LIVE SOLAR RESOURCE · PVGIS 5.3 · LOCATION-BASED MODEL
Solar PV Calculator by Location
Choose a country and major city to load live solar-resource data from the European Commission's PVGIS database. The calculator uses the location-specific PV yield to size a system and estimate annual production, first-year savings and simple payback.
1. Choose the solar-resource location
Not in the list? Enter coordinates for your locality. The tool will calculate PVGIS data for the exact coordinates and show the nearest major reference city in our list.
Source: PVGIS 5.3, European Commission Joint Research Centre.
2. Size the PV system and estimate payback
Enter your electricity use and your own local project economics. Use the same currency for installed cost, electricity price, export credit and incentives.
Estimated monthly PV production
Load solar data and calculate a system to see monthly production.
Worked example: turning a PVGIS yield into a system size
The location step and the project-economics step are deliberately separate. PVGIS supplies a specific annual yield for a 1 kWp reference system at the selected coordinates and orientation. WattCostLab then divides your target annual solar energy by that specific yield, rounds the result up to a whole number of panels, and recalculates annual generation from the actual rounded system size.
For an illustrative example, suppose PVGIS returns 1,500 kWh/kWp/year for the chosen coordinates and settings. This is a hypothetical yield used only to demonstrate the calculator; your live PVGIS result can be higher or lower. With 10,000 kWh/year of household use, 100% target coverage and 450 W panels:
- Unrounded requirement: 10,000 ÷ 1,500 = 6.67 kW DC.
- Whole-panel sizing: 6.67 kW requires 15 × 450 W panels, so the installed model size becomes 6.75 kW DC.
- Annual generation after panel rounding: 6.75 × 1,500 = 10,125 kWh/year.
Now assume an installed cost of $3.00/W, no upfront incentive, an electricity price of $0.173/kWh, 70% self-consumption, no export credit, 2% annual electricity-price escalation and 0.5% annual PV degradation. The modeled net project cost is $20,250. First-year self-consumed production is 7,087.5 kWh, worth about $1,226/year at the entered retail rate; generation exported at a zero credit contributes no first-year bill value. The resulting simple payback is about 16.5 years. Under those same escalation and degradation assumptions, the model produces a positive 25-year net benefit of roughly $16,565.
What changes the result most
Self-consumption and export compensation can matter as much as sunshine. If exported electricity is credited below the retail rate, a system that produces more annual kWh is not automatically the system with the shortest payback. Likewise, panel-count rounding can make actual modeled production slightly higher than the target coverage entered above.
The 25-year result is scenario-based, not a forecast. Electricity-price escalation and PV degradation compound over time, so small changes in those assumptions can materially alter long-run value. Simple payback uses first-year bill value only; it does not discount future cash flows or include financing interest.
What the location model does not include automatically
The calculator does not automatically add financing fees, taxes, maintenance, inverter replacement, insurance changes, battery cycling costs or site-specific construction extras. Shading and roof geometry are represented only to the extent captured by the selected PVGIS orientation/horizon settings; a detailed site survey can identify obstructions and electrical constraints that a location model cannot.
Use the result as a benchmark for comparing installer proposals. A quote should state the proposed DC size, panel count, expected annual kWh, orientation assumptions, export/net-metering treatment and complete installed cost so you can compare like with like. The solar-resource data source remains PVGIS, European Commission Joint Research Centre.
If your city is not listed
Use My locality is not listed and enter latitude/longitude, or use the approximate-location option. The calculation is then made for those coordinates rather than for a nearby city. The nearest major reference city is shown only as a geographic reference.
Why this is more accurate than a generic “sun hours” calculator
PVGIS calculates location-specific solar radiation and photovoltaic production using its radiation databases, terrain horizon information and PV-system models. The result returned here is the annual PV yield for a 1 kWp reference system, which WattCostLab scales to the system required by your electricity use.
How payback is estimated
First-year bill value separates PV electricity used directly in the home from exported electricity. Self-consumed energy is valued at the entered retail electricity price; exported energy is valued at the export-credit rate. The 25-year projection applies the entered electricity-price escalation and PV degradation rates. It does not model financing interest, taxes, maintenance, inverter replacement or battery cycling unless those costs are included in your installed project cost.
Primary data source
PVGIS — European Commission Joint Research Centre. PVGIS provides solar radiation and PV performance information for locations around the world, except the poles.
Frequently asked questions
What if my locality does not appear in the city list?
Enter the locality's latitude and longitude or use the approximate-location option. The tool calculates PVGIS data for those coordinates and then displays the nearest city in the reference list.
Does the calculator use average solar radiation or current weather?
It uses the long-term solar-resource and PV-performance data returned by PVGIS for the selected coordinates, not today's weather.
Why does the calculator ask for self-consumption and export credit?
A kilowatt-hour used directly in the home can have a different financial value from a kilowatt-hour exported to the grid. Separating them makes the payback estimate more transparent.
Can I use a roof direction instead of the optimal PVGIS angle?
Yes. Select the custom-roof option and enter roof tilt and compass direction. PVGIS then calculates the yield for that plane.
Ready to compare solar quotes?
Use the location-based result as a benchmark, then compare installer system size, annual kWh estimate, electrical scope and project cost.
WATTCOSTLAB / EXTERNAL EXPLAINER
Watch: How solar panels work
Solar panels convert sunlight into electricity through photovoltaic cells. This short explainer provides physical context for the solar-resource and production assumptions used by the location-based payback calculator above.
External educational video by TED-Ed. The video explains the concept; use the WattCostLab tools and inputs on this page for your own rates, location and assumptions. Watch on YouTube.
Solar payback: separate resource quality from project economics
Reviewed September 14, 2026. The solar-resource layer uses PVGIS irradiation, while installed cost, retail electricity price, export credit, incentive and self-consumption remain editable economic assumptions. Keeping those layers separate makes the result auditable and prevents a location dataset from being mistaken for a contractor quote.
European Commission JRC PVGIS → · Test tilt and orientation →