What does oversizing a solar power system mean?
When talking to your solar power retailer, they might mention the option of “oversizing” your solar power system. In this article we look at what that means and and if oversizing is right for you.
What is “oversizing” exactly?
At the core of a solar power system, you have panels that generate electricity and an inverter that converts that generated electricity into electricity that you can use to charge your phone and other devices.
Solar panels commonly have a capacity of 300 watt. That means that at peak performance, the panel will produce up to 300 watt. of power. Every panel you add, adds another 300 watt. So, 2 panels produce up to 600 watt, 3 produce up to 900 watt and 22 panels produce up to 6,600 watt.
Inverters also have a capacity threshold, meaning they can only convert a specific amount of electricity coming from the panels. Commonly, the capacity for an inverter is 5,000 watt.
Solar panels however, often don’t perform at their peak output as there’s a variety of influences: time of day, weather patterns – just to name a few. Read our article on output optimisers here.
That means that despite your solar panel array being able to generate up to 5,000 watt, it often isn’t able to generate that exactly. The average amount of electricity generated throughout the day could be much closer to 4,000 watt for example. Nearly 1/5th less than what your inverter is able to handle.
That’s where oversizing comes in. Oversizing a solar power system means you add more panels to a solar power system so that their combined peak output is higher than what the inverter is actually rated for. By doing so, you increase the average efficiency of your inverter.
(RELATED: Is your retailer talking about single phase and three phase? Find out what that means and what you have in this article)
Are you overloading your inverter by “oversizing”?
Any inverter sold in Australia should be able to handle oversizing by up to one-third it’s own capacity without any issues. Assuming your solar power system is designed properly, there aren’t any safety concerns. It is important; however, to make sure the system does not exceed that one-third overload.
Example: A 5 kW inverter should be able to handle up to 6.6 kW, but you shouldn’t go over that.
6.6 kW is an important measurement. It’s the same number as mentioned before, when talking about how much twenty-two 300 watt panels combined generate in electricity. That’s not a coincidence. 5 kW is one of the most popular inverter sizes sold in Australia and many choose to oversize their system to maximise their return.
(RELATED: 3 kW, 5 kW, 6.6 kW or even larger? What size solar power system do you need and what does it cost? You can find all of that out in this article)
What happens with the excess energy generated?
Just because a 5 kW inverter can safely receive up to 6.6 kW from your solar panels, doesn’t mean that it’s able to use all that energy. A 5 kW inverter will still only be able to convert up to 5 kW of electricity coming from your solar panels. If an inverter receives more energy than what it’s rated for, the excess energy will be dumped.
So, using the 6.6 kW system as an example: If you have a 5 kW inverter and you have twenty-two 300 watt panels performing at peak performance, your inverter will convert 5 kW and dump the remaining 1.6 kW.
Why would you choose to oversize your system if excess energy is dumped?
If your solar power system was always performing at peak performance, there wouldn’t be a benefit to oversizing as all of the excess energy produced would be dumped. But between the sunrise, clouds and sundown, there are a lot of moments where some energy will be generated, but not enough to max your inverter.
Your panels won’t generate the same amount of energy throughout the day
Oversizing your solar power system allows you to get more value from those times where your system isn’t performing at peak, and increase the average efficiency of your inverter.
What kind of benefits can you expect from oversizing your system?
Despite electricity being dumped when your panels are performing at peak performance, research has shown that oversizing your solar power system can increase the output of your system by as much as 30%. With 5 kW inverter, that translates to more than $300 per year in extra savings for your average household. More if you consume most of the electricity you generate yourself.
Oversizing is especially interesting when you live in an area that has restrictions on system size. The size of the system is determined by the size of your inverter. In many rural areas for example, 5 kW is the maximum size inverter that you can get installed without requiring additional (expensive) specialised equipment. In these areas, getting 30% more efficiency out of your inverter, makes a big difference.
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