Solar and batteries for large and all-electric homes
Bigger homes, electric cars, heat pumps and pools change the design: more panels, three phase, more storage and backup. Here's how the system scales, and what to check before you sign.
Updated November 2026 · Litmec Electrical, REC-10383
A large Victorian home paying $1,300 a quarter with an electric car, a pool and no gas uses about 60 kWh a day. It suits 15 kW of solar on three phase with a 20 kWh battery or more, saving roughly $3,100–4,250 a year.
The first decision is usually the power supply. On single phase the same all-electric home tops out at about 10 kW of solar. On three phase it can take 13.2 kW, with higher export limits and whole-home backup across all three phases.
How the system scales
| Home | Quarterly bill | Daily use | Solar | Battery | Yearly saving |
|---|---|---|---|---|---|
| All-electric home, single phase (EV, off gas) | $900 | 41 kWh | 10 kW | 20 kWh | $2,450–3,350 |
| All-electric home, three phase (EV, off gas) | $900 | 41 kWh | 13.2 kW | 20 kWh | $2,600–3,550 |
| Large home, three phase (EV, pool, off gas) | $1,300 | 60 kWh | 15 kW | 20 kWh | $3,100–4,250 |
| Very large home, three phase (EV, pool, off gas) | $1,800 | 78 kWh | 15 kW | 20 kWh | $3,550–4,850 |
Two things set large homes apart. Most of the extra use comes from the car, heating and hot water, and much of it can be moved into the middle of the day: charge the car at noon, run the heat-pump hot water on a timer, pre-heat or pre-cool the house. That makes bigger arrays pay. And the evening load is big enough that a battery is almost always worth it.
Where the power goes in an all-electric home
| Load | Typical use per day | Can it run on midday solar? |
|---|---|---|
| Electric car, 12,000 to 20,000 km a year | 6 to 10 kWh | Yes, with a solar-aware charger |
| Ducted reverse-cycle heating in winter | 10 to 30 kWh | Partly, by pre-heating |
| Heat-pump hot water | 2 to 4 kWh | Yes, on a timer |
| Pool pump and heating | 3 to 10 kWh | Yes |
| Induction cooking | 1 to 2 kWh | Mostly evening |
Three phase: often the first decision
Distributors usually cap single-phase homes at about 10 kW of inverter and 5 kW of export. Many large and newer homes already have three phase. If yours doesn't, an upgrade means the distributor runs a new supply, and the switchboard and meter change. It isn't cheap, but it's the only way to fit a 13 to 15 kW system and above in most of Victoria, and it helps fast EV charging and big heat pumps too. Single vs three phase.
Batteries above 20 kWh
Most home batteries are built from modules of about 5 to 16 kWh, and many can be stacked or paired for 20 to 40 kWh. Above about 20 kWh, check three things: whether the inverter can charge and discharge fast enough to use the capacity, where it can be mounted (Australian Standard AS/NZS 5139 restricts locations such as habitable rooms and under stairs), and whether the warranty covers the energy throughput a large home will put through it.
Whole-home backup
Whole-home backup is limited by how much power the inverter can deliver at once (kW), not just how much the battery stores (kWh). Ducted heating, ovens and EV chargers can trip a small inverter, so large homes either back up most circuits and leave the heaviest off, or use a three-phase backup system sized for the whole load. The switchboard needs separating so backed-up circuits switch over automatically. How backup works.
EV charging from solar
About 1.7 kW of panels covers 12,000 km a year of driving. A solar-aware charger charges the car from surplus solar instead of exporting it for a few cents. Single-phase chargers run at about 7 kW; three-phase chargers can run at 11 to 22 kW if the car accepts it. Solar for EV charging.
Designed from your data, not a package
For larger homes, we size the system from how you actually use power, not from a single bill. Your smart meter records use every half hour. Download a year of it from your distributor's customer portal, or send a year of bills, and we design the array, battery and backup around your real load. You get a written design and quote with every component by make and model, the panel layout on your roof, expected output by month, and each rebate on its own line.
What to look for in the quote
- Named equipment, by make and model, for every panel, inverter, battery and backup gateway.
- Inverter power (kW) and battery storage (kWh) listed separately, with what the backup circuit covers.
- Switchboard, three-phase and metering work priced up front, not found on install day.
- The distributor's export limit for your address, and how the design handles it.
- One business responsible for the whole system. With Litmec it's a 5-year whole-of-system warranty on top of the manufacturers' warranties.
Related
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Start with your bill. In step 4, tick what matters most, and add your EV, heating, pool and backup needs to the notes. We'll design from there.
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Questions
How big a solar system can I put on a house in Victoria?
On single phase, distributors usually allow about 10 kW of inverter with exports limited to 5 kW. On three phase, 15 kW and above is common, subject to your distributor's approval for your address. Roof space is the other limit: about 45 m² of usable roof per 10 kW.
Do I need three phase for a big solar system?
For anything much over 10 kW, usually yes. In our model the same all-electric home gets 10 kW on single phase and 13.2 kW on three phase.
How many kWh of battery do I need for whole-home backup?
Usually 15 kWh or more, recharged by solar each day, plus an inverter big enough to run your heaviest loads at once. Most large homes leave EV charging, ovens and some heating off the backup circuit so the battery lasts through an outage.
Is a 20 kWh battery worth it?
For a large all-electric home using 15 kWh or more after dark, often yes, because it has enough evening load to cycle fully most days. For a typical family home it's usually more than needed; 10 to 15 kWh does the job.
Can solar charge my electric car?
Yes. About 1.7 kW of panels covers 12,000 km a year. A solar-aware charger fills the car from surplus solar during the day, which is worth far more than exporting it.
Do you design systems for large homes and new builds?
Yes. Litmec Electrical designs, sells and warrants larger systems across Victoria, including three-phase systems, large batteries and whole-home backup, for existing homes and new builds.
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