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.
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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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.
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Free Solar PV CalculatorsA 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. BSI - PAS 63100:2024 - Protection Against Fire of Battery Energy Storage Systems for use in DwellingsThis Publically Available Specification (PAS) from the British Standards Institution (BSI) was sponsored by The Department for Energy Security and Net Zero. Although not yet a British Standard, this guidance was developed in response to an urgent demand for clarity as to good practice across the industry including product, service and process standards. Flat Roof: Solar PV Array Spacing / Shade CalculatorThe 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. Ground Faults, Isolation (ISO) Faults, RISO Low Faults and Insulation Resistance Faults with Solar PV SystemsAfter a number of years exposed to wind, rain, snow, ice and sometimes animals; solar panel systems can start to develop faults. The most common faults we find related to exposure are ground faults, isolation (ISO) faults, RISO low faults and insulation resistance faults. In this article we take a look at what these faults are, the possible causes and what steps are taken to identify and resolve them. |
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