Should You Over-Size Your PV Array?


Before tackling the question whether or not you should Over-Size your PV Array, lets first explain what it means to have an Over-sized PV Array.

Over-sizing your PV array is when the total capacity of your PV array (solar panels) exceeds the size of your inverter. The way to check your PV array size is by multiplying the capacity (wattage) of a solar panel by the number of panels you have or plan to install. You can then compare this to the size of the inverter to distinguish whether you have over-sized your PV array (most inverters will have their size labelled on the component itself if you don’t already know).

So, if you have 20 x 250w panels, your full panel capacity would be 5kW. In many cases this is when households would typically opt for a 5kW inverter, so not to overload the inverter or waste energy.

However, what most people don’t know is by exceeding your inverters size with a few additional panels you can increase your inverters efficiency, increase your potential savings and reduce your bills further without breaking the rules on grid connection restrictions or damaging the inverter.

In fact, a 5kW inverter could take an additional 4 panels (totalling 24) equalling the panel’s capacity of 6kW.

Increase Inverters Efficiency

It’s rare that solar panels will generate energy at their maximum capacity due to so many external factors that can cause a drop. These factors can include weather, temperature, dust, shade etc. When power going to the inverter is under 30% of its capacity the efficiency* of the inverter drops. By having extra panels your system will generate more energy meaning the inverter will be converting energy at a higher percent with less chance of an interrupted drop.

*The efficiency of an inverter indicates how much DC power is converted to AC power.

In the case that your panels exceed the capacity of your inverter, any good quality inverter should be able to handle the excess (although it will essentially be wasted energy).


Increase Your Potential Savings & Reduce Bills Further

More panels equals more energy generated and more generated energy means less reliance on the grid, which in turn will reduce your power bills, giving you more savings. Annually you’d expect a 5kW inverter with a 6kW PV array to generate approximately the same amount of electricity that a 6kW inverter with a 6kW PV array would. This comes in handy when the grid you are connected to has restriction on what size you are allowed for your property.

Over-sizing Without Breaking Grid Connection Restrictions

In Australia there are restrictions on what size solar system you can have if you are grid connected. This is a restriction that energy retailers and the Clean Energy Council have put in place to avoid any disruption to the grid. Depending on which grid you are connected to the size restriction may vary, however for a single-phase home the maximum size is typically a 5kW inverter per property. If these restrictions are breached you are unable to claim any of the Solar Government incentives that are available in Australia. However a loophole around this restriction, which is stated in the Clean Energy Solar PV Design Guidelines is you can over-size your inverter by 33% meaning you can have a 5kW inverter with a PV array of 6.6kW. This will give you the benefits of a 6.6kW system without breaching any grid restrictions. 

What Are The Disadvantages to Over-sizing?

Wasted Energy (clipped)

Whilst over-sizing your system by 33% won’t harm a quality inverter that is installed properly, there is potential for excess energy to be wasted. In perfect weather conditions (clear sky, 25-degree day) if your panels are generating energy in excess to the capacity of your inverter this excess power will be lost. When energy is lost from an over-sized PV array is is known as “clipped off” in the industry. While this is not ideal the occurrence of perfect conditions with no external factors hindering your PV array energy output is rare.

Lifespan of Inverter

By sticking within the regulations of over-sizing no more than 33% of your inverters capacity you will prevent any significant change to the inverter’s lifespan.

Benefits Outweigh the Disadvantages

Overall over-sizing your solar system can be hugely beneficial when staying within the Clean Energy Council guidelines. Not only is it a way to combat the grid restriction of a 5kW system, but it will maximise your inverters efficiency and generate more energy for your household with no to minimal risk.


Start Speaking To Installers About Your System Size Options!

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Understanding Batteries

Off-Grid Systems

For some households a battery system can be of great benefit and minimise a home’s reliance on the grid. However, it’s important to understand for a battery to be useful your solar system needs to be generating excess energy for the battery to store, which you can then use at night or when the sun is not out.

When selecting a battery, you’ll want to invest in a system that is most suited to your home and can drive the best return on investment (ROI). Despite a larger upfront cost, a higher quality battery may significantly increase your ROI.

    Battery systems start from $6,000 and costs can vary greatly based on the following factors:

  1. Cycle Life-Time

    The number of times a battery can fully charge and discharge.

  2. Battery Power (kW)

    How fast it can be charged or discharged.

  3. Storage Capacity (kWh)

    The maximum amount of energy a battery system can store.

  4. Battery Management System (BMS)

    An electronic ‘smart’ system that gathers data and manages the battery ensuring it does not overload or operate outside of its safe functioning zone..

  5. Inverter

    Battery systems require their own inverter if your solar system does not have a hybrid inverter.

  6. 'All-In-One Unit’

    A system which includes the battery, BMS and an inverter all in one unit.

  7. Warranty

    Length of time or cycles the battery system is under guarantee.

  8. Blackout Protection/Backup

    It’s important to note this is not a common feature of a battery system and could cost thousands of dollars to include. Blackout protection not only requires additional components but also a specialised installation and rewiring. For grid-connected homes, the cost for blackout protection can outweigh the benefit.

Additionally, if your purpose for adding battery is to go Off-Grid and become completely independent from the grid you will need to ensure your solar system can generate enough energy to power your home and your battery system is large enough to store this energy. For homes in metro areas going Off-grid is not cost effective and is only recommended for those in remote areas with limited access to the grid. Off-grid solar systems with battery start at approximately $30,000.

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