Choosing the right solar system size is one of the most important decisions you will make when going solar. Too small and you will still be paying hefty electricity bills. Too large and you have spent money on panels that will not pay themselves back quickly enough. The good news? For most South Australian homes in the Murray Bridge and Adelaide Hills region, there is a clear path to finding the right size.
At ElectricalPro, we have installed hundreds of solar systems across the region, and the single biggest factor we see in customer satisfaction is getting the system size right from day one. Let us walk you through how to do exactly that.
Step 1
Work Out Your Daily Energy Usage
Your electricity bill holds the key to sizing your solar system correctly.
Grab your most recent SA Power Networks bill (or check your retailer's app) and look for your average daily usage in kilowatt-hours (kWh). This number tells you how much energy your household consumes on an average day.
Here is a rough guide for South Australian homes:
| Household Size | Avg Daily Usage | Quarterly Bill (approx) |
|---|---|---|
| 1-2 people | 8-15 kWh/day | $350-$600 |
| 3-4 people | 15-25 kWh/day | $600-$1,000 |
| 4-5 people | 25-35 kWh/day | $1,000-$1,400 |
| 5+ people or large home | 35-50+ kWh/day | $1,400+ |
Step 2
Match Your Usage to a System Size
Each system size has a sweet spot for different household types.
5kW System
Best for 1-2 person households or retirees. Generates roughly 20-23 kWh/day in Murray Bridge. Ideal if you are home during the day and have modest energy needs. Typically 11 x 475W panels.
6.6kW System
Australia's most popular residential size. Generates 26-31 kWh/day in our region. Suits a 3-4 person family with standard appliances. Around 14 x 475W Jinko or Trina panels.
8-10kW System
For larger families, homes with pools, or heavy air conditioning use. Generates 32-47 kWh/day. Allows for future additions like a battery or EV charger. 17-21 panels.
13kW+ System
Maximum residential size on single-phase power in SA. Generates 52-62 kWh/day. Ideal for large homes, home businesses, or future-proofing with battery storage and EV charging.
These output figures are based on Murray Bridge and Adelaide Hills receiving approximately 4.5 to 5.2 peak sun hours per day (annual average). Your actual output will vary by season — expect around 30% more in summer and 30% less in winter.
Step 3
Consider SA-Specific Factors
South Australia has unique conditions that affect your solar sizing decision.
Feed-in Tariff Rates
SA feed-in tariffs currently sit around 5-8 cents/kWh — a fraction of the 35-45 cents you pay to buy electricity. This means self-consumption is far more valuable than exporting. Size your system to cover your daytime usage first.
Export Limits
SA Power Networks enforces a 5kW export limit on most single-phase connections (10kW for three-phase). Your inverter will be capped regardless of panel capacity. This is why a 6.6kW panel array on a 5kW inverter is so popular — it maximises output without wasting exports.
Peak Sun Hours
Murray Bridge averages 5.0 peak sun hours annually — one of the best in the state. Adelaide Hills areas like Mount Barker and Hahndorf average around 4.5-4.8 hours. More sun means more output per kilowatt installed.
Rising Electricity Costs
SA has some of the highest electricity prices in the world. With prices rising 5-8% annually, a slightly oversized system will become more valuable every year as your avoided costs grow.
Pro Tip
Why Oversizing Slightly is Smart in SA
We often recommend installing 20-30% more panel capacity than your current usage suggests. Here is why:
- Panels degrade by about 0.5% per year — oversizing compensates for this over the 25-year panel warranty
- You may add a battery later (popular options like the Tesla Powerwall 2 need 13.5 kWh to charge daily)
- Electric vehicles are coming — a home EV charger adds 8-15 kWh/day to your usage
- A pool, spa, or future air conditioning upgrade will increase demand
- The cost difference between a 6.6kW and 8kW system is often only $800-1,200 — a payback measured in months, not years
As a real example: a family in Murray Bridge using 22 kWh/day could install a 6.6kW system and cover most of their usage. But for around $1,000 more, an 8kW system would fully cover their current needs and leave room for a future battery storage system or EV charger.
The Maths
How Many Panels Will You Need?
Modern solar panels — like the Jinko Tiger Neo 475W and Trina Vertex S+ 445W panels we install — are significantly more efficient than panels from even five years ago. Here is a quick reference:
| System Size | 475W Panels | 445W Panels | Approx Roof Area |
|---|---|---|---|
| 5kW | 11 panels | 12 panels | ~20 m² |
| 6.6kW | 14 panels | 15 panels | ~26 m² |
| 8kW | 17 panels | 18 panels | ~32 m² |
| 10kW | 22 panels | 23 panels | ~40 m² |
| 13kW | 28 panels | 30 panels | ~52 m² |
Roof orientation matters too. North-facing panels produce the most energy overall in the southern hemisphere. West-facing panels produce more in the afternoon (great if you are home after work). East-facing panels produce more in the morning. Even south-facing panels can work in SA, though they will produce around 15-20% less than north-facing ones.
Shading is the other critical factor. A single shaded panel can drag down the output of an entire string. During your free site assessment, our team checks for shading from trees, chimneys, and neighbouring buildings at different times of day.
Check out our solar and battery packages to see current pricing, or visit our residential solar page for more details on what we install.
FAQ
Common Solar Sizing Questions
Can I add more panels later if I need to?
Yes, but it is more cost-effective to install the right size from the start. Adding panels later may require a new inverter, additional racking, and a second installation visit — all of which add cost. If you are on the fence between two sizes, go larger now.
What size system do I need for a battery?
It depends on the battery capacity. A Tesla Powerwall 2 (13.5 kWh) needs roughly 4-5kW of excess solar generation to charge daily. So if your home uses 20 kWh/day and you want a battery, a 10kW system would cover your usage and charge the battery. We recommend at least an 8kW system for any home planning to add battery storage.
Does the 5kW export limit mean I should only get a 5kW system?
No. The export limit caps what you send to the grid, not what your panels produce. A 6.6kW panel array on a 5kW inverter is the most popular configuration in SA precisely because the panels rarely all produce at peak output simultaneously. The extra capacity means you generate more across the full day, especially in the morning and afternoon shoulders.
How long will a solar system take to pay for itself in Murray Bridge?
Most systems pay for themselves in 3-5 years in the Murray Bridge and Adelaide Hills region, depending on your self-consumption rate. With SA electricity prices among the highest in Australia and our strong solar irradiance (5.0 peak sun hours), payback periods here are shorter than the national average.
Is three-phase power better for solar?
Three-phase allows a 10kW export limit (vs 5kW single-phase) and supports larger systems. If you have three-phase power and are considering 10kW+, it gives you more flexibility. However, for most residential systems under 10kW, single-phase works perfectly well.
Do I need council approval for solar panels in Murray Bridge?
In most cases, no. Solar panel installations on existing residential roofs in the Rural City of Murray Bridge are generally exempt from planning approval under the SA Planning, Development and Infrastructure Act. However, heritage-listed properties and some zone-specific rules may apply. We handle all paperwork and approvals as part of our installation service.