Free Solar PV Calculators, Design Tools and Software (2023)

Below is a list of free solar calculators that can be used in the design of solar PV systems. These calculators are free to use or download, all excellent resources for anyone looking to install or understand more about solar PV systems.

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PVGIS Estimation Utility

The PVGIS Estimation Utility is a great way to understand a proposed solar PV system's relationship with the sun based on it's location. If you have an understanding of this relationship as well as the access to the historical solar radiation data for your location that the PVGIS provides, you can prepare power output estimates (kWhrs), optimise system designs and have a very good idea of how a solar PV system will perform at a given location before a solar PV system is commissioned.

Using this utility will give you the basic information needed to work out (1) the optimum pitch of a solar PV array based on it's location and height above sea level, (2) the amount of solar radiation available to a given location and (3) an estimated power output figure for your proposed solar PV system. Understanding the movement of the sun over a solar PV installation site is key to optimising the performance and power generation of a PV system, the PVGIS is a great tool to use for this.


This tool underestimates the efficiency of modern solar panels and overestimates (default settings) the power losses that we would expect from a well designed solar PV array. That said, when used as a tool to really understand what's going on between a solar PV array, it's location and the sun, it's superb.


Free Solar PV Calculators, Design Tools and Software (3)

Free Solar PV Calculators, Design Tools and Software (4)

SMA Sunny Design

SMA is the world's leading manufacturer of solar PV inverters and solar PV monitoring systems. SMA's Sunny Design software is a free to download and an incredibly powerful solar PV calculation tool.

SMA Sunny Design software generates detailed .pdf reports based on simple inputs such as the number and type of panels used in the design, the basic location details, the aspect i.e. (N, S, E, W) and the roof pitch. The software also helps in cable size calculations to minimise power losses.

A nice feature we have found when using this software is the ability to directly compare the performance of different solar panel types, makes and models directly against the details of the solar PV installation site. Most solar PV manufacturers panels and modules are already listed in the SMA Sunny Design database, you also have the option to input your own solar PV module data.


Only applicable to solar PV systems that use SMA inverters. Location details are quite general, the design will be based on the solar radiation data available for the nearest large town to the installation site.


In Balance Energy - Solar PV System Sizing & Yield Calculator

Our very own calculator for working out roof layouts, solar panel numbers and system sizing. Decidedly low tech, but positive feedback from clients who use it has convinced us that it is useful, unique and worthy of being on the list.

This calculator will help you to quickly work out how many large (60 cell) solar panels could fit onto a roofspace if the basic roof measurments (length x width) are known. In addition to module numbers, the range of different layouts that could be used in the system design are illustrated with pictures. Figures are also provided for power outputs (kWhrs) based on SAP 2005 calculations.

A helpful calculator that will provide the base information needed to get the most out of the calculators described above in relation to individual roofspaces.


Will not give 100% accurate measurements for all large solar panels which come in a range of sizes. Unable to design non square PV arrays for example when mounting solar panels on gable ends. SAP calculations underestimate anticipated system outputs especially for systems installed in the south of the UK.


Free Solar PV Design Tools and Software

The design tools and software listed below are free general tools that also lend themselves nicely to be used as solar PV system design tools.

Free Solar PV Calculators, Design Tools and Software (7)

Google Sketchup

Google Sketchup is a fantastic free design and drawing tool that enables the user to create very accurate 3D models and drawings.

The interface is intuitive and the program is very quick and easy to learn, much more akin to drawing on paper than you might find with CAD type programs. We regularly use Sketchup in our PV system designs and when designing custom components.

Using sketchup is a great way to involve clients in the design process and illustrate how solar PV systems will look and integrate into properties before ordering. It also gives the PV system designer the ability to deal with every minor detail of an installation in advance, saving time and potential complications for the installers on-site.


Very few limitations with the free version, the only reason we ever need to use Sketchup Pro (the paid for version, which costs around £350) is for the ability to convert 3D models to 2D for labelling and to accurately print to scale for planning permission documents etc. Nearly all the good stuff comes with the free version.


Free Solar PV Calculators, Design Tools and Software (8)

Google Earth

Google Earth is a firm favorite of ours and a free software program that we couldn't do without. A huge amount of preparation work can be carried out in advance of a solar site survey using the aerial images and location details that are provided by Google Earth.

Google Earth allows you to search for and zoom into a location using a postcode, an address, a town name, grid co-ordinates etc and see a detailed view of what's there from above (a satellite view).

For those involved with solar installations nearly all the information and tools you need to know about a location pre-survey is available via Google Earth at the click of a mouse.


Free Solar PV Calculators, Design Tools and Software (9)

Carbide Depot Trigonometry Calculator

We have been using this simple but effective free web tool for years. Always available with no annoying ads. Perfect for quickly working out roof measurements and roof pitches. Carbide Depot have also built a length, area conversion tool and loads of other calculators and tools to use when working with metal.


