For many homeowners, the size of the solar system and the cost go hand in hand. They are big contributing factors in the decision making.
Prevalent marketing boasts large solar systems for ‘bargain’ prices. But what is that system actually going to do for you?
Do you actually need a large system, or is that just what you are being told you need?
Are you buying it because the price is ‘too good to be true’ and you think you’re getting ‘more bang for your buck’, or is it the right size for you, that will get you the return on investment you are expecting?
The most important thing to be aware of when investing in solar is Export Limits.
- Export is the energy produced by the solar power system that is not consumed by the home. This energy is sent back to the grid and a credit per kW is applied to your power bill. This helps to offset nighttime usage when the solar is not producing.
- Any system with an inverter size over 5kW has an export limit imposed by Ergon.
- This limit is a maximum of 5kW/hr.
- When a system reaches the maximum export limit, no further solar production is generated as this excess power has nowhere to go.
This means, once your system is exporting 5kW/hour back to Ergon, the inverter will not continue to produce any further energy unless your household load increases.
The below examples show real data from a 13kW system. This homeowner’s average summer bill is around $1500/quarter. The system has 2 x Fronius Inverters, which have the capacity to produce 13.2kW of power.
Example 1 – Peak Production
The blue line shows the household line, while the yellow section indicates the solar power they consumed directly; around 5kW for most of the day. The inverter peaks production at 10kW (the grey section).
The quality of these panels means the peak production is only for a very minimal timeframe. High quality panels will provide higher production for a longer duration. While the export limit is capped at 5kW/hr, this would still allow for the maximum to be exported for a longer period of time.
Unfortunately for this homeowner, the panels installed are of a lower quality, and therefore, reach the maximum production for a very brief part of the day.
With the system peaking at 10kW, and exporting the maximum back to the grid, there is an entire 3kW of panels being unused on the roof.
Example 2 – Export Limited
This shows how the power being consumed in the house has directly impacted the system production due to the export limit.
With low consumption, the inverter exports the maximum 5kW back to the grid. As there is no use for any additional power, the system simply does not produce any more.
As the household load increases, so too does the total production.
However, again, it does not go over 10kW production due to only 5kW being consumed within the home at the time.
Example 3 – Oversized System
This is what the system does for 6 months of the year, when the homeowner isn’t running their AC’s regularly and drawing on a lot of energy.
Constant limiting of the system with the 5kW export limit, due to the low consumption in the home and no need for excess energy. In these months, the system doesn’t reach higher than 8kW peak production.
So there is 5kW of solar panels on the roof doing nothing. That’s an entire solar system!
Of course, if you are a particularly high energy user, a system this size might just be perfect for you. If you find yourself with astronomical power bills and running high loads during day light hours, then a larger system is probably recommended to lower your bills.
But if you’re not home during the day to use the power, remember the export limit is going to restrict the amount your system produces.
What good is a huge system on your roof if most of it's not doing anything for you?
If you are interested in a full battery system, then a larger system might be suitable. This way, that excess ‘potential’ energy can charge the battery before it is exported, allowing the system to reach higher production values and therefore, utilise its full capacity.
With a battery system, there would be less wasted panels on the roof and more benefit to you.
This is something to consider and speak with your solar professional if you are unsure. The system you choose should be tailored to your individual household needs, not just another ‘cheap’ system sold to you because the ‘bigger the better’.
You might pay the same amount for a smaller system, but the benefit is likely to be greater. Not to mention the quality of products, and therefore better overall solar production.