Methodology — v0.1

How we measure a megawatt.

Every figure Joule publishes comes from public market data and a reproducible model. This page is the complete method — so your team can check our numbers before you ever talk to us.

Data window: Jun 2025 – Oct 2026 · Sources: EPEX / SEMOpx / regelleistung.net / SEM Committee · Status: living document

M—01Reference site

All figures refer to a standardized 10 MW AI datacenter (IT capacity, meter side scaled by PUE 1.25):

Load class	IT capacity	Utilization	Flexibility
Inference — tier 1 (real-time)	4.75 MW	diurnal profile	none
Inference — tier 2 (async / batch)	0.25 MW	diurnal	minutes-scale
Training	4.0 MW	75% target	hours-to-days deferrable
Base (cooling, network, storage)	1.0 MW	constant	none

Training energy is conserved: 72 MWh per day must be delivered within each 24-hour window — flexibility means when, never whether.

M—02Data sources

Day-ahead spot prices — EPEX (DE-LU, FR) via the public energy-charts.info API; SEMOpx for the Irish SEM. Uniform hourly resolution throughout.
Ancillary capacity prices — regelleistung.net (German TSO joint platform), twelve months of weekly tenders, FCR and aFRR.
Capacity market parameters — SEM Committee auction information packs and decision papers (CRM T-4 2028/29, 2029/30).

M—03Dispatch model

Two scheduling strategies compete on identical data:

oracle: fill each day's 72 MWh of training into that day's cheapest hours (water-filling) — the theoretical upper bound
naive: fill the fixed night window 22:00–06:00 first — the heuristic operators actually use

Capture rate = realized savings ÷ oracle savings, against a flat-schedule baseline. All accounting is energy-conserving at uniform hourly resolution.

M—04Results

Market	Oracle savings / yr	Share of power bill	Naive capture
Ireland (SEM)	€815k	9.6%	~33%¹
Germany (DE-LU)	€938k – €1.12M	12–14%	~51%
France (FR)	€740k – €0.99M	15–17%	~46%

The naive baseline's annual figure conceals a structural split: it captures 85–97% in winter (wind makes nights cheap) but only 20–35% in summer (solar makes midday cheap). The optimizer's edge concentrates exactly where value is most volatile.

Ancillary and capacity layers — FCR at a measured €141.9k/MW/yr, aFRR at €50.7k/MW/yr, Irish CRM clearing at €135.5k/MW/yr — are inaccessible to any fixed-schedule strategy. Naive capture there is not 50%. It is zero.

Stacking the dispatchable share of these layers on top of arbitrage brings the total annual value pool for the reference site to ≈ €1.0–1.4M, depending on market and registered flexible capacity (3.6 MW of 10 MW in this configuration). Site-specific figures are computed, not extrapolated, in every audit.

M—05Limitations

Oracle is an upper bound; production systems are gated at ≥60% capture.
Hourly resolution understates intraday optionality; telemetry-grade modeling ships with audits.
Irish spot series ends May 2026 pending ENTSO-E access; figures marked ¹ reflect that window.
No storage assumed. Storage-backed configurations unlock FCR symmetry and are assessed per site.

Questions, replication attempts, disputes: hello@joule-os.com. We answer all three.