Free Solar PV
Yield Simulator
& Calculator
Rensys is a free solar PV simulator and calculator. Pick a location, set your system size, tilt, and orientation, and get annual yield, specific production, and a monthly profile in seconds. Built on real irradiance data and engineer-checked formulas. For a side-by-side look at the options, read Rensys vs other PV simulation tools. Free to use, and if you need a full design, leave it to us.
Rensys v1.1
Free solar PV calculator and photovoltaic system simulation by Renwaves
Rensys is a free, browser-based PV simulator for estimating solar energy production and system performance.
Location
No location selected. Using default irradiance.
System Parameters
Monthly Energy Production Profile
Ready for user input.
Features of the free Rensys solar PV calculator
Explore the key factors behind a solar installation and turn location and system assumptions into a clear first estimate of energy production.
Location-Based Solar Data
Search for a city or address to estimate solar potential using location-specific irradiance data.
Flexible System Parameters
Adjust system capacity, module technology, panel tilt, azimuth, inverter efficiency, and irradiance assumptions.
Fast Yield Calculations
Estimate annual and average daily energy yield with a performance ratio based on the selected inputs.
Monthly Production Profile
Review an at-a-glance monthly energy profile to understand how production may vary through the year.
Instant Browser Workflow
Run a simulation directly in your browser without installing desktop software or setting up a project.
Clear, Practical Results
Use the outputs for an initial feasibility check, then move to a detailed engineering design when needed.
Built in the Open
Rensys is a free, open-source PV simulation project. Explore the repository, review the current implementation, and follow development or report issues on GitHub.
Rensys vs PVsyst: a free alternative for quick estimates
Rensys is built for the first step: a fast, free yield estimate. Full simulation software is for the final design. Start here, then go deeper when the numbers justify it.
| Rensys | PVsyst | |
|---|---|---|
| Cost | Free | Paid license |
| Setup | None | Desktop install |
| Time | Seconds | Hours |
| Best for | Early estimate | Detailed design |
PVsyst is a trademark of PVsyst SA. Comparison is for general guidance only.
A free solar PV calculator for quick yield estimates
Rensys is a free solar PV simulator that runs in your browser. Choose a location, enter your system size, tilt and azimuth, and estimate annual energy production in kWh alongside a monthly production profile. No installation or account is required.
Use local solar-resource data to get an initial picture of your site’s production potential.
Explore how capacity, panel orientation and other assumptions affect your estimated yield.
Use the estimate for an early feasibility check before moving to a detailed PV design.
Rensys, answered
Quick answers about how the simulator works and what it can and cannot do.
01How accurate is the Rensys solar PV calculator?
Rensys is a screening tool, so expect roughly ±15 to 20%. It uses long-term average irradiance and a simplified loss model. A full design replaces those assumptions with your real site data and reaches ±6% model accuracy.
02Where does the solar data come from?
When you search a location, Rensys pulls long-term average irradiance for that point from NASA POWER. The monthly profile in the chart follows the same data. You can also type your own irradiance value if you have a more local source.
03What do tilt and azimuth change?
They set how much sunlight your panels catch. Rensys picks a tilt close to the yearly optimum for your latitude. An azimuth of 0° means the array faces the equator, which is south in the northern hemisphere and north in the southern.
04What does Rensys leave out?
It does not model shading, soiling, hourly weather, or panel degradation separately. Temperature effects are covered by the module technology factor and a fixed performance ratio. For shaded or complex roofs, a full design is the safer route.
05Is the Rensys PV simulator free, and is my data saved?
It is free to use. The calculator runs in your browser and does not save your inputs. Location searches are sent to third-party services (Open-Meteo and NASA POWER) to return coordinates and solar data.
06Can I use the results for permits or financing?
No. Rensys is meant for early estimates only. Permits, bank loans, and installer quotes need a full design with a shading model, stringing, and a single-line diagram. You can request a full PV system design from our engineers.