How to Size a Solar System for Your Adelaide Home
Most Adelaide homes need between 6.6kW and 13.2kW of solar. To find your number, divide your average daily electricity use by 4.2, then adjust for three things: whether you’re adding a battery, when your household uses power, and what your SA Power Networks connection allows.
The Quick Formula
1kW of solar panels in Adelaide produces about 4.2 kWh a day averaged over the year, according to the Australian Government’s energy.gov.au figures. Summer days produce well above that and winter days well below it. That single number is the basis for every sizing decision:
Solar size (kW) = daily use (kWh) × 1.1 ÷ 4.2
Planning a battery? Use × 1.5 instead of × 1.1.
The multiplier covers winter, when output drops sharply, and gives a battery enough surplus to fill up. Here’s what common system sizes look like on an Adelaide roof:
| Panels | Typical inverter | Avg daily output | Usually suits |
|---|---|---|---|
| 6.6kW (15 panels) | 5kW | ~28 kWh | Up to ~20 kWh/day, no battery |
| 8.8kW (20 panels) | 6–8kW | ~37 kWh | 20–30 kWh/day, or a small battery |
| 10.6kW (24 panels) | 8kW | ~44 kWh | Larger families, or solar + battery |
| 13.2kW (30 panels) | 10kW | ~55 kWh | The single-phase maximum; high use + battery |
| 17.6kW+ (40+ panels) | 15kW+ | ~74 kWh+ | Three-phase homes with an EV, pool or both |
Based on 440W panels, a north-facing roof with little shade, and 4.2 kWh per kW per day. East–west roofs produce slightly less in total but spread generation across the day.
Prefer not to do the maths? Our solar calculator works it out from your bill.
Want Your Own Number in a Minute?
Our solar calculator runs this formula for you. Enter the figures from your bill and it suggests a system size and estimates what it would save you.
Sizing Your System in Five Steps
This is the same process our designers follow before they quote, so you can check any quote you receive against it, or let our solar calculator do steps 1 and 3 for you.
1. Work out your daily use from your bill
Find the total kWh on your latest bill and divide by the days in the billing period. A bill showing 1,820 kWh over 91 days means you use 20 kWh a day. If you can, check a summer and a winter bill, because ducted air conditioning or electric heating can swing usage by 50% or more between seasons. Size for the higher of the two if a battery is part of the plan.
2. Look at when you use it
Solar only saves you money on power you use while it’s generating, or store in a battery. Power you send to the grid earns a feed-in tariff of just a few cents per kWh with most SA retailers, while power you buy costs many times more. A household that’s home during the day, or can run the dishwasher, pool pump and hot water between 10am and 3pm, gets far more from the same panels than one that’s empty until 6pm.
3. Apply Adelaide’s sunshine figure
Divide your daily use by 4.2 to get the kW that matches your use on an average day. Then add headroom. Winter output in Adelaide is often less than half of a clear January day, and panels lose a little output each year. That’s why we multiply by 1.1 without a battery and 1.5 with one.
4. Check what your SAPN connection allows
SA Power Networks sets the ceiling for every Adelaide install:
- Single-phase homes can have up to 10kW of inverter capacity in total, including any battery inverter.
- Three-phase homes can have up to 30kW (10kW per phase).
- Panels can exceed the inverter by up to 33% and still earn the federal solar rebate, so a 10kW inverter can carry about 13.3kW of panels.
- Exports are either flexible, up to 10kW per phase but reduced by SAPN when the local network is congested, or fixed at 1.5kW per phase. Most new systems go flexible.
If your usage points to more than 13.3kW and you’re on single-phase, a three-phase upgrade can be worth pricing. Otherwise, a battery helps you use more of what a single-phase system produces.
5. Decide on a battery now, or leave room for one
If a battery is likely in the next few years, choose a hybrid inverter and size the panels for it today. Adding panels later often means a second inverter, a second SAPN application and panels that don’t match. For batteries themselves, the federal battery rebate pays its full rate only on the first 14 kWh of usable capacity, so most Adelaide homes get the best value from something in the 10–14 kWh range.
Three Adelaide Homes, Three Different Answers
Two homes with the same bill can need different systems. These examples are typical of the households we design for.
Working couple, Marion
1,460 kWh per quarter, so about 16 kWh a day, mostly after 5pm. Single-phase, no battery yet.
Recommendation: 6.6kW of panels on a 5kW hybrid-ready inverter, generating about 28 kWh a day.
The formula says 4.2kW, but the extra panels cost little, carry them through winter and leave surplus for a battery once they add one.
Family of five, Golden Grove
3,640 kWh per quarter, so about 40 kWh a day, with ducted air conditioning and a pool pump. Single-phase, battery now.
Recommendation: 13.2kW of panels on a 10kW hybrid inverter, the single-phase maximum, with a battery of around 13 kWh.
The formula says 14.3kW, so this home hits the SAPN ceiling. Moving the pool pump into the middle of the day and keeping the battery inside the full-rebate band gets the most out of what single-phase allows.
