PVGIS Tutorial: Calculate Your Solar Yield in 5 Minutes

PVGIS is the most important free tool for estimating the yield of a planned photovoltaic system – developed by the European Commission’s Joint Research Centre, scientifically sound, and usable without registration. Yet many users struggle with its dry interface or fall into the azimuth trap. This tutorial walks you step by step through a correct yield calculation and shows you how to interpret the results properly.

Step 1: Open PVGIS and Set Your Location

Open the tool at re.jrc.ec.europa.eu/pvg_tools/en/. The interface is available in several languages (selector in the top right).

You can set your location in three ways:

1. Address search: enter street and town in the search box and click “Go!”
2. Map click: click directly on your roof in the map
3. Coordinates: enter latitude and longitude manually

The selected point determines which irradiance data PVGIS uses. House-number precision is unnecessary – the satellite data has a resolution of several kilometers anyway.

Step 2: Choose the Right Tool

PVGIS bundles several calculators into tabs. For a classic rooftop system you only need the first one:

Tab	Purpose
Grid connected	Standard rooftop system with grid feed-in – the normal case
Tracking PV	Systems with sun-tracking modules (ground-mounted)
Off-grid	Standalone systems with battery (garden shed, camper van)
Monthly/Daily data	Raw irradiance and temperature data
Hourly data	Hourly values as CSV – basis for your own simulations
TMY	”Typical Meteorological Year” for download

Select “Grid connected” for the following calculation.

Step 3: Enter Your System Data

Now come the five decisive inputs:

Solar radiation database

Keep the default (for Europe: PVGIS-SARAH3). It is based on satellite measurements and is the most accurate option for Central Europe.

PV technology

“Crystalline silicon” is correct for over 95% of all modern modules – both monocrystalline and polycrystalline.

Installed peak power (kWp)

Enter the planned system size in kWp, e.g. 10 for a 10 kWp system. Note: this is the module peak power (kWp), not the inverter rating.

System losses

The default of 14% covers cable, inverter, and soiling losses and is slightly conservative. For new systems with high-quality components, 10–12% is reasonable. Important: temperature and low-irradiance losses are calculated by PVGIS additionally and automatically – don’t count them twice!

Slope and azimuth

• Slope: roof pitch in degrees (typical pitched roof: 30–45°, flat roof with mounting frames: 10–15°)
• Azimuth: here lurks the most common mistake. PVGIS uses 0° = south, -90° = east, +90° = west – not the compass rose!

Then click “Visualize results”.

Step 4: Interpret the Results Correctly

PVGIS returns a compact results box and several charts. The key figures:

Yearly PV energy production

The central value: the expected annual yield in kWh. For a 10 kWp system in Germany it ranges between 8,500 and 11,000 kWh depending on location and orientation – the regional differences are explained in our article on solar irradiance in Germany.

Divide this value by the system size to get the specific yield in kWh/kWp – the most important metric for comparing locations and quotes (Germany: 900–1,100 kWh/kWp).

Year-to-year variability

The standard deviation between individual years – typically ±400–600 kWh for 10 kWp. It shows that even at the same location, yield fluctuates by about ±5–10% from year to year. A single weak year is therefore no cause for alarm.

Monthly chart

The bar chart shows the typical seasonal distribution: May through August deliver more than half the annual yield, while December and January together contribute only 4–6%. A detailed overview with reference values is available in Monthly Solar Yield.

Loss breakdown

Below the chart, PVGIS lists the calculated losses: angle of incidence (AOI), spectral effects, temperature and low irradiance, plus your specified system losses. This transparently shows how global irradiance turns into final yield.

Avoid These Common Mistakes

1. Misreading the azimuth – the classic (see above)
2. Ignoring shading: PVGIS only knows horizon shading from terrain, not your neighbor’s tree or a dormer. With relevant near shading, increase the loss factor or have a professional run the numbers.
3. Confusing kWp with kW: enter the module peak power, not the inverter rating.
4. Counting losses twice: temperature losses are included automatically – don’t add them to the 14% system losses.
5. Treating the average as a guarantee: PVGIS delivers long-term expected values, not a guarantee for any specific year.

Limits of PVGIS – and What the Alternatives Do Better

PVGIS is excellent for initial planning, but has inherent limits:

Requirement	PVGIS	Better alternative
Yield estimate for a new system	✅ ideal	–
Near shading (trees, buildings)	❌	professional planning, 3D tools
Day-by-day production forecast	❌	Solar Forecast based on weather models
Economics (self-consumption, storage, costs)	❌	Solar Calculator
Hourly profiles for your own simulations	✅ (CSV export)	–

Conclusion

PVGIS delivers a scientifically sound yield estimate for any location in five minutes – free and vendor-neutral. The keys to correct results: respect the PVGIS azimuth convention (0° = south), use realistic system losses, and account for near shading separately. For economic analysis and day-by-day forecasts, combine PVGIS with specialized tools.

Key takeaways:

• PVGIS calculates annual and monthly yield from long-term satellite data (±5% accuracy)
• Azimuth convention: 0° = south, -90° = east, +90° = west
• The default 14% system losses fit most systems; temperature is handled automatically
• PVGIS can’t do near shading or economics – that’s what the Solar Calculator and Solar Forecast are for