How many solar panels do I need? For most Adelaide homes, the answer is between 15 and 24. A typical three or four person household uses around 18 to 22 kWh a day, which points to a 6.6kW system — that is 15 to 17 panels at today’s 400 to 440W panel sizes. Larger homes with a pool, ducted air conditioning or an electric vehicle usually land at 10kW to 13kW, or 23 to 30 panels. This guide shows you how to answer “how many solar panels do I need” for your own home in three steps using nothing more than your last electricity bill, and explains the roof, orientation and export-limit factors that change the answer in South Australia.
The Quick Answer: Panel Counts for Adelaide Homes
If you just want a ballpark answer to “how many solar panels do I need”, this table maps household size to a recommended system and panel count. It assumes a north-facing, unshaded roof in Adelaide and modern 440W panels. Your actual usage matters far more than the number of people, so use this as a starting point, then follow the three-step method below.
| Household | Typical daily use | Recommended system | Panels (440W) | Roof space needed |
|---|---|---|---|---|
| 1 to 2 people, small unit or townhouse | 8 to 12 kWh | 3kW to 5kW | 7 to 12 | 14 to 24 m² |
| 2 to 3 people, standard home | 12 to 18 kWh | 5kW to 6.6kW | 12 to 15 | 24 to 30 m² |
| 3 to 4 people, family home | 18 to 25 kWh | 6.6kW | 15 to 17 | 30 to 34 m² |
| 4 to 5 people, ducted air con or pool | 25 to 35 kWh | 8kW to 10kW | 18 to 23 | 36 to 46 m² |
| Large home, EV, pool and battery | 35 kWh or more | 10kW to 13.2kW | 23 to 30 | 46 to 60 m² |
Notice that the 6.6kW system appears in the middle. There is a reason it is the most installed size in South Australia: it is the largest array most single-phase homes can pair with a 5kW inverter under the standard oversizing rules, which keeps the rebate value high and the export limit simple. Our 6.6kW solar system for Adelaide page covers that system in detail.
How Many Solar Panels Do I Need? Work It Out in 3 Steps
The question “how many solar panels do I need” really comes down to three numbers: how much electricity you use, how much each kilowatt of panels produces in Adelaide, and how many watts each panel delivers. Here is how to get each one.
Step 1: Find your daily electricity use
Your electricity bill shows total kilowatt-hours (kWh) used for the billing period, usually 90 days. If you cannot find it, the Australian Government’s Energy Made Easy site can pull your usage history directly from your smart meter data. Divide that figure by the number of days to get your daily average. If you have a bill from summer and one from winter, average the two, because Adelaide households often use more in summer for cooling and more in winter for heating, and a single bill can mislead you.
Example: a bill shows 1,800 kWh over 91 days. That is 1,800 ÷ 91 = 19.8 kWh per day.
Step 2: Convert daily use into system size
In Adelaide, a well-installed north-facing system produces roughly 4.2 kWh per day for every 1kW of panels, averaged across the whole year. This figure is consistent with the postcode-zone ratings published by the Clean Energy Regulator, which places Adelaide in Zone 3. Summer days are higher (5 to 6 kWh per kW) and winter days lower (2.5 to 3 kWh per kW), but 4.2 is a reliable annual figure for sizing.
Divide your daily use by 4.2 to get the system size in kW that would cover your total annual consumption.
Example: 19.8 kWh ÷ 4.2 = 4.7kW. Rounding up to the nearest common system size gives 5kW, or 6.6kW if you want headroom for a future battery or EV.
Step 3: Convert system size into panel count
Divide the system size in watts by the wattage of the panel being installed. In 2026, residential panels are typically 400W to 470W, with 440W being the most common mid-range choice.
Example: 6,600W ÷ 440W = 15 panels. The same 6.6kW system needs 17 panels at 400W, or 14 panels at 470W.
| System size | Panels at 400W | Panels at 440W | Panels at 470W | Adelaide daily output (annual avg) |
|---|---|---|---|---|
| 3kW | 8 | 7 | 7 | 12 to 13 kWh |
| 5kW | 13 | 12 | 11 | 20 to 22 kWh |
| 6.6kW | 17 | 15 | 14 | 26 to 28 kWh |
| 8kW | 20 | 18 | 17 | 32 to 34 kWh |
| 10kW | 25 | 23 | 21 | 40 to 42 kWh |
| 13.2kW | 33 | 30 | 28 | 53 to 56 kWh |
Higher-wattage panels mean fewer panels for the same output, which matters on a small or complicated roof, and it is why the answer to “how many solar panels do I need” has been falling every year as panel wattages rise. They do not mean more electricity. A 6.6kW array is a 6.6kW array whether it is 14 panels or 17. Our comparison of the best solar panels in Australia for 2026 explains which brands sit at each wattage.
