From rain to sunshine: How much power does a 5 kW solar produce?

5 kW solar panels

How much power does 5 kW solar panel produce everyday?

You may have thought about buying a solar power system, may be a 5 kW, or smaller. That’s because solar panels save money on your power bill by reducing your import. And, they also produce clean electricity. 

If you did some research, you’ll quickly find out that there are different kinds of solar panels; different sizes, different brands, different technology, and for different applications.

Today I will talk about traditional solar panels designed for residential homes. Also, I will tell you how much energy to expect from a 5 kW system.

If you are like most Aussies, you consume about 18 kWh of energy per day. And, with solar you’ll be able to replace some or most of that energy, thus saving money on the bill. 

You would know that you need ‘X’ number of panels if you knew how much one panel produced. 

Let’s start from the basic….

How are solar panels rated for power?

Solar panels get labeled for maximum output they can produce under ‘perfect’ conditions. Furthermore, the maximum output, also known as power rating (or wattage), is found under technical specs of the product or as a key feature..

power-rating-250watts-panel

solar-panels-size

The most commonly available solar panels in the market are between 250 to 300 wattage.

Perfect condition

Here are four conditions that ‘perfectly’ enable solar panel to produce at its full potential.

  1. North facing
  2. Inclined at the same angle as latitude.
  3. Sun is at the strongest, technically it’s called Peak solar radiation (1kW/m2); 
  4. Panel Surface temperature at 25 degree celsius.

 solar-panel-rating-solar-insolation

 

A solar panel rated 275 watts will produce 275 watts-hour in an hour, under these ideal conditions. Likewise, 1 kilowatt solar panels will produce one kilowatt-hour in an hour. 5 kW will produce 5 kWh in an hour.

If you are not so sure about kilowatts vs. kilowatts-hour, please read this: Do you get confused by kW and kWh all the time?

How many solar panels is 5 kW?

5 kilowatt is five thousand watts. For simplicity, let’s look at one kilowatt….

Here are different ways to get 1000 watts solar panels…

100 watts X 10 panels
200 watts X 5 panels
250 watts X 4 panels
300 watts X 3.33 panels

You’ll have three to four solar panels on your residential rooftop system for each kilowatt you purchase. That means you’ll end up with 15-20 panels for a 5 kW system.

To add up the watts from all solar panels, they are connected in series (also known as string) during installation.

one-kilowatt-solar-panels-connection

Daily production from 5 kW solar panels

Before we jump into how much 5 kW will produce, there is something you should know: Daily Solar insolation, which is the amount of sunlight hitting a surface on a daily basis.

In the diagram below, the shaded area under the curve is the total solar insolation for a day. You can see peak solar radiation occurring around midday. And most of day, solar radiation is below the peak.

solar-peak-radiation-and-solar-insolation

Let’s say that we measured solar insolation of 4200 watt-hour in a day, on a surface area of one square meter. That’s same as saying 4.2 kWh/m2.

Now, this is a bit tricky…. If peak solar radiation is 1 kW/m2, we can re-write 4.2 kWh/m2 to 4.2h X 1kW/m2 and say that there were 4.2 hours of peak solar radiation. Does it make sense?

Numerically, the amount of sunlight scattered across many hours of the day is same as what it would be in 4.2 hours if the sun is at its strongest.

For all calculation purposes, scientists and experts convert total daily insolation into the number of hours with peak solar radiation.

Peak Sun Hours (a.k.a. PSH)

Peak solar radiation hours is known as Peak Sun Hours or PSH. In the example above, 4.2 is the number of Peak Sun Hours.

See below… if we re-draw the diagram above to show in PSH, it would look something like below.

how-to-calculate-peak-sun-hoursPeak Sun hour (PSH) is a standard universal metric that is used to calculate solar output. For example, we are told by meteorologist/related authorities that Melbourne has daily PSH of 3.6 hours.

Output calculation

To determine how much a 5 kW system would produce in a day, we simply multiply 5 kW by PSH; in case of power generation in Melbourne that would be 5 kW X 3.6 hours = 18 kWh. 

Places like Brisbane and Perth produce more solar electricity per kW than Melbourne. That’s because solar insolation is more in those location; more sunshine. 

Solar output published by Clean Energy Council 

Clean Energy Council (CEC), the peak body for renewable energy in Australia, has made everyone’s life easier by publishing how much energy one should expect from systems of different sizes.

For example, it says a 5 kW system in Brisbane will produce 21 kWh on average everyday of the year. These numbers are average for the year – so summer months will produce more and  winter months will produce less.

The table below is the data published as guidelines by CEC for different sizes of solar system.

Note: CEC mentions that output is achieved in perfect lab conditions. That means, if you recall, these are outputs from solar panels that face north, inclined at latitude angle, and temperature measuring 25 degree on panel’s surface. In reality, you can expect the actual output to be slightly different from these numbers.

  

City1 kW system1.5 kW system2.0 kW system3.0 kW system4.0 kW system5.0 kW system
Adelaide4.2 kWh6.3 kWh8.4 kWh12.6 kWh16.8 kWh21.0 kWh
Alice Springs5.0 kWh7.5 kWh10.0 kWh15.0 kWh20.0 kWh25.0 kWh
Brisbane4.2 kWh6.3 kWh8.4 kWh12.6 kWh16.8 kWh21.0 kWh
Cairns4.2 kWh6.3 kWh8.4 kWh12.6 kWh16.8 kWh21.0 kWh
Canberra4.3 kWh6.45 kWh8.6 kWh12.9 kWh17.2 kWh21.5 kWh
Darwin4.4 kWh6.6 kWh8.8 kWh13.2 kWh17.6 kWh22.0 kWh
Hobart3.5 kWh5.25 kWh7.0 kWh10.5 kWh14.0 kWh17.5 kWh
Melbourne3.6 kWh5.4 kWh7.2 kWh10.8 kWh14.4 kWh18.0 kWh
Perth4.4 kWh6.6 kWh8.8 kWh13.2 kWh17.6 kWh22.0 kWh
Sydney3.9 kWh5.85 kWh7.8 kWh11.7 kWh15.6 kWh19.5 kWh

For example, based on the data in the table, a 5 kW solar system in Melbourne can power a Sharp microwave (800 watts) for 22.5 hours. Likewise, A 3 kW system would power the same microwave for 13.5 hours (10800 watt-hour/800 watts).

5 kW-solar-production

 

What happens in cloudy and rainy days?

Automatically, there is very little sunshine. However, there is still some light energy hitting the solar panels.

Unlike what most people think, solar panels can still produce between 10-20% of the maximum energy output during bad weather days. However, it is a very small amount.

Solar production also varies each month of the year. Just to give you an idea, I have included a  chart below. It shows daily output from a 5 kW system in Melbourne for each month of the year.

Note: The data source, PVwatts, mentions that the output on a monthly data can vary by +/- 30% real world. This is to be used only as a guide.

 

5-kw-solar-output

Melbourne has harsh winter weather. While the days are shorter, there is plenty of cloud coverings as well. You can expect May, June, and July months to produce 40-50% of the level in January.

Summing up..

You should understand that the actual useable output from a 5 kW system can vary from above figures depending on the quality of panels, and their ability to handle various system inefficiencies. Furthermore, some of the power is wasted in the form of heat, especially in the summer. That is why CEC and PVwatts production values are close estimates and should be used only as guidelines.

There you have it…write me if you have any questions.

Share this page

Leave a Reply

Your email address will not be published. Required fields are marked *