Case Study: 13kW Residential Solar System - Goliath Solar & Electrical

Case Study: 13kW Residential Solar System

In this blog we’ll dig into the current trends we are seeing in size selection for residential solar systems and offer some insights into the key learnings from our 13kW Case Study.

System Sizes Compared

In our recent blog What Size Solar System Do I Need? we discuss in depth the most important considerations for making your size choice including:

• Your budget. 

• How much energy your household uses.

• How soon do you want to see the return on your investment?

• Current Rebates and changes to Rebates in the future.

Recent Trends 

Between 2016 – 2018 the top residential solar system sizes being installed were: 3kW, 5kW and 6.6kW.

Interestingly, from 2019 – 2021 we are seeing a trend for most installs being slightly larger at: 7.875kW, 10.71kW and 13.23kW.

Why Bigger Systems Are Popular Now

So the obvious question is: Why all of a sudden are we seeing more interest in installing these larger 7.875kW, 10.71kW and 13.23kW systems? 

The top reason from our perspective is that more people are going into solar with the aim of future proofing a future battery install, and alongside the epic power prices we are currently paying, people are realising that more panels will quite simply serve them better in the years ahead. 

As batteries costs are unfortunately currently still too high even with the government rebate, (read Our Guide To The Home Battery Scheme), many consumers are waiting for battery costs to fall further before investing in a home battery. 

So the economic sense currently is to install as much solar as you can to match your future battery size. Now in terms of battery storage – Tesla can store 13.5kWh and LG can store 8.8kWh, so with these batteries you want to make sure you generate enough electricity to power your home AND charge your battery daily.

Average Energy Production in Summer

In Adelaide we all know it’s not all sunshine and our winters can be dark, cold and wet! So we know in summer your solar system will generate more than enough electricity to power your home, air con and enough to charge battery during sunlight hours. In fact the average daily summer production rates are as follows:

6.615kW = 30kWh daily average

7.875kW = 35kWh daily average

10.71kW = 50kWh daily average

13.23kW= 60kWh daily average

Average Energy Production in Winter

Now here lie the design constraints and why we look to install as many panels that can fit on your roof within budget and the likelihood of adding batteries later. What about winter which represents ¼ of the year performance?! Well let’s look at your daily average rates of energy production in the cooler months now: 

6.615kW = 14kWh daily average

7.875kW = 17kWh daily average

10.71kW = 22kWh daily average

13.23kW= 30kWh daily average

So as you can see in the winter season for instance, having a 6.615kW system would be disappointing, only producing enough electricity from your solar panels 50% of the time to fully charge it and having to rely on the expensive grid all day for electricity. Perhaps an LG Chem would be better suited than a Tesla in this instance.

Our current recommendation is that now is the time to install, take advantage of the current Feed-In Tariffs, and then simply add a battery once the starting prices have dropped. This thinking is contributing to the growth in popularity of the larger 7.875kW, 10.71kW and 13.23kW systems in SA. 

Key Learnings From Our 13kW Case Study

– We are seeing a conservative $3,614 yearly savings at the current electricity rates (35c per kWh) and feed in tariff (15c per kWh) for our clients.

– The 13kW solar system is a great system for those looking to add a battery later down the track. This is because it allows for more production during the cooler months to charge a future battery when added. See our Tesla Battery Fact Sheet for details.

– Even if the Feed In Tariff was to drop by say 40% and go down to 10c per kWh exported in the future, which we see happening, average savings will still be between $2,750 and $3,250 a year! This is still a 20% return on investment and an under 5 year payback.

I encourage you to read through our real life case study for a 13kW system based on 12 months real data for an average family!

Even better check out a link to a live 13kW Fronius/Canadian solar system installed


13kW Case Study – Future Proof System Size 2020
Currently most popular due to households opting to prepare for future battery installs. 

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