If you own a four bedroom house, working out what size solar system you actually need can feel like guesswork. The short answer for most Australian households is a 6.6kW to 10kW system, but the real answer depends on how you live. A family of five with ducted air conditioning, a pool pump, and plans for an electric vehicle has very different needs to a retired couple who spend most of their day at home.
This guide breaks down the numbers so you can match your solar system to your actual energy use, not just your bedroom count. For a broader overview across all home sizes, see our complete guide on what size solar system you need.
How Much Electricity Does a 4 Bedroom House Use
The average four bedroom home in Australia uses between 20 and 30 kWh of electricity per day. That works out to roughly 7,300 to 10,950 kWh per year. For context, Ausgrid’s 2023-24 data shows the overall NSW household average at around 17 kWh per day, but four bedroom homes with multiple occupants typically sit well above that.
A household running gas hot water and gas cooking will sit at the lower end. Switch those to electric and add a couple of split system air conditioners, and you are looking at 25 to 30 kWh daily.
Homes on the Mid North Coast tend to use more power in summer for cooling, though winters are mild enough that heating costs stay reasonable compared to Sydney or Melbourne.
- 2 occupants, gas hot water: 15 to 20 kWh/day
- 3 to 4 occupants, electric hot water: 22 to 28 kWh/day
- 5+ occupants, ducted AC, pool pump: 30 to 40 kWh/day
- All-electric home with EV: 35 to 50 kWh/day
Your electricity bill is the most reliable starting point. Look for the daily average usage figure, usually printed on the first page. If it says 25 kWh/day, that is your baseline.
What Size Solar System Covers a 4 Bedroom Home
For most four bedroom households, a 6.6kW system is the starting point and a 10kW system is the sweet spot for higher usage. Here is how the three most common residential sizes compare in New South Wales.
| System Size | Panels | Daily Output (NSW) | Annual Output | Best For |
|---|---|---|---|---|
| 6.6 kW | 15 to 16 | 25 to 26 kWh | 9,500 to 10,500 kWh | Average usage (20 to 25 kWh/day) |
| 8 kW | 18 to 20 | 30 to 32 kWh | 11,500 to 12,500 kWh | Moderate-high usage (25 to 30 kWh/day) |
| 10 kW | 22 to 24 | 38 to 40 kWh | 14,900 to 15,300 kWh | High usage, pools, EVs (30+ kWh/day) |
A 6.6kW system is the most popular size in Australia for good reason. It sits right at the 5kW single-phase inverter limit (which keeps costs down) while squeezing extra generation from those additional panels during morning and afternoon hours.
For a four bedroom home using around 22 kWh/day, it will comfortably cover your usage and still export surplus to the grid.
If your daily usage regularly exceeds 28 kWh, stepping up to an 8kW or 10kW system makes financial sense. The payback period on a larger system is often only six to twelve months longer, and you get significantly more generation headroom for years to come. At SolaXs, we install systems from 6.6kW right through to 13kW+ for larger properties across the Mid North Coast.
Factors That Change What Size Solar System You Need
Bedroom count is a rough proxy for home size, but these factors matter far more when sizing a solar system correctly.
Household occupants
More people means more showers, more cooking, more screens, and more laundry. A couple in a four bedroom home might use 18 kWh/day. A family of six in the same home could easily hit 35 kWh/day.
Hot water system
Electric hot water is one of the biggest energy draws in any home, often accounting for 30 to 40% of total usage. If you have an electric storage system, you need a larger solar array or a timer that heats water during peak solar hours.
Heat pump hot water systems are a more efficient alternative. Industry estimates put them at roughly 1,500 to 3,000 kWh per year compared to 3,500 to 4,500 kWh for a traditional electric storage unit. They pair well with solar and are increasingly popular across the Mid North Coast.
Air conditioning
Split systems add 2 to 5 kWh/day when running regularly. Ducted reverse cycle systems can draw 8 to 15 kWh/day during summer. On the Mid North Coast, expect heavier AC use from November through March.
If you have ducted air conditioning, see our guide on the best solar system for ducted air conditioning for specific sizing advice.
Pool pumps
A standard pool pump running six to eight hours daily adds 6 to 10 kWh. Variable speed pumps cut this significantly. If you have a pool, budget an extra 2 to 3 kW of solar capacity on top of your base needs.