Free Solar PV Calculators, Design Tools and Software (10)

MyElectrical Cable Size Calculator

Another free tool we have been using for years, unlike other cable size calculation tools this cable size calculator allows you to work with industrial sized cables and get the complete picture of how a specified cable will perform in terms of voltage drop, within its location and the proximity of other cables all on a single page.

The most thorough cable size calculator we have found. MyElectrical has also built useful tools for conduit sizing and unit conversion.


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The success of any renewable energy project is always in the quality and robustness of the system design, our experienced in-house design team has been designing innovative and ground breaking solar PV and other renewable energy systems since 2007.

We take a collaborative and open approach and often find the very best systems are those where the system owner/developer has taken an active involvement with the design.

We can help prepare cost effective designs, roof layouts and documentation for all types and size of solar PV project; including drawings, bills of materials and detailed custom installation/owners manuals. We work with installers and developers as well as private clients and businesses, so if you need any technical information prepared then contact us, we have specialist knowledge and experience at your disposal, you will find us easy to work with and happy to help.


If we are supplying systems and equipment to Solar PV installers or for DIY solar installations, we are always happy to include system designs, testing and bespoke documentation as part of the package.

This can include:
  • System Performance Statements
  • Line Drawings and Schematics
  • Roof Layouts
  • Grid Connection Documents
  • Solar Panel Testing and Records

Further reading and calculators related to designing, installing, repairing and maintaining solar photovoltaic and electrical systems:

Types of Solar Photovoltaic (PV) System

Introduction to the different types of Photovoltaic (PV) System available including Grid Tied, Off-Grid, Hybrid and Batteryless solar PV systems.

Engineering Recommendation G98

Grid Connections for Micro-Generators including Solar PV Systems and Elecricity Storage Systems in the UK. Under 16Amps Per Phase, grid synchronised.

Solar PV System Components

Overview of the basic components needed to install a complete solar PV system. Introduction to solar PV panels. power inverters, AC & DC isolators and mounting systems.

(Video) Solar Design Software Popular PV Tools for Simulation

Solar PV: Smart Export Guarantee

Interesting times ... The Smart Export Guarantee came into affect in January 2020. The Smart Export Guarantee is an obligation set by the government for licensed electricity suppliers to offer a tariff and to pay small-scale low carbon Generators and Micro-generators for any electricity that they export to the National Grid.

Evaluating Solar PV Panels - Which panels to buy?

What to look for when evaluating and selecting solar PV panels for UK installations. Electrical characteristics of solar PV arrays and the safety factors used for selecting BoS equipment, also mounting options.

Solar Panels - PV Array Calculator

Solar Panels: Solar PV System sizing and power yield calculator. Use to work out roof layouts, PV array sizes, No. of panels and power yields. Based on SAP 2009.

Flat Roof Solar PV Array Spacing / Shade Calculator

The minimum required space between parallel rows to avoid shading is decided by the height of the array immediately in front, the slope of the roof and the lattitude of the installation site. This table illustrates the different row spacings required for optimum positioning in different locations.

Solar Electricity - Frequently Asked Questions (FAQs)

How to size a system?, What is kWp?, What is the difference between a kilowatt (kW) and a kilowatt hour ( kWh)?, How does a solar PV system work? Can I add more solar panels to my system? How do I know if my solar panels are working?

Preparing for a Solar Panel Installation

As with any construction project the success and efficiency of a solar PV panel installation comes down to good planning. Some advice for potential system owners preparing for a new solar panel installation.

Planning Permission for Solar Photovoltaic (PV) Systems

A solar PV installation can be classed as 'permitted development' subject to conditions and when not located within a conservation area, AONB or world heritage site.

Residential PV systems notifiable under Part P. Special consideration needed for Part A. A combination of serious risks for solar PV installers.

(Video) Solar Calc Photovoltaic Calculation software

Safely Retrofitting Solar PV Roof Mounts

The things to consider before installing a retrofited solar PV system on a roof and an introduction to the type of equipment used to secure an on-roof solar PV system.

Smart Switching / Solar PV Power Switching

Available as an addition to existing solar PV systems or installed as a package alongside a new system, Smart switching puts full control of a solar PV system's power output firmly in the hands of the system owner.

An alphabetical list of many of the industry and technical terms you are likely to come across when installing a solar PV system. The glossary also defines terms that are used in roofing and electrical work as well as in solar PV installation and solar manufacturing.

Mains Supply and Earthing Systems: Location & accessability, supply systems, earthing, bonding, labelling, installing RCDs.

A quick overview of some common electrical warning signs and labels that you might find attached to electrical equipment.

