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Solar Panels - PV System Sizing and Power Yield Calculator

A simple PV array size (metres, sq m, kWp) and power output (kWp, kWhrs) calculator. The given measurements are for unobstructed areas of space to be made available for solar photovoltaic (PV) panels. Solar PV panels are mounted on-roof using aluminium rails, roof hooks and clamps.

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 including mounting equipment and example power output figures (kWhrs) are provided for each system.

Solarworld 235Wp - 250Wp Mono Black Solar Panel

Solar panel details:(based on the 245W, Mono, Black):

  • Length: 1675mm
  • Width: 1001mm
  • Depth 31mm
  • Output: 245Wp
Alpha On-Roof Solar PV Mounting System

Mounting details:

  • Roof mounted (based on theOn-Roof mounting system)
  • Tiled roof with wooden rafters
  • South Facing
  • 30° roof pitch
  • No shading

Energy output estimates are based on general SAP 2009 calculations for a south facing UK tiled roof with a 30° pitch. The SAP 2009 calculation is:

0.8 x kWp x 1073 (S-solar radiation) x 1 (ZPV-overshading factor)

Solar Panels can be mounted in portrait or landscape to 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.

This calculator should only be used for quick reference; please see system design or contact us if you would like more detailed power estimates and roof designs tailored to real roofspaces, factoring in equipment specifications, the arrays location and the roof aspect (E, S, W).

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 0.98kWp 841 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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Glen Freeman

About the author:

Glen Freeman is a solar PV systems designer, experienced installer, qualified electrician and Director of In Balance Energy.

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