Electric vehicles
Charging an EV at home typically adds 2,000 to 4,000 kWh per year to your electricity consumption, or roughly 8 to 15 kWh per day depending on how far you drive. This alone can push a household from a 6.6kW system into 10kW+ territory.
If you are planning to buy an EV in the next few years, size your solar system for that future usage now. You may also want to consider dedicated EV charger installation to get the most from solar-powered charging.
- Pool pump: add 2 to 3 kW to your system size
- Electric vehicle: add 3 to 5 kW to your system size
- Ducted AC: add 2 to 3 kW to your system size
- Electric hot water: add 1.5 to 2 kW to your system size
- Heat pump hot water: add 0.5 to 1 kW to your system size
Quick Sizing Guide by Household Type
Here is a practical breakdown based on real household scenarios we see regularly at SolaXs.
- Couple, gas hot water, no pool: 5kW to 6.6kW
- Family of 4, electric hot water, split AC: 6.6kW to 8kW
- Family of 5+, ducted AC, pool pump: 8kW to 10kW
- Large family, pool, EV, all-electric: 10kW to 13kW
These are starting points, not fixed rules. Your actual usage, roof orientation, and shading all play a role. North-facing roofs in NSW generate the most power, but east-west splits can work well too since they spread generation across more of the day.
Tip: Check your last four quarterly electricity bills and calculate the average daily kWh. Seasonal variation matters. A summer bill with heavy AC use tells a different story than a mild autumn quarter.
Should You Oversize Your Solar System
Yes. Almost always.
Solar panel prices have dropped significantly over the past decade, and the cost difference between a 6.6kW and an 8kW system is often only $1,500 to $2,500 at current market rates after the federal STC rebate. That extra capacity pays for itself within two to three years through additional feed-in credits and reduced grid imports.
For a deeper look at the numbers, see our guide on the economics of solar power for Australian homeowners.
There are three strong reasons to go bigger than your current usage suggests.
- Future-proofing. Energy use in Australian homes is trending upward as households switch from gas to electric appliances, add EVs, and install battery storage. A system that matches today’s usage might be undersized within three years.
- Battery readiness. If you plan to add a solar battery later, you need surplus generation to charge it. A perfectly matched system with no excess production gives a battery nothing to store.
- Better economics. Larger systems have a lower cost per watt. The marginal cost of each additional panel drops as the fixed installation costs (inverter, wiring, labour) are spread across more capacity.
The main constraint is how many panels your roof can accommodate. A 10kW system needs roughly 40 square metres of usable roof area.
If your roof is small, heavily shaded, or has multiple orientations, a CEC-accredited installer can design a layout that maximises output from available space.
Understanding Solar Rebates for Your System
The Australian Government’s Small-scale Renewable Energy Scheme (SRES) provides upfront rebates through Small-scale Technology Certificates (STCs). The rebate amount depends on your system size, location, and how many years remain in the scheme (which runs until 2030).
For a four bedroom home in NSW, typical rebate values in 2026 look like this.
- 6.6kW system: approximately $2,800 to $3,200 in STCs
- 8kW system: approximately $3,400 to $3,800 in STCs
- 10kW system: approximately $4,200 to $4,800 in STCs
These rebates are applied as a point-of-sale discount by your installer. The rebate reduces each year as the scheme winds down, so there is a genuine financial incentive to install sooner rather than later.
You can check current rebate values through the Australian Government’s energy rebates page. If upfront cost is a concern, there are also financing options for solar systems in Australia that spread payments while you benefit from savings from day one.
Important: To claim STCs, your system must be installed by a Clean Energy Council accredited installer. SolaXs holds full CEC accreditation and has been installing solar systems on the Mid North Coast for over 25 years.
Roof Orientation and Shading on the Mid North Coast
Where you live affects how much power your panels actually produce. On the Mid North Coast, we get strong solar irradiance year-round, with an average of 4.5 to 5.2 peak sun hours daily based on Bureau of Meteorology climate data. That is better than Sydney and significantly better than Melbourne or Hobart.
- North facing roof: Maximum output, ideal orientation in Australia
- East-west split: 10 to 15% less total output, but better morning and afternoon generation
- West facing: Good for households that use more power in the afternoon
- South facing: 25 to 30% less output, generally avoided unless no other option
Trees, neighbouring buildings, and roof features like chimneys or vents can create shading that reduces output. Modern panels with optimisers or micro-inverters handle partial shading much better than older string inverter setups.