ABB / Power One Aurora Inverter Faults and Repairs

Power One, at one point were the second ranked inverter manufacturer in the world and there are many Power One Aurora Inverters installed in the UK. The most popular models being the Uno PVI-3.0-TL-OUTD and the Uno PVI-3.6-TL-OUTD.

Fronius IG / IG Plus Inverter Faults and Repairs

Fronius IG and IG Plus series inverters have LCD displays on the front of the chassis that providing it's working, will highlight any errors with the inverter or the solar PV system that it runs.

Mastervolt Inverter Faults and Repairs

Mastervolt Sunmaster and the smaller Soladin ranges of inverters were widely installed in the UK between 2011 and 2014. Popular Sunmaster models being the Sunmaster XS2000, Sunmaster XS3200 and the Sunmaster XS4300.

(Video) Solarius PV - The Solar PV calculation software - ACCA software

SMA Sunnyboy Inverter Faults and Repairs

SMA Sunnyboy Inverters have been widely installed in the UK, some of the most popular being the SB1200, SB2000 and SB3000. High frequency models include the SB2000HF, SB2500HF, and SB3000HF. Transformerless models include the SB3000TL and the SB3600TL.

SolarEdge Inverter and Optimser Faults and Repairs

The SolarEdge system is unique and in our opinion unrivalled in terms of it's ability to monitor system performance down to panel level. This is achieved through the installation of a small unit called an optimiser.

Sonnen Macht Inverter Faults and Repairs

The problem we often find with these inverters are damaged relays, the tell tale sign of a relay failure is an Error 19: Relay or Error 19: Relay Fault warning displayed on the inverter's display.

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Areas Served:

Swindon: Abingdon, Aldbourne, Andover, Banbury, Basingstoke, Bath, Berkshire, Bicester, Blunsdon, Box, Bracknell, Bradford on Avon, Bristol, Burford, Calne, Camberley, Carterton, Cheltenham, Chippenham, Chipping Norton, Chipping Sodbury, Cirencester, Corsham, Cricklade, Devizes, Didcot, Evesham, Faringdon, Fleet, Gloucester, Gloucestershire, Hampshire, Henley-on-Thames, Highclere, Highworth, Hook, Hungerford, Keynsham, Kingsclere, Lambourn, Lechlade, Lyneham, Maidenhead, Malmesbury, Marlborough, Marshfield, Melksham, Minety, Newbury, Oxford, Oxfordshire, Pewsey, Purton, Ramsbury, Royal Wootton Bassett, Salisbury, Shalbourne, Slough, Stow, Swindon, Tewkesbury, Thatcham, Trowbridge, Wanborough, Wantage, Warminster, Wiltshire, Winchester, Windsor, Witney, Wokingham, Worcester, Wroughton and Yate.


Which software is used for designing a PV system? ›

SolarEdge Designer is a free web-based solar design tool that helps solar professionals like yourself lower PV design costs and generate winning customer proposals.

What is the best solar PV design software? ›

Best PV System Design Software for Your Solar Business
  • Aurora. 7.2 /10.
  • Sighten. 6.8 /10.
  • Open Solar. 8.4 /10.
  • Solar Nexus. 7 /10.
  • PVSol. 9.1 /10.
  • Helioscope. 7.4 /10.
  • PVsyst. 5 /10.
  • Solargraf. 8.6 /10.

Is easy PV free? ›

Registration takes mere seconds, simply sign up for a free account at Easy-PV. Create your first project and have a play!

How can I design my solar system? ›

  1. Determine power consumption demands. The first step in designing a solar PV system is to find out the total power and energy consumption of all loads that need to be supplied by the solar PV system as follows: ...
  2. Size the PV modules. ...
  3. Inverter sizing. ...
  4. Battery sizing. ...
  5. Solar charge controller sizing.

What are the best solar calculator? ›

5 best solar estimators & savings calculators
  • Google Project Sunroof (<1 min to estimate) ...
  • PV Watts (<1 min to estimate) ...
  • EnergySage (<1 min to estimate) ...
  • (3 min to estimate, must sign in with email) ...
  • Sunpower (3 min to estimate, must give personal info)
31 Jan 2021

What is PVsyst software? ›

PVsyst is the most widely used solar simulation software for the energy yield estimation and For optimal design of solar power plants. This software is used by almost all the known solar energy companies.


1. Solar Calc. Photovoltaic Calculation software
(acerielectrical ed)
2. Introducing AcSolarate Lite PV system design excel based tool
(Sun Revolt)
3. Solar PV System Calculations and Design - Practical Way
(Free Online Courses)
4. Understanding of Tilt angle, Azimuth angle and Base slope of a Solar Module in Pvsyst software
5. Solar Design Tool software demo
6. Free Rooftop Solar Plant Calculator | Free TOOL | Investment Return Period | Free Download
(Sustainable Every Day)
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