What solar and battery system suits your home?
Six quick questions give you a straight answer: panel size, inverter, battery and backup, and what it could save. Then, if you like it, we'll design it for your roof.
Updated November 2026 · Litmec Electrical, REC-10383
Most Victorian homes paying $300 to $600 a quarter suit about 6.6 kW of solar (around 15 panels), which makes about 9,500 kWh a year on a north-facing Melbourne roof. Homes with an electric car, a pool or no gas suit 10 kW on single phase, or 13 to 15 kW on three phase.
A battery pays when you use more than about 4.5 kWh after dark each day. Size it to about 80% of your evening use, usually 10 to 15 kWh for a family home. Backup in a blackout is a separate choice: it changes the inverter and the switchboard wiring, not just the battery.
The system that suits each kind of household
System size follows how much power you use and when you use it, not how big the house is. These are the systems our calculator recommends for common Victorian households. Find the row closest to yours, or use the finder above for your own answers.
| Household | Quarterly bill | Daily use | Solar | Battery | Yearly saving |
|---|---|---|---|---|---|
| Couple, both out at work (nothing extra) | $300 | 7 kWh | 6.6 kW (~15 panels) | 5 kWh | $650–900 |
| Small family (nothing extra) | $450 | 13 kWh | 6.6 kW (~15 panels) | 10 kWh | $1,000–1,400 |
| Family, someone home most days (nothing extra) | $650 | 20 kWh | 6.6 kW (~15 panels) | 10 kWh | $1,400–1,950 |
| Family with an electric car (EV) | $650 | 26 kWh | 10 kW (~23 panels) | 15 kWh | $1,800–2,500 |
| All-electric home with an EV (EV, off gas, three phase) | $900 | 41 kWh | 13.2 kW (~30 panels) | 20 kWh | $2,600–3,550 |
| Large home: EV, pool, no gas (EV, pool, off gas, three phase) | $1,300 | 60 kWh | 15 kW (~34 panels) | 20 kWh | $3,100–4,250 |
Three things stand out. Below about $300 a quarter, most of the bill is the daily supply charge, which solar can't touch. Being home in the day matters as much as the size of the bill, because solar you use yourself is worth about 30c per kWh and solar you export earns a few cents. And an electric car or moving off gas changes the answer more than anything else: those homes need more panels and get the most from a battery.
1. Panels: how much solar
Start from your daily use. Divide your bill's usage by the days in the bill, or let the finder do it from the dollar figure. Each kW of panels makes about 3.5 kWh a day averaged over a Victorian year, and about 3.9 on an ideal north-facing roof. A good rule: solar size in kW ≈ daily use ÷ 3.5, plus 10%, and no less than 6.6 kW, because the extra panels cost little next to the fixed costs of an install.
- 6.6 kW (about 15 panels) suits most homes using up to about 20 kWh a day.
- 8 to 10 kW (18 to 23 panels) suits families using 20 to 30 kWh a day, or anyone adding an electric car.
- 13.2 to 15 kW (30 to 34 panels) suits all-electric homes and large homes, and needs three phase in most of Victoria.
Single-phase homes are usually limited to about 10 kW of inverter and 5 kW of export by the electricity distributor. More on single vs three phase. Roof space can be the real limit: each 440 W panel is about 2 m², so 10 kW needs about 45 m² of usable roof. East and west faces work well: they make about 85% of a north face and spread output across the day (east-west solar).
2. Inverter: string, micro or hybrid
- String inverter: one box on the wall. Simplest and best value on an unshaded roof with one or two faces.
- Microinverters or optimisers: electronics behind each panel. Worth it on shaded roofs or roofs with three or more faces, and they show each panel's output in the app.
- Hybrid inverter: runs the panels and a battery from one unit. Choose it if you want a battery now, or are likely to add one in the next few years.
- Three-phase inverter: for three-phase homes with larger systems. It spreads output across all three phases and allows higher export limits.
3. Battery: yes, not yet, or no
- Yes if you use more than about 4.5 kWh after dark, have a bill over about $400 a quarter, or are adding an electric car or electric heating. Size it to about 80% of your evening use: usually 10 to 15 kWh for a family, 20 kWh or more for large all-electric homes.