Three-phase home with an EV, Mawson Lakes
3,300 kWh per quarter (about 36 kWh a day) plus an EV adding about 8 kWh a day, so 44 kWh a day. Three-phase.
Recommendation: 15.8kW of panels on a 15kW three-phase hybrid inverter, averaging about 66 kWh a day, plus a battery of around 14 kWh.
The EV charges from 10am to 3pm on weekends and days at home, which is the cheapest power this household can get.
What's Changed in 2026
Battery rebate tiers (from 1 May 2026). The federal Cheaper Home Batteries Program now pays the full rate on the first 14 kWh of usable capacity, 60% from 14 to 28 kWh and 15% from 28 to 50 kWh. The rate also steps down every six months. Oversized batteries are much worse value than they were a year ago.
Solar Sharer free power (from 1 July 2026). SA retailers must now offer an opt-in plan with free electricity from 12pm to 3pm. If you have solar, you’re already covering most of that window, so it changes which electricity plan suits you more than the size of your system.
The solar rebate keeps shrinking. The number of certificates (STCs) a new solar system earns drops every 1 January until the scheme ends in 2030. Buying the right size once is cheaper than adding panels later at a lower rebate.
Rebate settings can change. We confirm the current rules for your installation date when we quote.
Sizing Mistakes We See on Adelaide Roofs
Sizing to cover the whole bill. With low feed-in tariffs, a system that exports most of its output pays back slowly. Match the system to what you use, then add storage if you want more independence.
Sizing for summer. A system that looks big enough in January can leave you buying most of your power in July.
Forgetting the EV or the gas swap. Replacing a gas hot water system with a heat pump, or buying an EV, can add 3–10 kWh a day. Size for the household you’ll have in three years.
Oversizing past 133%. Panels beyond 1.33 times the inverter’s capacity don’t earn the rebate and mostly get clipped at midday.
Ignoring shade and roof direction. A chimney or neighbour’s tree across part of the array can cost more output than a few extra panels add. We model shading before recommending a size.
Sizing Solar for a Business
Commercial sizing works the same way, with better data. Instead of a quarterly bill, we use your meter’s 30-minute interval data to see your baseload, your weekday daytime demand and what happens on weekends. Offices, retail, cold storage and manufacturing with steady daytime loads usually justify the largest systems, because almost everything the panels produce gets used on site.
From 1 October 2026 the federal solar rebate is expected to cover commercial systems up to 1MW, up from 100kW, subject to final legislation. That makes getting the size right on a large roof worth tens of thousands of dollars. See our commercial solar service.
Frequently Asked Questions
What size solar system do I need for my house in Adelaide?
Divide your average daily electricity use (kWh) by 4.2, which is what 1kW of well-placed panels produces on an average Adelaide day. Multiply by about 1.1 if you have no battery, or 1.5 if you have or plan a battery. Most Adelaide homes end up between 6.6kW and 13.2kW.
How many solar panels do I need?
Divide the system size by the panel wattage. With 440W panels, a 6.6kW system is 15 panels, a 10kW system is about 23 panels and a 13.2kW system is 30 panels. Each panel needs roughly 2 square metres of roof.
Is a 6.6kW solar system enough for my home?
A 6.6kW system averages about 28 kWh a day in Adelaide, so it suits households using up to around 25 kWh a day without a battery. If you use more than that, run the pool or ducted air conditioning during the day, or plan to add a battery or EV, you will usually want something bigger.
What is the biggest solar system I can install on single-phase power in South Australia?
SA Power Networks allows up to 10kW of inverter capacity on a single-phase home. Because panels can be up to 133% of inverter capacity and still earn the rebate, that works out to about 13.3kW of panels. Three-phase homes can go up to 30kW of inverter capacity.
How much can I export to the grid in SA?
New SA systems choose between flexible exports, which allow up to 10kW per phase but can be reduced by SA Power Networks when the local network is busy, and a fixed limit of 1.5kW per phase. Most new installs go flexible. Either way, low feed-in tariffs mean exported power earns far less than power you use yourself.
Should I size my solar for a battery I might add later?
Yes. A battery needs spare daytime solar to charge, especially in winter, so plan for about 1.5 times your daily use. Choosing a hybrid inverter now also avoids replacing it later, and on single-phase power the battery inverter counts toward the same 10kW limit.
What size battery gets the best rebate?
Since 1 May 2026 the federal Cheaper Home Batteries rebate pays the full rate on the first 14 kWh of usable capacity, 60% of the rate from 14 to 28 kWh and 15% from 28 to 50 kWh. For most homes, a battery around 10 to 14 kWh gets the best value per kWh.
Does the Solar Sharer free power offer change what size solar I need?
Not much. From 1 July 2026 SA retailers must offer an opt-in plan with free power from 12pm to 3pm. Homes with a decent solar system already cover most of that window themselves. It matters more when choosing an electricity plan and deciding when to charge a battery or EV than when sizing panels.
