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Long Term Power Forecasts Methodology

Weather-year-based probabilistic forecasts for load, wind, solar, and day-ahead prices, driven by historical weather data and machine learning models.

Written by Raphael Khan

Weather Inputs

Our long-term forecasts extend well beyond the short-term horizon (up to 46 days), covering months and years ahead. We use historical weather years as the basis for every forecast, drawing on historical EC OP forecasts to build our historical weather view.

Data availability varies by model: weather history goes back to 1999 for solar and load, 2006 for hydro run of river, and 2011 for wind - and, as a consequence, price.

Long-term scenarios run on weather years from 2011 to 2025, the period for which wind data is available, generating a rich distribution of plausible futures that reflects the natural variability of weather and is fully accessible to you for scenario analysis.

Forecast Methodology

As with our short-term approach, our long term forecasting combines machine learning and time series analysis, with a strong foundation in fundamental market drivers such as production, consumption, and fuel prices. To ensure transparency and avoid the "black box effect," our models operate in two sequential steps:

Step 1 - Fundamental Forecasts (Load, Wind, Solar)

We begin by generating fundamental forecasts - load, wind generation, and solar generation.

For long-term forecasts, weather inputs come from historical reanalysis data rather than live weather model runs. Each weather year from 2011 to 2025 is treated as an independent scenario and converted into forecasts of demand, wind, and solar production for the next five years. For each year, we apply:

  • Raw hourly weather data from the corresponding historical year (temperature, wind speed, solar irradiance, etc.)

  • Machine learning models trained on recent actuals, ensuring the model reflects the current state of the power system

  • Capacity projections for wind and solar installed capacity, applied forward to reflect the expected fleet size over the forecast horizon

This produces a distinct hourly fundamental forecast for every weather year - 15 scenarios in total - each carrying its own unique intra-day and seasonal shape.

Notes : Forecast quality depends critically on the data used to train the underlying models, so we continuously refine our historical actuals: training relies on recent actuals with an expanding historical window, prioritizing official grid operator data over aggregated sources where available - for example, Ned-NL over ENTSO-E for Dutch wind and solar generation.

Step 2 - Price Forecasts

The fundamental outputs (in MW) are then passed into our machine learning-based price model, following the same two-step architecture as the short-term system. In addition to renewable generation and load, the price model incorporates:

  • Kpler fossil and nuclear plant availabilities

  • Gas forward curve, and coal & carbon fuel prices

Because each weather year produces a distinct set of fundamental inputs, the price model generates a correspondingly distinct price trajectory for each year - capturing realistic intra-day price dynamics (spikes, negative prices, etc.) that a smoothed average profile would mask.

Long-term price forecasts are generated at hourly granularity, and the model is retrained weekly.

Once all 15 weather-year forecasts are generated, we derive a full statistical distribution across them (mean, median, Q25, Q75, min, max), giving you a realistic sense of the range of outcomes that actual weather conditions could produce - anchored in 15 years of observed meteorological data rather than theoretical assumptions.

Note: Long-term hydro run of river and poundage forecasts are not yet fed into the LT price models - only load, solar, and wind currently are.

Scenarization

The real power of the long-term framework lies in scenarization. Because every weather year is forecasted independently, you are not limited to the statistical summaries: you can interrogate any individual year directly, or apply custom scenarios on top of it.

Via the Kpler terminal or API, you can:

  • Compare distributions to assess how sensitive a market is to weather variability: a wide spread between Q25 and Q75 signals high weather sensitivity, while a narrow spread indicates a more weather-resilient market

  • Select any individual weather year (e.g. 2012, the cold winter year) and see what load, generation, and prices would look like if that weather pattern recurred with today's power mix

  • Apply custom scenarios - for example, +10% load growth, modified renewable capacity, or altered fuel prices - across any or all weather years simultaneously

This makes the long-term forecasts a versatile tool not just for "what is the expected outcome" but for answering "what is the range, and what drives it".