Your installer should do a shading analysis before recommending a system size. You can learn more about how much power solar panels actually produce in different conditions.
How to Work Out the Right System Size for Your Home
Here is a straightforward process you can follow before talking to any installer.
- Find your daily usage. Check your last four electricity bills. Average the daily kWh figure across all four quarters to account for seasonal swings.
- Add future loads. If you are planning an EV, battery, heat pump hot water, or switching from gas, add the estimated daily kWh for those appliances.
- Divide by 4. In most of NSW, a 1kW solar system produces roughly 4 kWh per day on average. So if your adjusted daily usage is 32 kWh, you need an 8kW system as a minimum.
- Round up. Always go one size bigger than the calculation suggests. The price difference is small and the long-term benefit is real.
- Check your roof. Make sure you have enough unshaded roof space. Each panel needs about 1.7 to 2 square metres.
If you are on the Mid North Coast and want a professional assessment, our residential solar installation team can review your bills, inspect your roof, and recommend the right system size for your home. Contact SolaXs to book a free consultation.
With over 25 years of local experience and CEC accreditation, we design systems that actually match how you use power.
Frequently Asked Questions
Is a 6.6kW system enough for a 4 bedroom house?
For most four bedroom homes with average electricity usage of 20 to 25 kWh per day, a 6.6kW system will cover your needs and still export surplus to the grid. If you have ducted air conditioning, a pool pump, or an electric vehicle, you will likely need an 8kW or 10kW system instead.
How many solar panels do I need for a 4 bedroom home?
A typical 6.6kW system uses 15 to 16 panels (using standard 440W panels), while a 10kW system uses 22 to 24 panels. The exact number depends on the wattage of the panels your installer uses. Higher-wattage panels (440W to 470W) mean fewer panels for the same output.
Can I add more panels later if my usage increases?
Yes, you can expand your system later, but it is usually more cost-effective to oversize from the start. Adding panels later may require a second inverter or an inverter upgrade, which adds to the total cost. If you are planning an EV, battery, or hot water switch in the next few years, factor that into your initial sizing.
What is the difference between single-phase and three-phase solar?
Most Australian homes have single-phase power, which limits your inverter to 5kW AC output. This is why 6.6kW systems (5kW inverter with extra panel capacity) are so popular.
Three-phase homes can support larger inverters and higher export limits, making systems of 10kW and above more practical. Check your switchboard or ask your electricity retailer to confirm your phase type.
Should I get a solar battery with my system?
A battery lets you store excess solar generation and use it at night instead of buying from the grid. Whether it makes financial sense depends on your feed-in tariff, time-of-use rates, and how much of your usage falls outside daylight hours. Batteries are becoming more affordable, and government incentives like the federal solar battery rebate can reduce the upfront cost significantly.
How long does a solar system take to pay for itself?
Most residential solar systems in NSW pay for themselves within three to five years, depending on your usage, system size, and how much power you self-consume versus export. After the payback period, you are effectively generating free electricity for the remaining 20 to 25 years of your system’s lifespan. You can read more about whether home solar systems pay for themselves in Australia.
Do solar panels work on cloudy days?
Yes, solar panels still generate electricity on overcast days, though at reduced output (typically 10 to 30% of their full capacity). The Mid North Coast averages 4.5 to 5.2 peak sun hours daily year-round, which already accounts for cloudy periods.
This is one reason why oversizing your system is a smart strategy.
How much roof space does a solar system need?
Each solar panel needs roughly 1.7 to 2 square metres of roof space. A 6.6kW system needs around 28 to 32 square metres, while a 10kW system needs approximately 40 square metres. Your installer will assess usable roof area, accounting for shading, vents, and orientation.
Can I run a 4 bedroom house entirely on solar?
During daylight hours, a correctly sized solar system can cover all your electricity needs and export surplus to the grid. To run your home on solar around the clock, you would need a battery to store daytime generation for evening use.
A fully off-grid setup is possible but requires a larger system and significant battery capacity. Most households on the Mid North Coast stay grid-connected and use solar to offset the bulk of their bills.
What happens to excess solar power I do not use?
Any electricity your solar system generates that you do not use is exported to the grid. Your energy retailer pays you a feed-in tariff for each kWh exported, which appears as a credit on your electricity bill.
Feed-in tariff rates vary by retailer and change over time, so it is worth comparing offers. You can also learn more about how solar panels affect your power bill.