Solar sizing guide
How to Size a Solar System for Your Ballarat Home
Too small and you keep paying big power bills. Too big and you pay for panels you don’t need. Use this guide and our free calculator to work out the right solar system size for your home in Ballarat and surrounding areas.
The quick answer
To size a solar system in Ballarat, divide your average daily electricity use (kWh) by 3.2. The result is the system size in kilowatts (kW) you need to match your usage.
Daily kWh ÷ 3.2 = system size in kW
Example: 20 kWh a day ÷ 3.2 = 6.25 kW, so a 6.6 kW system (15 panels) is the right fit.
Why 3.2? Ballarat averages about 4 peak sun hours a day across the year, and a typical system delivers about 80% of its rated output once heat, wiring and inverter losses are counted. 4 × 0.8 = 3.2 kWh per kW, per day.
Most Ballarat homes end up with a 6.6 kW to 10 kW system. The steps below show how to find your own number.
How to size your solar system in 5 steps
Step 1. Find your daily electricity use
Grab your latest power bill and find the total kWh used, then divide by the number of days in the billing period.
Example: 1,800 kWh over 91 days = 19.8 kWh per day.
Look at a winter bill and a summer bill if you can. Ballarat homes with electric heating often use twice as much in July as they do in January. You can also download half-hourly data from your retailer’s app or the Powercor online portal to see exactly when you use power.
| Household | Typical daily use |
|---|---|
| 1–2 people | 8–12 kWh |
| 3–4 people | 15–22 kWh |
| 5+ people or all-electric home | 25–35+ kWh |
Step 2. Allow for Ballarat's sunshine
Ballarat sits higher and further south than Melbourne, so winter days are short and often cloudy. A solar system here produces about three times more on a clear summer day than in mid-winter. These are approximate average peak sun hours by season:
Summer – about 6.2 hours
Spring – about 4.6 hours
Autumn – about 3.4 hours
Winter – about 2.0 hours
We size systems on the yearly average of about 4 hours. If winter bills worry you most, size up rather than down.
Step 3. Do the maths
Divide your daily use by 3.2, then round up to the nearest whole number of panels.
19.8 kWh ÷ 3.2 = 6.2 kW
6,200 W ÷ 440 W panels = 14.1, rounded up to 15 panels
15 × 440 W = 6.6 kW system
Most panels installed today are 420–475 W. Higher-wattage panels mean fewer panels and less roof space for the same system size.
Step 4. Plan for the next 5–10 years
Your usage today is only half the story. Add these to your daily figure if they’re on your list:
| Future change | Allow roughly |
|---|---|
| Home battery | 30% bigger system |
| Electric vehicle (about 12,000 km a year) | +6 kWh a day |
| Gas to electric (heat pump hot water, split systems, induction) | +5 kWh a day |
Adding panels later usually costs more than installing the right size first, because matching panels and spare inverter capacity are hard to find years down the track.
Step 5. Check your roof and grid connection
Roof space: each panel needs about 2 m². A 6.6 kW system takes around 30 m² of usable, unshaded roof.
Inverter size: your panels can be up to 133% of the inverter’s rating and still qualify for the federal STC rebate. That’s why a 6.6 kW array is commonly paired with a 5 kW inverter.
Export limits: Ballarat is on the Powercor network. Single-phase homes usually have a limit on how much solar they can send back to the grid, so larger systems may need export limiting. Three-phase homes have more flexibility. We check this for you before quoting.
Solar system size calculator
Solar size calculator for Ballarat homes
Enter your usage and see the system size that suits your household, plus what it will produce in summer and winter.
Summer day: 33 kWh
Winter day: 11 kWh
This is a guide only. It assumes a north-facing roof with little shade, 4 average peak sun hours a day and typical system losses. Your installer should confirm the final design with a site inspection.
