Surely to oversize solar inverters beyond their generation capacity is not necessarily a good idea? Get ready to discover that it’s potentially the best thing you could do, when within specification, and the inverter manufacturers themselves recommend it. Mind blown! Get ready to oversize and thrive.


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Many leading solar inverter manufacturers such as SMA and Fronius suggest that if remaining within the rated voltage and current input ratings of the inverter, oversizing solar inverters by up to 50% is the best way to maximise your solar energy production.

How does oversizing maximise production?

Solar inverters are more efficient when they operate at peak. That’s the consensus. However, the modern-day maximising of production is often based around particular grid or feed-in tariff limitations.

Western Power often will not allow any single-phase solar inverter capacity higher than 5kW output. Three-phase solar inverter capacities are limited depending on localised transformer limitations in which an installation is connected to on the grid.

In an alternative sense, solar inverter capacities which exceed 5kW output capacity are excluded from Synergy‘s feed-in tariff of 7c per unit (kWh) exported to the grid. 

Fronius Solar Inverters Perth WA by Perth Solar Warehouse

How much can one oversize solar inverters?

In theory, as much as possible. Ensuring only the input voltage and current ratings of the solar inverter are not exceeded. Beyond such, alternative external limitations set by national and local regulatory authorities are in place to also limit one’s ability to oversize solar inverters in general.

The simple calculation which can apply to all criteria though is as follows: Solar inverter output capacity multiplied by 1.33 or 33%.

Why is 1.33 a magic number?

1.33 or 33% of a solar inverters rated output capacity has been determined by the powers that be in Australia, as an acceptable oversizing increment without being detrimental to a solar energy systems ability to offset carbon emissions.

Remember, your ability to claim a subsidy on the upfront purchase price of a solar power system is based on its ability to offset carbon emissions now and into the future.

Why you should oversize solar inverters Perth Solar Warehouse

Oversizing solar inverters simplified.

Forget the equations. You need to know the most you can oversize your particular solar inverter capacity. Below are the most common instances to oversize solar inverters and their maximum input capacity which apply to STCs (Small Technology Certificates) – your subsidy. Here it is simplified:

  • 3 kW Inverter – 3.9 kW Solar.
  • 5 kW Inverter – 6.6 kW Solar.
  • 8 kW Inverter –  10.6 kW Solar.
  • 10 kW Inverter – 13.3 kW Solar.
  • 20 kW Inverter – 26.6 kW Solar.
  • 30 kW Inverter – 39.9 kW Solar.

When network limitations are set by inverter output capacity, oversizing solar inverters are the best way to maximise generation capacity towards overall kWh.

6.6kW of panels on a 5kW inverter explained.

plus 3.9kW of panels on a 3kW inverter.

The most common system combination where oversizing solar inverters occur and to which the reasoning is more so financial than anything else. Residential customers who install greater than 5kW solar inverter capacities will forfeit their ability to qualify for the Synergy solar feed-in tariff (Distributed Energy Buyback Scheme – DEBS). 

Therefore, what’s the best way to achieve greater power production without increasing solar inverter capacity? You guessed it, oversizing solar inverters to the maximum allowable input capacity, 6.6kW.

Additionally, single-phase solar supplies connected to the Western Power network are currently limited to a maximum of 5kW output to mitigate the effects of phase-imbalance.

With a negligible price difference between 3.9kW and 6.6kW solar energy systems due to the way the STC subsidy calculates, there are still scenarios where the preference towards an oversized 3.9kW of solar panels on a 3kW inverter may take preference. 

In areas of stringent grid limitations, preferences for higher-priced product options or rooftops with limited available space for mounting solar arrays can enjoy the benefits of solar energy on a slightly smaller scale.

Related: Installed 6.6kW solar energy system options by Perth Solar Warehouse (with prices). Shop now > 

13.3kW of panels on 10kW inverter explained.

plus 10kW of panels on a 8kW inverter.

Certain network limitations can exist around 3-phase 10kW inverter capacities, enforcing a maximum 10kW output capacity. However, in many instances, the popularity of the 10kW inverter range by most manufacturers ensures an enticing and reduced capital outlay as opposed to selecting a 12 kW or 15kW inverter capacity with virtually the same overall yield.

In many instances, 10kW inverters are less expensive than their 8KW counterparts due to increased demand and the competitive nature of the market.

As the popularity of 13.3kW solar systems on 10kW inverter capacities increase, so does the level of network restrictions. To better negate this, in many residential scenarios, Western Power has begun limiting the maximum inverter capacity to 8kW.

To negate such, a new trend is now emerging with 10kW of solar panels oversized on an 8kW inverter. Unfortunately, due to the cost of the base equipment and the way STC’s are calculated, the price difference between a 10 and 13kw solar energy system is also minimal.

Related: Installed 13kW solar energy system options by Perth Solar Warehouse (with prices). Shop now > 

39.9kW of panels on 30kW inverter explained.

Another excellent example is the export limiting requirements surrounding solar energy systems greater than 30kW on the Western Power network. In this instance, the ability to oversize up to 39kW facilitates a relatively basic grid-tie solar energy system which has the ability to generate almost as much energy as a 40kW system without expensive export limiting features. 

Related: Best value 30kW solar energy systems by Perth Solar Warehouse. Get Quote > 

Bonus offer!

FREE Upgrade on Premium Range Panels. Theres never been a better time for you to to oversize solar inverters with a FREE oversizing upgrade through Perth Solar Warehouse. Get 6.6kW of solar panels for the price of of 5kW or get 13kW of solar panels for the price of 10kW on all premium range solar panel options. 

Mention “OVERSIZE BONUS 2021” prior to buying.

Oversize your solar inverter and harness maximum yields for little to no additional cost. The entire oversized PSW product range is available within the latest PSW digital catalogue for ultimate value.

Get your copy via the above link, and you’ll be guaranteed the best price for your specific installation. It’s that simple.  

Got an additional question in relation to oversizing solar inverters? Ask below at the bottom of this post. – PSW Team.

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