What is a peak sun hour?

Published: 23 November 2021

A peak sun hour is any hour of the day when the sunlight’s intensity is an average of 1000 watts of energy per square meter.

Peak sun hours usually start from noon and last till early afternoon. The peak sunlight hours at your location determine if it’s worth buying a solar system or not.

If you’re considering getting a solar system, you’re on your way to making the right decision. 

However, before you opt for solar, it’s important to consider if your home gets enough sunlight, that is, the peak sunlight hours.

Luckily, Australia is no short of peak sun hours, and therefore, it is an ideal location for placing solar panels and generating power from them. 

However, it’s still important to consider your location, weather conditions, and climatic seasons to see if your house gets enough peak sun hours to generate efficient solar energy.

So, how exactly can you calculate peak sun hour? And is your location ideal for solar? 

We’ll answer all your questions in the following guide. 

What is a peak sun hour in solar?

A peak sun hour is described as the hour of the day in which the sunlight’s intensity is near an average of 1000 watts of energy per square meter. This amount of sunlight is also the amount that is required to test and rate solar panels.

To put in simple words:

One peak sun hour is equal to 1000 W/m2 of sunlight per hour.

In this way, the term peak sun hours describes the solar insolation that a particular area will attain if the sun shines at its maximum value for a particular number of hours. 

The peak solar radiation is calculated to be 1 KW/m2. So, you’ll notice that the average daily solar insolation and peak sun hours are numerically identical.

For instance, you can describe a location getting 8 KWh/m2 per day as receiving 8 hours of sunlight every day at 1 KW/m2.

How peak sun hours are calculated for a location

During the late afternoon, sunlight is usually less than 500 W/m2. But during clear, sunny midday, you might receive more than 1000 W/m2. These numbers can be expressed in peak sun hours.

For instance, receiving 500 W/m2 in the morning for an hour is equal to 0.5 peak sun hours.

Similarly, if a location gets a total of 5,900 W/m2 of solar radiation for an hour over the course of the day, then it will get 5.9 peak sun hours.

It’s a fact that the sun does not shine at its maximum intensity all day long. 

Instead, the amount of sunlight arriving on the ground continues to fluctuate depending on conditions like time and weather.

What time of day is peak sun?

Peak sun hours usually occur starting from noon till early afternoon when the sun is at its intense and highest position in the sky. 

At sunrise and sunset, the sun is at a low angle, which means that the atmosphere filters most of the sunlight, and a minimal amount of energy reaches the earth.

How many peak sun hours do solar panels need?

Any location getting 4 peak sun hours or more in Australia is considered ideal for producing solar energy. And luckily, there is no scarcity of peak sun hours in Australia.

Let’s explore the peak sun hours for different locations in Australia.

Australia’s average peak sun hours by state

The following table shows the average peak sun hours for different cities and states in Australia. You’ll get a good idea of what might be the peak sun hour in your location.

City, StateAverage Daily Peak Sun Hours (kWh/m2)
Alice Springs, Northern Territory6.5
Darwin, Northern Territory6.2
Cairns, Queensland5.8
Perth, Western Australia5.5
Townsville, Queensland5.4
Brisbane, Queensland5.1
Adelaide, South Australia4.8
Gold Coast, Queensland4.8
Sydney, New South Wales4.5
Melbourne, Victoria4.1
Hobart, Tasmania3.8

(Source: Hot Spot Energy)

Australia enjoys tons of high sunshine hours, although there is a difference in its distribution across different cities. 

Perth is usually the sunniest, receiving 3,200 sun peak hours every year. On the other hand, Melbourne only gets 2,200 hours annually. On average, Australia gets 6 peak sun hours in many of its cities.

Here are the average daily sunshine hours received by various Australian cities across the year:

MonthBrisbaneSydneyCanberraMelbourneAdelaidePerth
January88981011
February7788910
March778689
April777767
May766456
June765345
July775445
August886455
September888567
October888678
November8897810
December8897911

What affects peak sun hours?

The time of day, cloudiness, climatic seasons, geographic location, and solar panel position affect peak sun hours. 

