Solar noon is the moment each day when the sun is at its highest point in the sky for your location, due south in the UK. It is when a fixed, south-facing panel produces the most, and it rarely lands exactly at 12:00 on the clock because of your longitude, the equation of time, and British Summer Time.

Why is solar noon not at 12:00?

Two reasons. Your longitude shifts it: places west of the Greenwich meridian, like Cardiff or Plymouth, reach solar noon a little later than London. And the equation of time, caused by the Earth's tilt and elliptical orbit, moves it by up to about 16 minutes across the year. British Summer Time then adds an hour to the clock reading from late March to late October.

How does solar noon help size plug-in solar?

Solar noon and day length tell you when and for how long a fixed panel sees the strongest sun. A south-facing balcony or wall produces a peak around solar noon, so matching your daytime usage to that window raises self-consumption, which is what makes plug-in solar pay. For a location-specific yield and savings figure, use the postcode calculator.

What are peak sun hours?

Peak sun hours are the equivalent number of hours per day at full 1,000 W per square metre that would give the same total energy as the real day. It is a modelled figure from satellite irradiance, not a clock time, and it varies by location and season. The postcode calculator uses PVGIS satellite data to estimate yield from peak sun hours for your address.

Solar Noon Calculator UK: Sunrise, Sunset and Solar Noon by City

How to read this. Solar noon is when the sun is due south and highest, the daily peak for a fixed south-facing panel. Sunrise and sunset bracket the generating window. Day length and the noon elevation tell you how strong and how long that window is, which is why both swing so much between a Plymouth June and an Aberdeen December.

What solar noon is, in plain terms

Solar noon is the instant the sun reaches its highest point in your sky each day. In the UK that is when it sits due south. It is the moment a fixed, south-facing balcony or wall panel hits its daily peak, because the panel is pointed closest to the sun. It is not usually 12:00 on your clock, and the gap is predictable, not random.

Why it is rarely exactly 12:00

Three things move it. Your longitude shifts solar noon by four minutes per degree, so a western city like Cardiff or Plymouth reaches it later than London. The equation of time, a wobble caused by the Earth's tilt and its elliptical orbit, moves it by up to about 16 minutes either way across the year. And from late March to late October, British Summer Time adds an hour to the clock, so solar noon reads closer to 13:00 than 12:00 in summer.

Why this matters for plug-in solar

A plug-in or balcony kit only pays when you use the power as it is generated, because most early UK kits do not pay for export. Generation peaks around solar noon and tapers towards sunrise and sunset, so the more of your daytime usage, the fridge, the washing, the work-from-home load, you can line up with the hours either side of solar noon, the higher your self-consumption and the better the maths. Day length sets the outer limits: a long June day gives a wide window, a short December day a narrow one.

Want the savings number, not just the times? This page gives you the sun's timing. For a location-specific yield and payback estimate, the postcode calculator pulls PVGIS satellite irradiance for your coordinates and models self-consumption, battery storage and smart tariffs. For the method behind both tools, see how we track the sun.

Common questions

Solar noon is the moment each day when the sun is at its highest point in the sky for your location, due south in the UK. It is when a fixed, south-facing panel produces the most, and it rarely lands exactly at 12:00 because of your longitude, the equation of time, and British Summer Time.
Your longitude shifts it: places west of the Greenwich meridian, like Cardiff or Plymouth, reach solar noon a little later than London. The equation of time moves it by up to about 16 minutes across the year. British Summer Time then adds an hour to the clock reading from late March to late October.
Solar noon and day length tell you when and for how long a fixed panel sees the strongest sun. A south-facing balcony or wall peaks around solar noon, so matching your daytime usage to that window raises self-consumption, which is what makes plug-in solar pay. For a location-specific yield, use the postcode calculator.
Peak sun hours are the equivalent number of hours per day at full 1,000 W per square metre that would give the same total energy as the real day. It is a modelled figure from satellite irradiance, not a clock time, and it varies by location and season. The postcode calculator uses PVGIS data to estimate yield from peak sun hours for your address.

How this is calculated

Solar noon, sunrise and sunset use the standard NOAA solar position equations: the equation of time and the sun's declination for the chosen date, combined with your city's latitude and longitude. British Summer Time is applied automatically for dates between the last Sunday of March and the last Sunday of October. Sunrise and sunset use the conventional 90.833 degree zenith, which includes atmospheric refraction and the sun's radius. Figures are to the nearest minute and are a model, so they can differ from an almanac by a minute or so.

Sources

NOAA Global Monitoring Laboratory solar calculations, the equations used here.
European Commission PVGIS, the satellite irradiance behind the yield figures on the postcode calculator.
Plug Solar Hub: how we track the sun.

What solar noon is, in plain terms

Why it is rarely exactly 12:00

Why this matters for plug-in solar

Common questions

How this is calculated

Sources

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