- Not yet if your evening use is small. Fit a battery-ready (hybrid) inverter now and add the battery when prices fall or your use grows.
- Yes, for backup if outages are common where you are, you rely on a pump or medical equipment, or you simply want the lights on in a storm. Backup is about resilience more than payback.
Batteries rarely fill on short winter days, and every kWh stored loses about 10% on the way in and out. Our numbers allow for both. Is a battery worth it? goes through the maths.
4. Backup: essentials or the whole home
Standard solar switches off in a blackout, even in full sun. A battery with a backup-capable inverter keeps chosen circuits running. Essential circuits (fridge, freezer, lights, internet, a water pump) need about 3 to 8 kWh a day and suit a 10 kWh battery or larger. Whole-home backup needs a bigger inverter, usually 15 kWh of storage or more, and a switchboard set up for automatic changeover. How battery backup works.
5. Quality: what separates a premium system
- Panels on the Clean Energy Council approved list, with a product warranty of 25 years or more, not just a performance warranty. High-efficiency panels when roof space is tight.
- Inverter and battery from manufacturers with an Australian office that honours the warranty, and a battery warranty that states both years and energy throughput.
- Design from your own bills and roof: panel layout drawn to your roof faces and shading, not a standard package.
- Installation by accredited installers, with tidy conduit, correct isolators and a switchboard checked before you sign. The switchboard is where most solar jobs get held up. Check yours.
- One business responsible for the whole system. With Litmec, your contract and the 5-year whole-of-system warranty are with us, on top of the manufacturers' warranties.
Get it designed for your roof
The finder and the table use averages. Your roof's direction, shading, switchboard and tariff decide the final design. Send us your details below and Litmec Electrical, a registered electrical contractor since 2007, will design the system for your home. You get a written quote listing every panel, inverter and battery by make and model, with each rebate on its own line. Site visits are free within about 100 km of Newport. Anywhere else in Victoria, we start with a free assessment from your bills and roof photos.
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Questions
What size solar system do I need?
Divide your daily power use by about 3.5 and add 10%. Most homes paying $300 to $600 a quarter use 10 to 20 kWh a day and suit 6.6 kW. A family with an electric car paying $650 a quarter suits about 10 kW, and a large all-electric home on three phase suits 15 kW.
What size solar system do I need for a 4-bedroom house?
It depends on use, not bedrooms. A typical 4-bedroom family home in Victoria using 20 to 30 kWh a day suits 8 to 10 kW. With an electric car, a pool or ducted electric heating, 10 kW on single phase or 13 to 15 kW on three phase is common.
How many solar panels do I need?
At about 440 W per panel, 6.6 kW is about 15 panels, 10 kW about 23, and 13.2 kW about 30. Each panel takes about 2 m² of roof.
Do I need a battery with solar?
Only if you use enough power after dark, roughly 4.5 kWh or more a day, or want backup in a blackout. Otherwise start with solar on a battery-ready inverter and add a battery later.
What size battery do I need?
Size it to about 80% of your evening use. A small family suits about 10 kWh, a family home in the day most days about 10 kWh, and a large all-electric home 20 kWh or more. Whole-home backup usually needs 15 kWh or more.
Is 10 kW of solar too much?
Not if you use it. Extra panels cost little, but exported power earns only a few cents per kWh in Victoria, so 10 kW pays best for homes using 20 kWh a day or more, or planning an electric car or moving off gas. Single-phase homes are usually capped at about 10 kW of inverter.
Should I choose microinverters or a string inverter?
A string inverter suits an unshaded roof with one or two faces. Microinverters or optimisers suit shaded roofs or roofs with three or more faces, and show each panel's output. A hybrid inverter suits anyone adding a battery now or later.
Can Litmec design and install the system the finder recommends?
Yes. Litmec Electrical designs the system for your roof, gives you a written quote, organises the rebates and network approval, and warrants the whole system for 5 years. Accredited installers we subcontract and supervise fit the panels, and our own electricians do any switchboard work.
Check it on your roof
One minute online, then a free visit from a licensed electrician who checks your roof and switchboard.