What Size Solar System Do I Need for My Australian Home?

Published 22 January 2026

The most common solar sizing question Australian households ask is: how many kilowatts do I actually need? The answer depends on your daily electricity usage, how much of that usage falls during daylight hours, your roof space, and your budget. This guide walks through how to work it out.

Step 1: Find your daily electricity usage

Your electricity bill shows your usage in kWh. Most bills show a daily average 鈥?look for a figure like "18.5 kWh/day" or a total quarterly usage that you can divide by the number of days.

Typical Australian household daily usage:

If you have a smart meter, your retailer's app may show your daily or half-hourly usage 鈥?this is more accurate than a bill average.

Step 2: Understand what a solar system actually generates

A solar system's output varies by location, season, roof angle and shading. In Australia, a commonly used estimate is the "peak sun hours" concept 鈥?the equivalent number of hours per day the sun shines at full rated intensity.

Approximate daily generation per kW of installed solar capacity:

A 6.6kW system in Sydney generates approximately 6.6 脳 4.0 = 26kWh per day on average, though this varies significantly between summer and winter.

Step 3: Match system size to your self-consumption

There are two ways to size a solar system:

Size to your daytime usage: Install a system that roughly covers what you use during daylight hours. If you use 10kWh between 9am and 5pm, a 4鈥?kW system may cover most of that.

Size to your total daily usage (with future battery in mind): If you plan to add a battery later, a larger system that generates surplus for storage makes sense. If you have an EV or plan to get one, factor in the additional charging load.

In 2026, with panel costs lower than ever and feed-in tariffs low, oversizing your system tends to be a better financial decision than undersizing. A system that generates 30kWh when you use 20kWh is more valuable than one that generates 15kWh 鈥?even if the extra 10kWh is exported at $0.06/kWh, the cost difference between a 5kW and 7kW system is often small.

What 6.6kW means in practice

Most Australian installers default to 6.6kW because it is the maximum system size that can use a standard 5kW inverter (inverters can be loaded at up to 133% of their rated capacity). A 6.6kW system with a 5kW inverter is the most common configuration.

For a household using 20kWh per day in Sydney:

• A 6.6kW system generates ~26kWh/day on average
• Self-consumption during solar hours might be 10鈥?2kWh
• Roughly 14kWh is exported at the feed-in tariff rate
• Adding a 10鈥?3.5kWh battery would capture most of that export for evening use

When to consider a larger system (10kW+)

A system above 6.6kW makes sense if:

• You have an EV and want to charge primarily from solar during the day
• You have a pool with a large pump
• You have a large household with high daytime usage
• You are considering a battery and want to fill it fully most days
• Your network allows export at higher levels (some networks cap export 鈥?check before sizing up)

Roof space requirements

As a rough guide:

• 1kW of solar panels requires approximately 4鈥?m虏 of usable roof space
• A 6.6kW system requires approximately 26鈥?0m虏
• A 10kW system requires approximately 40鈥?0m虏

Panel orientation and shading matter. North-facing panels in Australia generate the most energy. East and west-facing panels generate less but spread generation across more of the day. South-facing panels are generally avoided unless no other option exists.

Questions to ask your installer about sizing

• What is the annual generation estimate for this system at my address?
• What is my estimated self-consumption percentage?
• What is the export limit for my network connection?
• How would the system size change if I add an EV or battery in the next 3 years?
• What inverter size are you quoting, and why?