How Much Roof Space Do Solar Panels Need?
A modern residential panel measures roughly 1.1 metres by 1.7 to 2.3 metres, so allow about 2 square metres per panel once you include the small gaps between rows and the setback from roof edges required for safety and wind loading.
- 6.6kW (15 panels): around 30 m², or a roof section roughly 6m by 5m
- 10kW (23 panels): around 46 m², usually spread across two roof faces
- 13.2kW (30 panels): around 60 m², typically needs three faces or a large single north-facing plane
Most Adelaide homes have far more roof than this, so roof area is rarely what limits how many solar panels you can install. The real constraint is usually not total area but how much of it faces the right way and is free of shade, vents, skylights and air conditioning units. That is something we measure precisely during a free site assessment rather than estimating from satellite imagery.
5 Things That Change the Answer in South Australia
The formula gives a clean number, but in practice “how many solar panels do I need” depends on five site-specific factors that no online calculator can see.
1. Roof orientation
North-facing panels in Adelaide produce the most energy across the year. East and west faces produce around 12 to 15 percent less each, but they spread generation across the morning and afternoon, which can actually suit a household that is out during the middle of the day. An east-west split is a very common and effective layout. South-facing panels produce roughly 25 to 30 percent less and are generally a last resort. If your only usable roof faces east or west, add two to three panels to compensate.
2. Shading
Even partial shade from a tree, chimney or neighbouring building can cut output from an entire string of panels, not just the shaded one. Where shade cannot be avoided, panel-level optimisers or microinverters limit the loss to the affected panels only. We assess shading across the whole day at your site, because a roof that is clear at noon can be shaded at 3pm in winter.
3. Inverter oversizing and the 133 percent rule
Under the Clean Energy Council design guidelines that govern the federal STC rebate, panel capacity can be up to 133 percent of the inverter’s rated output. That is why a 5kW inverter is so often paired with 6.6kW of panels — it is the maximum allowed. Oversizing makes sense because panels rarely produce their full rated output in real conditions, so a 6.6kW array on a 5kW inverter loses very little at the peak and gains considerably in the mornings, evenings and winter. If you want more than 6.6kW, you step up to an 8kW or 10kW inverter, which brings us to export limits.
4. SA Power Networks export limits
In South Australia, SA Power Networks typically limits a single-phase home to exporting 5kW to the grid. A three-phase home can usually export more. This does not stop you installing a larger system — a 10kW array on single phase simply has its export capped at 5kW while you use the rest yourself. With feed-in tariffs now only 2 to 8c per kWh, the value of exports is low anyway, so a larger array is best justified by higher self-consumption or a battery rather than by exports. Our South Australia feed-in tariff guide explains why.
5. What you plan to add later
Sizing purely to today’s bill is the most common mistake we see. A home battery, an electric vehicle, a pool pump, a heat pump hot water system or a switch from gas to induction cooking can each add 5 to 15 kWh a day. If any of those are likely within the next five years, size for them now. Adding panels later is possible but usually costs more per panel than including them in the original install, and can complicate the rebate paperwork.
Three Worked Examples From Adelaide Homes
Three real household profiles show how differently “how many solar panels do I need” can play out across Adelaide, even with the same method.
A couple in a Prospect townhouse
Daily use of 11 kWh, both working from home two days a week, gas hot water, no plans for an EV. 11 ÷ 4.2 = 2.6kW, so a 3kW to 5kW system covers them comfortably. With a small north-facing roof section, we would recommend 5kW, or 12 panels at 440W, to allow for a modest battery later. Going to 6.6kW would mostly generate exports worth 5c.
A family of four in Golden Grove
Daily use of 21 kWh, ducted reverse-cycle air conditioning, electric hot water, one parent home during the day. 21 ÷ 4.2 = 5kW. Because daytime usage is high and a battery is on the wish list, we would recommend 6.6kW, or 15 panels at 440W on a 5kW hybrid inverter, wired battery-ready. This is the classic Adelaide family install and sits at the sweet spot for STC rebate value.
A large home in Mount Barker with a pool and an EV
Daily use of 38 kWh including EV charging and a pool pump, three-phase power, large tiled roof. 38 ÷ 4.2 = 9kW. With an EV that could be charged from surplus solar and a 28kWh battery to cover the evening, we would recommend 10kW to 13.2kW, or 23 to 30 panels. This is the profile that suits our 10kW solar and 28kWh battery package, and our guide to EV charging with solar in South Australia goes deeper on the numbers.
Is a Bigger System Always Better?
