a test fails on any sentence without Swedish.
• The demo box answers both routes in #1953's shape, with the CSV one row per battery and hour. Two years back it read two batteries; its oldest year has a size for a battery it read nothing from, so the demo shows a reason too.
• -FTWTab refund opens the screen in debug builds, and -FTWRefundYear 2024 picks the year; scripts/demo-screenshots.sh shoots both cases.

Files that open PRs touch: only HistoryTab.swift overlaps (#107). This PR adds three lines to the tab's body and a new view at the end of the file.

Evidence (this Mac)

• swift test in appleApp/FTWKit: 659 Swift Testing tests and 348 XCTest tests green, 16 of them new (BatteryReturnTests, BatteryReturnModelTests).
• xcodebuild for the iOS Simulator: builds with no warnings in the new code.
• Driven in the simulator (iPhone 17 Pro, iOS 26.5, demo): the row opens the screen, the year menu switches years, and Save to Files from the share sheet wrote ftw-battery-return-2025.csv with a header and 8,760 hours. After #1953: 2024 shows two batteries and 2023 the battery_unread reason, in English and Swedish and at the largest text size. A test reads the 2024 CSV: 2 × 8,784 rows, one per battery and hour.
• Launch is untouched, so no LaunchClock numbers.

History, dark	2025, dark	2025, light

Months and notes	Year menu	Share sheet

2026 so far	Swedish, dark	Swedish, light	Swedish, notes

One account per battery (srcfl/ftw#1953):

2024: two batteries	2023: a battery not read	Swedish, two	Swedish, not read	Largest text

Largest text size:

Top, dark	Top, light	Months, dark	History row, light

For review

• The battery check is mine, beyond the brief: a Swedish home with no battery has nothing to claim, so it sees no row.
• The Swedish title is Energiskatt tillbaka; the longer Återbetalning av energiskatt did not fit the bar.
• Real boxes need feat(history): the figure for Skatteverket's energy tax refund after battery storage ftw#1950 and #1953 merged and released first. A box with #1950 alone would show no battery line, since its top-level efficiency and capacity_wh are no longer read; no released box answers that way. The note that the box keeps the hourly readings for the three years an owner can apply is true once feat(state): the energy ledger keeps hourly totals for four years ftw#1951 is in too; it matches the box's own History note there.
• #1950's later fix (b0770337, a device whose identity changed counts as one meter) keeps the JSON shape, so the app needs nothing for it.
• The test of a second launch waits for the home file to land: the file is sealed off the main actor, and under load the second launch could read before it. SavingsModelTests.itOpensOnTheLastAnswer has the same gap.
• Do not merge before Fredrik says so.

🤖 Generated with Claude Code

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Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-02T09:51:57.663084Z	8e20428	PR opened

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