Coverage

Zone

Live since

Load

Wind

Solar

Hydro Run of River

Price DA

Albania (AL)

Austria (AT)

2025-08-19

Bosnia and Herzegovina (BA)

Belgium (BE)

2025-07-15

Bulgaria (BG)

2025-08-19

Switzerland (CH)

2025-08-19

Czech Republic (CZ)

2025-08-19

Germany (DE)

2025-07-15

Denmark (DK)

2025-10-31

DK1

2025-10-31

DK2

2025-10-31

Estonia (EE)

2025-08-19

Spain (ES)

2025-07-15

Finland (FI)

2025-08-19

France (FR)

2025-07-15

Georgia (GE)

Greece (GR)

2025-08-19

Croatia (HR)

2025-08-19

Hungary (HU)

2025-08-19

Ireland (IE)

2025-08-19

Italy (IT)

2025-07-15

IT-Calabria

2025-07-15

IT-Centre-North

2025-07-15

IT-Centre-South

2025-07-15

IT-North

2025-07-15

IT-Sardinia

2025-07-15

IT-Sicily

2025-07-15

IT-South

2025-07-15

Lithuania (LT)

2025-08-19

Latvia (LV)

2025-08-19

Moldova (MD)

Montenegro (ME)

North Macedonia (MK)

Netherlands (NL)

2025-07-15

Norway (NO)

2025-10-31

NO1

2025-10-31

NO2

2025-10-31

NO3

2025-10-31

NO4

2025-10-31

NO5

2025-10-31

Poland (PL)

2025-08-19

Portugal (PT)

2025-08-19

Romania (RO)

2025-08-19

Serbia (RS)

2025-08-19

Sweden (SE)

2025-10-31

SE1

2025-10-31

SE2

2025-10-31

SE3

2025-10-31

SE4

2025-10-31

Slovenia (SI)

2025-08-19

Slovakia (SK)

2025-08-19

United Kingdom (UK)

2025-07-15

Kosovo (XK)

Accessing Long-Term Forecasts

Terminal

Long-term forecasts are available directly in the Kpler terminal. You can use the Scenario Builder to create your custom scenarios : choose between individual weather years or statistical views, and apply custom scenarios to model specific assumptions about load growth, capacity, or fuel prices.

API

Long-term forecasts (load, generation, day ahead prices) are queryable across all combinations of:

  • Forecast type: load, wind, solar, price

  • Weather year: individual years (2011–2025) or statistical aggregates (mean, median, q25, q75, min, max)

  • Scenario: custom assumptions (e.g. +10% load) applicable across any weather year

Note : Fundamentals are run once per month, typically on the 1st. The run_date parameter defaults to the closest available run on or before the requested date. Note that ad hoc reruns can occasionally occur - for example, if an issue is identified after a run, we may rerun and produce a run_date that does not fall on the 1st of the month.

For detailed endpoint documentation, refer to the our developer portal

FTP

Long-term forecasts are also available on FTP under :

  • /2_Price/Forecast/Long_Term/COR_E

  • /3_Demand/Forecast/Longterm_Load/COR_E

  • /4_Supply/Forecast/Longterm_Generation/COR_E

File naming conventions:

  • Generation (wind, solar, hydro run of river): CORE_SUPPLY_FORECAST_LongtermGeneration_CORE_{Country}_{Wind|Solar|HydroRunofriverandpoundage}_Hourly_{MEAN|MEDIAN|MIN|MAX|Q25|Q75|REF2XXX}_yyyymmdd.csv

  • Demand: CORE_DEMAND_FORECAST_LongtermLoad_CORE_{Country}_Hourly_{MEAN|MEDIAN|MIN|MAX|Q25|Q75|REF2XXX}_yyyymmdd.csv

  • Price: CORE_PRICE_FORECAST_LongTerm_CORE_{Country}_Hourly_{MEAN|MEDIAN|MIN|MAX|Q25|Q75|REF2XXX}_yyyymmdd.csv

Note : Files are published per run date under each zone/year/month folder (e.g. .../AT/2026/06) and cover the full forecast horizon in a single file. Ignore any legacy files found at the year-level root (e.g. .../AT/2026, dated until 2030) - these predate our 2025-08-18 methodology change, when forecasts were split per horizon instead of by run date.

For questions or feedback, please reach out to your Kpler account manager or contact our support team.

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