How many solar panels you need in Melbourne

How to work out the kW of solar you need

Size solar from the power your home uses, not from the space on the roof. Four steps:

1. Find your daily use. Divide the kWh on your electricity bill by the days in the billing period: 1,800 kWh over 90 days is 20 kWh a day. kWh is energy used over time; kW is a rate, and solar systems are sized in kW. kW and kWh explained
2. Add what you’re planning. An electric car, heating or hot water adds kWh every day, so add it now rather than extend the system later.
3. Divide by what 1 kW makes. In Melbourne a kW of north-facing panels makes about 3.9 kWh on an average day of the year: about 5.2 in summer and 2.5 in winter.
4. Turn kW into panels. Multiply by 1,000 and divide by the panel’s watts. The current panels in our solar panel guide are 435 to 475 W.

Matching your use over the year is the usual starting point. Sizing for winter makes far more than you use in summer, and with no minimum feed-in tariff in Victoria since 1 July 2025, exported solar may earn very little. A battery, or more daytime use, puts that spare solar to work.

What a size saves you

How the sizing calculator works

The calculator at the top of this page turns your daily use into a size. It divides your use, plus anything you’re adding, by what 1 kW of panels makes on your roof direction, using the same PVGIS model as every other page on this site. Then it caps the size at the most panels your supply can take, and counts the panels and their area for every panel in our solar panel guide.

• Over the year or in winter. The year setting makes as much solar as you use on an average day; the winter setting does it on an average June to August day, which takes about 1.6 times the panels.
• Power supply and battery. These set the cap: the inverter your network allows, and how far the panels can exceed it (see the limits below).
• Nearest package. The smallest of our packages at or above your size, for your supply.

It leaves out shade, your roof’s exact pitch, panel ageing and the hour-by-hour timing of your use. Matching your use over a day doesn’t mean solar powers your evenings: for what a size saves, the solar savings calculator splits your solar into what you use and what you export.

Battery size calculator

Panels and roof space by system size

Divide the system’s watts by the panel’s: with today’s 435 to 475 W panels, a 6.6kW system takes 14 to 16 panels. Each of those panels covers about 2.0 to 2.1 m², and the layout needs gaps between rows and clearance from the roof’s edges on top of that.

Higher-wattage panels mean fewer of them, but not much less roof: the panels in our guide make 225 to 238 W per square metre, so the roof area follows the kW more than the panel. The roof sets the upper limit, and the free inspection measures it.

Solar panel sizes and weights

The 5kW solar system

The 10kW solar system

The 15kW solar system

How big can you go on single or three phase?

Your electricity network limits the inverter, not the panels. Every Victorian network pre-approves up to 10 kW of inverter on a single phase home and 30 kW on a three phase home, counting solar and battery inverters together. How far the panels can go past the inverter depends on whether a battery is connected.

Export limits

Networks also cap how much a home can send to the grid, separately from the inverter. The bigger the system, the more often it hits that cap on sunny days, and the more of its output only a battery or daytime use can save. Each network publishes its own rule:

• AusNet Services: 5 kW per phase (15 kW across three phases); 3.5 kW on SWER lines.
• CitiPower: Set at pre-approval; the fixed limit is to fall to 1.5 kW per phase during 2026–31, with flexible exports of up to 10 kW per phase.
• Jemena: 5 kVA per phase (15 kVA across three phases).
• Powercor: Set at pre-approval; the fixed limit is to fall to 1.5 kW per phase during 2026–31, with flexible exports up to the inverter’s capacity (10 kW maximum).
• United Energy: Set at pre-approval; the fixed limit is to fall to 1.5 kW per phase during 2026–31, with flexible exports instead.

On CitiPower, Powercor and United Energy, a large system without a battery could export far less than it makes once the lower fixed limit starts, unless the home takes a flexible export offer.

Single vs three phase power

Export limits and feed-in tariffs

Three phase solar systems

Oversizing: more panels than the inverter

Panels rarely make their full rated power on a roof, so systems usually have more panels than inverter. Under the SAA Technical Requirements (version 1.9, February 2026), a system without a battery needs an inverter of at least 75% of the panels’ peak power: panels up to about 133% of the inverter, which is why a 6.6kW system sits on a 5 kW inverter. With a battery connected, the panels can exceed that ratio, but never the inverter maker’s maximum array size.