Solar size chart for Ballarat homes
Find your daily usage in the left column to see the system size, panel count and expected output.
| Daily use | System size | Panels (440 W) | Summer day | Winter day |
|---|---|---|---|---|
| 10 kWh | 3.5 kW | 8 | 17 kWh | 6 kWh |
| 15 kWh | 4.8 kW | 11 | 24 kWh | 8 kWh |
| 20 kWh | 6.6 kW (most popular) | 15 | 33 kWh | 11 kWh |
| 25 kWh | 7.9 kW | 18 | 39 kWh | 13 kWh |
| 30 kWh | 9.7 kW | 22 | 48 kWh | 15 kWh |
| 40 kWh | 12.8 kW | 29 | 63 kWh | 20 kWh |
Estimates assume a north-facing roof with little shade. Systems over about 6.6 kW on single-phase power may need export limiting.
Sizing examples for Ballarat homes
Here’s how the sizing steps work out for three typical local households.
Retired couple in Wendouree
12 kWh a day, home most of the day. 12 ÷ 3.2 = 3.75 kW, so a 4 kW system (9 panels) with a 3 kW inverter.
Family of four in Alfredton, adding a battery
18 kWh a day. 18 ÷ 3.2 = 5.6 kW, plus 30% for the battery, so a 7.5 kW system (17 panels) with a 6 kW inverter.
All-electric home in Buninyong with an EV
22 kWh a day plus 6 kWh for the car = 28 kWh. 28 ÷ 3.2 = 8.75 kW, so an 8.8 kW system (20 panels). On single-phase power this needs export limiting.
Examples are illustrative and assume a north-facing roof with little shade.
What else affects the size you need
Roof direction
North-facing panels produce the most. East and west roofs produce a little less in total but spread output across the morning and afternoon, which can suit families who are home early and late. Add one or two extra panels to make up the difference.
Shade from trees and buildings
Ballarat’s established gums and elms can shade roofs in winter when the sun is low. Even partial shade cuts output, so we use micro-inverters or optimisers on shaded sections and adjust the system size to suit.
When you use power
Solar saves the most when you use it as it’s generated. If you’re out all day, run the dishwasher, washing machine and hot water on a timer during sunny hours, or consider a battery to store the excess.
Feed-in tariffs
Feed-in tariffs in Victoria are now low, so exporting lots of power earns little. The best value comes from a system matched to your own use, rather than the biggest system your roof can hold.
Solar sizing FAQs
What size solar system do I need for my Ballarat home?
Divide your average daily electricity use in kWh by 3.2. That figure is about what each kilowatt of solar produces per day in Ballarat on average. A home using 20 kWh a day needs roughly a 6.6 kW system.
Is a 6.6 kW solar system enough?
A 6.6 kW system suits most Ballarat homes using 15 to 22 kWh a day. It produces around 7,700 kWh a year, but output drops to roughly 10 to 11 kWh a day in mid-winter, so larger households or homes planning a battery or EV often go bigger.
How many solar panels do I need?
Divide your system size in watts by the panel wattage. With 440 W panels, a 6.6 kW system needs 15 panels, a 10 kW system needs 23 panels, and a 13.2 kW system needs 30 panels.
Do I need a bigger solar system if I add a battery?
Usually yes. The panels need to cover your daytime use and charge the battery, so a system around 30% larger than usage alone suggests is a sensible starting point.
Does Ballarat's cold weather reduce solar output?
Cold temperatures actually help panels run more efficiently. What lowers winter output in Ballarat is shorter days, a lower sun angle and more cloud, which is why winter production is about a third of summer production.
Can I add more panels later?
It is possible but often costs more than sizing correctly at the start, because matching panels and spare inverter capacity can be hard to find later. If you expect your usage to grow, it is usually cheaper to install the larger system upfront.
Get your system sized by a local expert
Send us a recent power bill and your address. We’ll check your roof, shading and Powercor connection, then recommend the right system size with a free, no-obligation quote.
