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Solar Panels - PV System Sizing and Power Yield Calculator

Updated: December 2019, inc updated solar panel outputs and irradiance datasets

How many solar panels are needed to power a house? How much space is needed to put solar panels on a roof? Home much power will a new solar PV system produce?

The simple PV array size calculator below roughly estimates the amount of space a solar power system will take up on a roof and the amount of power the system might generate.

The given measurements are for unobstructed and unshaded areas of south facing roofspace i.e. ideal roofspace for installing solar panels. Any deviation from due south will see a reduction in power. Lower pitched roofs and roofs pitched at 45 degrees or greater than the 30 degrees used in the illustration, will also see a reduction in overall power generation.

The more directly a solar panel faces the sun, the more light the panel will receive, the more power it will produce. It can achieve this best and will generate the most power throughout the course of the day by facing South. This being said East/West combinations can also be sensible design choices when based on a well matched time of day power usage requirement.

This calculator will definitely not be accurate for any real world system and should only be used to get a very quick idea of how much space a solar panel system might take up on a roof and how much power different combinations of solar panels will produce over a year.

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Use this calculator to quickly estimate how many large solar panels you could fit onto a roof and roughly calculate how much power they could generate (kWhrs). The number of panels, the roof layout, the overall system size allowing space for roof mounting equipment and example power output figures (kWhrs) are provided for each system.

Solar panels: Length: 1675mm, Width: 1001mm, Output: 320 Watts (per panel)
Mounting: Roof mounted, South Facing, 30° roof pitch, No shading or obstructions.

MCS Irradiance Dataset: Zone 5E - Bristol and surrounding areas.

Source: MCS Irradiance Datasets

Energy output estimates are based on the following calculation:

kWhrs (kilowatt hours generated over a year) = kWp (max system size in kilowatts) x kk (Annual Solar Radiation (source: MCS Irradiance datasets) x SF (Shading Factor)

Solar Panels can be mounted in portrait or landscape to best fit the available space. The quickest way to use the calculator is to start from the width, then the height of the available mounting area and match the system size from there. Remember, where possible it is better to allow for space between the panels and the eaves, ridge and sides, mainly so wind can't get behind them and put pressure on their mountings.

This calculator should only be used for quick reference; let us know if you would like us to prepare something more accurate.