What the inverter trims

An inverter can’t put out more than its rating, so on the brightest hours an oversized system loses a little. Capping each hour of PVGIS’s output at the inverter’s rating shows how little at a modest ratio, and how much more at double:

Even at double, the extra panels add output in the mornings, afternoons and winter, when the inverter has room. That is why big single phase systems with a battery go past 133%.

Solar inverters explained

Does roof direction change how many panels you need?

Yes. In Melbourne a north-facing roof makes the most from each panel. East and west roofs make almost as much in summer but much less in winter, so for the same use they need about 15 to 16% more panels over the year, and 45 to 49% more to match a winter day.

A west-facing roof makes more of its solar later in the afternoon, when many homes start using more power, so a slightly bigger west-facing system can still be the better fit. Shade from trees or a second storey cuts output too.

Roof direction, tilt and shade

Output by direction and tilt

Planning for a battery, an EV or an all-electric home

A battery

A battery stores spare daytime solar for the evening, so it needs a system big enough to have some spare. Solar Victoria says most households with only solar panels use around 25% of the energy they generate, and those with a battery around 50 to 60% (source). At 5.1 kW, the example home makes about 26.6 kWh on a summer day against its 20 kWh of use, but only 12.8 kWh in winter, when daytime use comes first and a battery may not fill. Size the solar first, then the battery; a battery also lets the panels pass the 133% ratio.

What size battery you need

An electric car

Work out what the car adds: its kWh per 100 km × the kilometres you drive a day ÷ 100. Add that to your daily use in the calculator. A car that charges at home while the sun is up uses solar directly; one that charges overnight draws from the grid or the battery. SEC Victoria says single phase supports home charging of up to 7.4 kW, so the car alone rarely needs three phase.

An all-electric home

Swapping gas heating, hot water or cooking for electric adds the most use in winter, when solar makes the least, so try the winter setting in the calculator. The Victorian Government’s Power Up Your Home guide says homes don’t need three phase to go all-electric. Your smart meter’s interval data shows when in the day you use power, which sizes solar and a battery better than a bill total.

Download your smart meter data

Building a new home

New Victorian homes are going all-electric. Under planning amendment VC250, new dwellings, apartments and residential subdivisions whose planning permit application was lodged on or after 1 January 2024 can’t have a new gas connection (the amendment’s explanatory report). Most single homes need only a building permit, so that rule doesn’t reach them (AusNet), but from 1 January 2027 every new home must be built all-electric. The Victorian Government announced it in June 2025, and AusNet says the regulations are finalised: a home whose building permit is approved before 31 December 2026 may still be able to connect gas.

Since 1 May 2024, a new Victorian home must also meet the NCC 2022 energy rules: a 7-star NatHERS rating and a whole-of-home yearly energy budget for its heating and cooling, hot water, lighting and pool and spa pumps. Rooftop solar isn’t required, but it can help keep the home under that budget (Australian Building Codes Board; Victoria’s start date). So size the solar for the all-electric home you’ll live in, with the calculator’s winter setting, not just to pass the rating. If the builder’s plans include solar, check its size or get your own quote. Before the plaster goes on, plan:

• Cable routes: conduit from the roof to where the inverter and battery will go.
• Switchboard space for the solar and battery circuits.
• A battery spot that meets AS/NZS 5139:2019, outside the habitable rooms, ceiling spaces and wall cavities it rules out. Where a battery can go

The Solar Homes panel rebate is also available for homes under construction (Solar Victoria): once you’re confirmed eligible, the system must go in within 270 days, against 120 for an existing home. Its current rebate and loan arrangements run to 30 June 2027.

Building now? Ask us when you request a quote whether we can install while your home is being built.

The Solar Homes rebate

Sizes we install

Our packages are complete solar and battery systems: single phase homes choose from 6.6kW, 15kW and 19.8kW, three phase homes from 15kW, 21kW and 28kW. Each output figure comes from the same PVGIS model as the calculator.

We size each home from its bills rather than the number of people in it: two households of the same size can use very different amounts of power.

Packages are starting points: we confirm the size for your roof, your bills and your switchboard at the free inspection.

Compare the packages

The 6.6kW system in detail

Sizing your solar: your questions