Root-mean-square error (RMSE) against Transelectrica's own published day-ahead forecast, same delivery slots, same information cutoff. Public data. Leak-safe, vintage-controlled — the weather each forecast used was frozen to what was knowable at gate time, never the realized weather. Out-of-sample test window, 2026. Losses shown, not hidden.
Positive = we beat Transelectrica's own published forecast for the same delivery slots, at the same information cutoff. Lead is how far ahead the forecast is issued.
| target | 1h | 2h | 3h | 4h | 8h | 16h | 24h (day-ahead) |
|---|---|---|---|---|---|---|---|
| solar | +70% | +66% | +65% | +64% | +64% | +64% | +65% |
| wind onshore | +30% | +19% | +12% | +9% | +5% | +2% | -1% |
Source manifest: experiments/x02/asof_engines_ro.json (LightGBM residual,
ENTSO-E actuals, ICON-EU + ECMWF-IFS + GFS vintage weather, n ≈ 15,500 test points/cell).
Solar skill is flat across every horizon — ~+70% at 1 hour, still ~+64% at 24 hours. That flatness is the proof it is bias-correction, not weather leakage. Leaked future weather would inflate the long horizons and then collapse under a leak-safe rebuild — which is exactly what happened to the German and Belgian solar numbers when we ran the same audit on them. Romania's solar survived it intact, because the edge never came from weather at all; it came from correcting a broken incumbent forecast.
We checked the obvious artifact too: solar is zero at night, which is trivially easy to predict. Restricting the score to daylight-only slots gives the same +64% — the skill is real daytime accuracy, not a night-zeros illusion.
Wind day-ahead is honest parity. Romanian onshore wind shows a real short-horizon nowcasting edge (~+31% one hour ahead) that decays to roughly zero by the day-ahead horizon — Transelectrica's wind forecast is decent, so there is no standing bias to exploit. We report it at parity and do not claim a day-ahead wind win. (This is the mirror image of Belgium, where wind survived the audit and solar did not.)
Not yet live on a Romanian market. This is a backtest on public data — rigorous, reproducible, leak-safe, but a backtest. Our live track record is on Belgian solar, where we submit hourly probabilistic forecasts to Elia's Predico platform and have ranked as high as 4th of 30 forecasters. A live Romanian feed is the natural next step.