Links to other useful free tools can be found here: Free Solar PV Calculators

Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 4 4 4.06m 1.68m 6.82m sq 1.280kWp 1233.92 kWhrs
Portrait 2 4 8 4.06m 3.37m 13.68m sq 1.96kWp 1682 kWhrs
Portrait 3 4 12 4.06m 5.06m 20.54m sq 2.94kWp 2524 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Landscape 1 3 3 5.06m 1m 5.06m sq 0.735kWp 631 kWhrs
Landscape 2 3 6 5.06m 2.02m 10.22m sq 1.47kWp 1262 kWhrs
Landscape 3 3 9 5.06m 3.04m 15.38m sq 2.2kWp 1888 kWhrs
Landscape 4 3 12 5.06m 4.06m 20.54m sq 2.94kWp 2524 kWhrs
Landscape 5 3 15 5.06m 5.08m 25.7m sq 3.67kWp 3150 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 5 5 5.08m 1.68m 8.53m sq 1.22kWp 1047 kWhrs
Portrait 2 5 10 5.08m 3.37m 19.55m sq 2.45kWp 2103 kWhrs
Portrait 3 5 15 5.08m 5.06m 25.7m sq 3.67kWp 3150 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 6 6 6.1m 1.68m 10.25m sq 1.47Wp 1262 kWhrs
Portrait 2 6 12 6.1m 3.37m 20.56m sq 2.94kWp 2524 kWhrs
Portrait 3 6 18 6.1m 5.06m 30.87m sq 4.41kWp 3786 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Landscape 1 4 4 6.76m 1m 7.92m sq 0.98kWp 841 kWhrs
Landscape 2 4 8 6.76m 2.02m 13.66m sq 1.96kWp 1682 kWhrs
Landscape 3 4 12 6.76m 3.04m 23.76m sq 2.94kWp 2524 kWhrs
Landscape 4 4 16 6.76m 4.06m 27.45m sq 3.92kWp 3365 kWhrs
Landscape 5 4 20 6.76m 5.08m 34.34m sq 4.9kWp 4206 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 7 7 7.12m 1.68m 11.96m sq 1.71kWp 1468 kWhrs
Portrait 2 7 14 7.12m 3.37m 23.99m sq 3.43kWp 2944 kWhrs
Portrait 3 7 21 7.12m 5.06m 36.03m sq 5.14Wp 4412 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 8 8 8.14m 1.68m 13.68m sq 1.96kWp 1682 kWhrs
Portrait 2 8 16 8.14m 3.37m 27.43m sq 3.92kWp 3365 kWhrs
Portrait 3 8 24 8.14m 5.06m 41.19m sq 5.88kWp 5047 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Landscape 1 5 5 8.45m 1m 9.9m sq 1.22kWp 1047 kWhrs
Landscape 2 5 10 8.45m 2.02m 19.8m sq 2.45kWp 2103 kWhrs
Landscape 3 5 15 8.45m 3.04m 29.7m sq 3.67kWp 3150 kWhrs
Landscape 4 5 20 8.45m 4.06m 34.31m sq 4.9kWp 4206 kWhrs
Landscape 5 5 25 8.45m 5.08m 42.93m sq 6.1kWp 5236 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 9 9 9.16m 1.68m 17.82m sq 2.2kWp 1888 kWhrs
Portrait 2 9 18 9.16m 3.37m 35.64m sq 4.41kWp 3786 kWhrs
Portrait 3 9 27 9.16m 5.06m 53.64m sq 6.61kWp 5674 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Landscape 1 6 6 10.14m 1m 10.14m sq 1.47kWp 1262 kWhrs
Landscape 2 6 12 10.14m 2.02m 20.48m sq 2.94kWp 2524 kWhrs
Landscape 3 6 18 10.14m 3.04m 30.83m sq 4.41kWp 3786 kWhrs
Landscape 4 6 24 10.14m 4.06m 41.17m sq 5.88kWp 5047 kWhrs
Landscape 5 6 30 10.14m 5.08m 51.51m sq 7.35kWp 6309 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 10 10 10.18m 1.68m 17.10m sq 2.45kWp 2103 kWhrs
Portrait 2 10 20 10.18m 3.37m 34.31m sq 4.9kWp 4206 kWhrs
Portrait 3 10 30 10.18m 5.06m 51.51m sq 7.35kWp 6309 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 11 11 11m 1.68m 19.8m sq 2.69kWp 2541 kWhrs
Portrait 2 11 22 11m 3.37m 39.6m sq 5.39Wp 4627 kWhrs
Portrait 3 11 33 11m 5.06m 59.4m sq 8.08kWp 6936 kWhrs
Panel Orientation No. Panel Rows No. Panel Columns Total No. Panels PV Array Width PV Array Height Mounting Area (m2) Max Power (Wp/kWp) Output (kWhrs, Year)
Portrait 1 12 12 12.22m 1.68m 20.53m sq 2.94kWp 2524 kWhrs
Portrait 2 12 24 12.22m 3.37m 41.18m sq 5.88kWp 5047 kWhrs
Portrait 3 12 36 12.22m 5.06m 61.83m sq 8.82kWp 7571 kWhrs

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Mains/Grid Isolation and Surge Protection

Mains/AC Surge Protection Solar PV Systems

A whole house surge protector is installed to provide protection from transient overvoltages originating from the mains/grid. A whole house surge protector is installed directly inline and as close as possible to the incoming mains/grid supply meter, this allows for surge protection for all circuits and equipment including solar inverters, routers, stereos and other sensitive electrical equipment within the network. The addition of a 100Amp lockable isolator also allows for safe and convenient isolation of all electrical equipment within the network including consumer units, solar inverters, battery storage units and EV chargers from the mains/grid in one place.

Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671.

Mains/Grid Isolation and Surge Protection

 

Solar PV Surge Protection (DC Surge Protection)

DC Surge Protection Solar PV Systems

DC surge protection devices (SPDs) are installed between the solar panels and the solar inverter to protect both the inverter and the downstream electrical equipment from transient overvoltages of an atmospheric origin impacting the electrical system via the DC side of the system / the solar panels.

DC Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671.

Solar PV Surge Protection (DC Surge Protection)

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Articles: Further Information, Calculators & Inverter Fault Codes

Lots of articles, calculators and technical information including links for further reading. Covering a range of topics related to the installation and maintenance of solar photovoltaic and electrical systems in the UK.

/Solar PV Information Articles

Free Solar PV Calculators

A list of free solar PV calculators, solar design tools and software, Use to calculate solar yields and the Return on Investment (ROI) for solar PV systems.

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.

Mains Power Supplies & Earthing Systems

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

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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, Reading, Royal Wootton Bassett, Salisbury, Shalbourne, Slough, Stow, Swindon, Tewkesbury, Thatcham, Trowbridge, Wanborough, Wantage, Warminster, Wiltshire, Winchester, Windsor, Witney, Wokingham, Worcester, Wroughton and Yate.

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