1. Time of day

Solar panels are likely to produce the highest amount of solar energy when the sun is highest in the sky. This time is usually called the solar noon, and it varies from location to location. It is considered ideal for both peak sun hours and solar radiation.  

Here is a table showing the average solar noon time in various locations across Australia from January – December.

MonthAdelaideSydneyCanberraMelbourneHobartBrisbanePerth
January1:19 pm12:58 pm1:06 pm1:23 pm1:14 pm11:51 am12:20 pm
February1:19  pm1:08 pm1:17 pm1:33 pm1:24 pm12:01 pm12:30 pm
March1:27 pm1:05 pm1:15 pm1:32 pm1:23 pm12:00 pm12:28 pm
April1:25 pm11:58 am12:05 pm1:24 pm1:14 pm11:51 am12:20 pm
May12:12 pm11:52 am12:00 pm12:17 pm12:07 pm11:45 am12:13 pm
June12:15 pm11:54 am12:02 pm12:17 pm12:08 pm11:45 am12:14 pm
July12:14 pm12:00 pm12:08 pm12:23 pm12:14 pm11:52 am12:20 pm
August12:21 pm12:00 pm12:09 pm12:26 pm12:17 pm11:54 am12:22 pm
September12:21 pm11:54 am12:00 pm12:20 pm12:10 pm11:47 am12:16 pm
October1:04 pm11:55 am12:04 pm12:09 pm12:00 pm11:35 am12:05 pm
November1:02 pm12:38 am12:47 pm1:03 pm12:54 pm11:31 am12:00 pm
December1:02 pm12:38 am12:52 pm1:09 pm1:00 pm11:36 am12:05 pm

(Source: Geo Time Date)

On the other hand, the sun is at a low angle at sunrise and sunset, so more sunlight is filtered, and less energy reaches the solar panels.

2. Cloudiness

The presence of clouds in the environment also affects solar radiation by diffusing it. In this way, the peak sun hours are reduced. The cloudiness at a particular location is a daily factor. Cloudy and rainy days have fewer peak sun hours. On the other hand, clear days have more peak sun hours.

3. Climatic seasons

In particular seasons, peak sun hours are reduced because of the sun’s position. For example, the sun is at a higher location during the summer seasons, and therefore, you will experience more peak sun hours than in winter.

4. Geographic location

The location has a significant impact on the peak sun hours. Areas closer to the equator get more solar energy because of their proximity to the sun. In this way, regions farther south get more peak sun hours than the areas farther north.

5. Position of your solar panel

Peak sun hours also depend upon where your solar panels are placed. The direction of your solar panels influences the total amount of sunlight it receives, as well as the intensity of the sunlight.

On the other hand, shading also affects the amount of sunlight absorbed by solar panels. For instance, if a tree or other obstruction serves as a shade over the solar panel, it will receive less sunlight.

How to calculate the peak sun hours for your roof?

If you want to calculate your roof’s peak sun hours by yourself, you can use the PVWatts calculator. You can do the calculation by inputting roof measurements with tilt and azimuth, which will give you an estimated value for the average solar radiation by month.

But if you just want to know the solar panel size you should get for your roof, you can simply take advice from Instyle Solar. We’ll help you choose a suitable model and tell you how much power it will generate every month.

Conclusion

Before you get a solar panel, it’s important to ask if your location is ideal for solar energy production and how big your solar panel should be. You will answer these questions when you know the peak sun hours at your location.

A peak sun hour is any hour of the day when the intensity of the sunlight is near an average of 1000 watts of energy per square meter. So, for example, you can describe a location getting 6 KWh/m2 per day as receiving 6 hours of sunlight every day at 1 KW/m2.

Usually, the peak sun hours start from noon and last till early afternoon. This is because the sun is at its highest position during this hour, and the maximum sunlight reaches the earth’s surface. Therefore, you can expect the solar panel to receive the maximum amount of energy during this time.

Australia enjoys a fair amount of peak sun hours all across the year. Although the number of solar hours varies from one location to another, Australia is a good location for solar energy production. Locations near the equator receive more sunlight because they are closer to the sun.

Are you interested in more info about solar energy?

You can learn more about how solar works on this page.

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