Not automatically, and this is where people asking “how many solar panels do I need” often go wrong. Ten years ago, when feed-in tariffs were 20c or more, every extra panel paid for itself through exports. In 2026, with exports worth 2 to 8c, a system far larger than your consumption produces a lot of low-value electricity. The best return comes from a system sized so that most of what you generate is either used directly or stored. That said, the cost per panel falls as systems get larger, and the STC rebate scales with system size, so going one step up from your calculated size — say 6.6kW instead of 5kW — is usually sensible if you expect your usage to grow. Our 2026 solar panel cost guide shows how price per kW changes across system sizes.
Common Mistakes When Sizing a Solar System
After hundreds of site assessments across Adelaide, these are the errors we see most often when homeowners try to answer “how many solar panels do I need” on their own.
- Using a single winter or summer bill. Average at least two seasons, or use a full year of data from your retailer’s app.
- Sizing for exports. At 5c per kWh, exports rarely justify extra panels. Size for self-use and storage.
- Ignoring the export limit. A 10kW system on single phase will be capped at 5kW export. Make sure the extra capacity is being used, not curtailed.
- Filling the roof because it is there. A quote that maximises panel count without asking about your usage is a red flag.
- Forgetting future loads. An EV or heat pump added next year can double your consumption. Plan for it now.
- Accepting a satellite-only assessment. Aerial imagery cannot see shading, roof condition or switchboard capacity. Insist on a site visit.
Frequently Asked Questions
How many solar panels are in a 6.6kW system?
A 6.6kW system uses 15 panels at 440W, 17 panels at 400W, or 14 panels at 470W. The panel count depends only on the wattage of the panels chosen; the total output is the same. In Adelaide, a north-facing 6.6kW system generates around 26 to 28 kWh per day averaged across the year.
How many solar panels do I need for a 3-bedroom house in Adelaide?
For a typical three-bedroom Adelaide home with three or four occupants, the answer to “how many solar panels do I need” is 15 to 17. These homes use 18 to 25 kWh a day and suit a 6.6kW system. If the home has ducted air conditioning, a pool or an electric vehicle, an 8kW to 10kW system of 18 to 23 panels is more appropriate. Your actual bill is a better guide than the number of bedrooms.
How many solar panels do I need for a 10kW system?
A 10kW system needs 23 panels at 440W, 25 panels at 400W, or 21 panels at 470W, and requires roughly 46 square metres of roof. It generates around 40 to 42 kWh a day in Adelaide and suits larger households, homes with EVs or pools, and anyone pairing solar with a 15kWh or larger battery.
How much roof space do I need for solar panels?
Allow about 2 square metres per panel including gaps and edge setbacks. A 6.6kW system of 15 panels needs around 30 square metres, a 10kW system around 46 square metres, and a 13.2kW system around 60 square metres. The usable area is what matters — roof sections facing north, east or west with no shading, vents or skylights in the way.
Can I add more solar panels later?
Yes, but it is usually more expensive per panel than including them in the original installation, and newer panels may not match the wattage or voltage of the existing string. Adding panels can also require a larger inverter and a new grid connection application with SA Power Networks. If there is a reasonable chance your usage will grow, sizing up at installation is almost always the cheaper path.
Does the number of panels affect the solar rebate?
The federal STC rebate is calculated on system capacity in kilowatts, not panel count, so a 6.6kW system attracts the same rebate whether it is 14 or 17 panels. The rebate scales with size, meaning a 10kW system receives roughly 50 percent more STC value than a 6.6kW system. Panel capacity cannot exceed 133 percent of the inverter rating to remain eligible.
How many solar panels do I need to charge a battery?
To fully charge a battery from solar and still power the house during the day, you need surplus generation at least equal to the battery’s capacity on an average day. In panel terms, that means 15 to 17 panels for a 10kWh battery, 18 to 23 panels for a 15kWh battery, and 23 to 30 panels for a 28kWh battery. A 10kWh battery pairs well with 6.6kW of panels. A 15kWh battery is best matched with 8kW to 10kW. A 28kWh battery needs 10kW to 13.2kW. Our 15kWh solar battery for Adelaide page shows the pairing in detail.
Get Your Exact Panel Count for Free
The three-step method above will answer “how many solar panels do I need” to within a panel or two. To get it exactly right, Peace Electrical and Solar offers a free site assessment anywhere in greater Adelaide. Our SAA-accredited, in-house licensed electricians measure your usable roof, check shading across the day, confirm your switchboard and phase configuration, and review your bills, then give you a fixed-price quote with all 2026 rebates applied. Based in Salisbury North, we service every Adelaide suburb from Gawler to Morphett Vale and out to the Adelaide Hills.
Generation figures assume a north-facing, unshaded roof in Adelaide and an annual average of approximately 4.2 kWh per kW of installed panels per day. Actual output varies with orientation, tilt, shading, panel model and weather. Panel counts assume 400W, 440W and 470W panels as indicated. Export limits are set by SA Power Networks and depend on your connection type.
