It’s one of the first questions almost every Melbourne homeowner asks when they start looking into solar: how many panels do I actually need? The honest answer is that it depends — but there’s a straightforward way to think through it, and getting the sizing right from the start makes a significant difference to the return on your investment.
Here’s what you need to know.
Start With Your Electricity Usage
The most important factor in determining how many solar panels you need is how much electricity your household currently uses. This is measured in kilowatt-hours (kWh) and is shown on your electricity bill.
Daily usage varies a lot from home to home, depending on the number of occupants, whether you have a pool, air conditioning, an EV, electric hot water, and so on. Broadly speaking, a smaller household with modest energy use will need a smaller system, while a larger household — or one with higher energy demands — will get more value from a bigger one. There’s no single “right” system size that applies across the board, which is why the same house next door might end up with a completely different recommendation to yours.
The only way to know what’s right for your home is to look at your actual usage pattern, which is exactly what a proper solar assessment is for.
Popular System Sizes in Melbourne
Residential solar systems in Melbourne span a wide range, from smaller setups suited to modest households through to larger systems for bigger homes or higher energy use. Within that range, certain sizes tend to come up more often than others simply because they suit how a standard single-phase home connection is set up, and because of how inverters and panel arrays pair together efficiently under Australian standards.
Rather than fixating on a specific number, it’s more useful to think of system size as a range that gets narrowed down once your usage, roof, and goals are on the table.
What Affects How Much a Solar System Actually Produces?
Two homes with identical systems can produce quite different amounts of electricity. The key variables are:
Roof orientation:
A north-facing roof is ideal in Australia, as it receives the most direct sunlight throughout the day. East and west-facing roofs still work well. South-facing roofs produce significantly less and are generally not recommended for solar unless no other option exists.
Roof pitch:
A pitch of around 20–30 degrees is close to ideal for Melbourne’s latitude. Most standard suburban rooflines fall within an acceptable range.
Shading:
Trees, neighbouring buildings, chimneys, and even satellite dishes can cast shadows that reduce output. Modern microinverters or DC optimisers can minimise the impact of partial shading, but significant shading is worth addressing before installing.
Panel quality:
Higher-quality panels with better efficiency ratings generate more electricity from the same surface area. This matters particularly if your roof space is limited.
Melbourne’s climate:
Melbourne gets around 4.2 peak sun hours per day on average — slightly less than sunnier cities like Brisbane or Perth, but more than enough to make solar highly viable. Factor in Melbourne’s variable weather and the rule of thumb is to size slightly more generously than you might in Queensland.
Should You Add a Battery?
If your household uses most of its electricity in the morning and evening (as most working households do), you may find that a solar-only system generates more than you can use during the day and earns you relatively little for the excess exported to the grid. A battery changes that equation significantly — storing your daytime generation for use in the evening peak, when grid electricity is at its most expensive.
Whether a battery makes financial sense depends on your usage patterns, how much you export, and your current electricity tariff. It’s worth discussing with your installer.
How to Get the Sizing Right
The most reliable way to determine the right system size for your home is to have a qualified solar installer review your last 12 months of electricity bills, assess your roof, and model your expected generation and savings. There’s genuinely no substitute for this step — general guidance can point you in the right direction, but your bill and your roof are what determine the final recommendation.
A good installer will also factor in any planned changes to your energy use — such as an upcoming EV purchase, a hot water system upgrade, or a growing family — so your system is sized not just for today, but for the next decade.
Thinking about going solar but not sure where to start? O'Brien Electrical & Plumbing Rowville’s solar experts can assess your home, recommend the right system size, and handle the full installation from start to finish. Call us on (03) 8520 9555