Compute capture price, capture rate (a.k.a. value factor / quality factor / Marktwertfaktor), TBx battery-arbitrage spreads, and other generation-weighted market metrics server-side from landed Parquet. Use this instead of fetching hourly prices + hourly generation yourself and weighting them client-side — server-side aggregation has no row cap and no pagination.

slug: a key from list_derivations() — today: "capture_price", "negative_price_hours", "residual_load", "res_share", "emissions", "tb_spread".

tb_spread returns monthly (default) or annual (aggregation='annual') Top-Bottom spreads TB1/TB2/TB4/TB6 in /MW per period — the sum of daily (top-x minus bottom-x hourly prices) over SDAC market days. The only slug accepting aggregation, and the only one accepting multi-zone zone ('all', a list, or CSV). Example — annual TB2 across every European market in ONE call: get_derivation("tb_spread", "2025-01-01", "2026-01-01", zone="all", aggregation="annual") For a single day's top/bottom hour TIMESTAMPS use get_tb_spread.

capture_price returns monthly rows per (zone, psr_type, currency) with columns: currency, capture_price_eur_per_mwh, baseload_price_eur_per_mwh, quality_factor (the capture rate = capture/baseload), total_gen_mwh, n_hours. Months are bucketed by local time using the zone's IANA timezone.

ENDED INPUTS: when an input series stopped upstream before the window's end, the answer carries series_ended (per zone for a multi-zone tb_spread): which inputs, why, what carries each on, and any metric that carries this one on. GB: ENTSO-E's day-ahead price ended 2020-12-31, so GB capture_price, negative_price_hours and tb_spread stop there; capture_price_mid covers GB 2016-09 → now against the Market Index Price (a traded index, not the auction — read its note).

CURRENCY (capture_price and tb_spread alike): the *_eur_per_mwh / tb*_eur_per_mw key names are FIXED for API stability and do NOT track the actual unit — read the row's currency column, which is authoritative (EUR for euro zones, GBP for GB, PLN/RON/BGN for the PL/RO/BG local-currency eras). The response echoes it top-level as currency; a window spanning two currencies instead sets unit to null with mixed_currency: true and a currencies list. A month (or period) spanning a redenomination splits into one row PER CURRENCY, each computed only from that currency's hours — so never average or sum a price column across rows with different currency values. Summing total_gen_mwh across them IS correct: the split rows partition the month's hours rather than duplicating them. quality_factor is a ratio and stays comparable across currencies.

emissions returns monthly rows per (zone, psr_type) with columns: generation_mwh, n_hours, emission_factor_kg_per_mwh, emissions_t_co2. Production-based; IPCC AR5 lifecycle factors. Zero-emission rows (nuclear, wind, solar, hydro, geothermal, marine) appear with emissions_t_co2 = 0 — useful for stacked charts.

Filter via psr_types=["solar","wind_onshore","wind_offshore"] (or raw B-codes like "B16") to get only the technologies you care about. Defaults to all psr_types that have generation data.

Example — Spain solar capture price, last 12 months: get_derivation("capture_price", "2025-05-01", "2026-05-01", zone="ES", psr_types=["B16"], tz="Europe/Madrid") Example — Germany 2024 emissions by fuel: get_derivation("emissions", "2024-01-01", "2025-01-01", zone="DE_LU", tz="Europe/Berlin") Returns 12 monthly rows in one call; no pagination.