Want to save on energy bills and future-proof your home? Choosing the right solar panel system size is key. Here’s how you can get started:
- Understand your energy needs: Check your power bills to calculate your daily and monthly usage. For example, a typical Australian family uses 15–20 kWh daily.
- Consider your roof space: A 6.6 kW system needs about 25–34 m² of space, while a 3 kW system requires less.
- Plan for the future: Oversizing your system by 20% can cover future needs like EV charging or battery storage.
- Compare costs and savings: A 6.6 kW system costs about $7,400 and can save you up to $2,981 annually.
- Think about sunlight and shading: North-facing roofs are ideal, and tools like SunSPOT can help estimate your solar potential.
| System Size | Daily Output | Cost (after rebates) | Yearly Savings |
|---|---|---|---|
| 3 kW | 12 kWh | $5,400 | ~$1,500 |
| 5 kW | 20 kWh | $6,284 | ~$2,364 |
| 6.6 kW | 26–28 kWh | $7,400 | ~$2,981 |
Pro Tip: Use a 5 kW inverter with 6.6 kW of panels for the best value. Ready to start? Check your energy use, roof space, and budget to find the perfect system size.
1. Calculate Your Power Usage
Check Your Power Bills
The first step in selecting the right solar system is understanding your current electricity usage. Your power bill provides this information in kilowatt-hours (kWh), making it easy to calculate your daily energy needs.
To find your daily usage, take your monthly consumption from the bill and divide it by 30. For example, if your bill shows 600 kWh for the month, your daily usage is roughly 20 kWh. On average, Australian households use between 15 and 20 kWh per day.
| Household Type | Average Daily Usage | Monthly Usage |
|---|---|---|
| Single person | 8–12 kWh | 240–360 kWh |
| Average family | 15–20 kWh | 450–600 kWh |
| Large family with pool | 30–40 kWh | 900–1,200 kWh |
Measure Daytime Power Use
Solar panels work during daylight hours, so it’s crucial to understand how much energy you use when the sun is shining. For example, a 6.6 kW solar system in Brisbane can produce about 28 kWh on a sunny day, while the same system generates around 26 kWh in Sydney and 23 kWh in Hobart.
To get a clear picture of your daytime energy use:
- Check your smart meter data online.
- Request 12 months of interval data from your local electricity distributor.
- Review how your energy use changes with the seasons.
These insights will help you determine the right system size for your needs.
Plan for Future Usage
Think about how your energy needs might grow. Consider installing an inverter with 25% extra capacity to accommodate future additions like air conditioning, pool heating, electric vehicle charging, or home renovations.
Once you’ve calculated your energy needs, the next step is to assess your roof and location for solar installation.
2. Check Your Roof and Location
Measure Sun Exposure
The amount of sunlight your roof gets plays a big role in how much energy your solar panels can produce. In Brisbane, a well-placed solar system can generate up to 4.45 kWh of energy per kW installed daily throughout the year. This output varies by season, with the highest production typically occurring between September and March, where daily generation can reach 4.5–5 kWh.
Climate also influences performance. For instance, a 6.6 kW system will generate more energy in Brisbane’s warmer climate compared to cooler regions. To get a precise estimate of your roof’s solar potential, use tools like the SunSPOT solar calculator. It takes into account your location and roof features to provide accurate estimates.
Check Roof Direction and Angle
The direction and angle of your roof are critical for maximising solar panel efficiency. Research from the University of Queensland highlights:
“We have found Brisbane panels should be angled at 26 degrees, facing true north.” – Professor Tapan Kumar Saha, UQ Global Change Institute researcher
Here’s how roof orientation affects panel performance:
| Roof Direction | Performance Level |
|---|---|
| True North | 100% |
| North-East/North-West | 90% |
| East/West | 85% |
For Brisbane, the ideal setup is panels tilted at 28° from horizontal, facing due north. Most residential roofs, with pitches between 15° and 30°, are naturally suited for solar installations.
Look for Shade Issues
Shade can severely impact your solar system’s efficiency. Even a small shaded area on one panel can reduce the output of the entire system. To address shading:
- Identify current and future shading risks from trees, buildings, or chimneys.
- Observe how shade moves across your roof at different times of the day.
- Consider how seasonal changes in the sun’s position might affect shading.
If unavoidable shade exists, you can use technologies like microinverters or power optimisers. These allow each panel to work independently, reducing the impact of shading.
“If, for example, shade from a tree or a chimney is cast on even one of the panels in the string, the output of the entire string will be reduced to virtually zero for as long as the shadow sits there.” – Solar Choice
Most modern inverters now come with Maximum Power Point Tracking (MPPT) technology, which helps minimise energy loss due to partial shading.
Once you’ve assessed your roof’s sun exposure, direction, and shading, you’re ready to determine the ideal solar system size for your home.
How to estimate the size of your solar electric system
3. Pick Your System Size
Once you’ve assessed your energy needs and roof conditions, it’s time to decide on the right system size for your home.
Match Size to Power Needs
Your solar system should align with your household’s daily energy consumption. For example, a 6.6 kW system in Queensland typically generates around 26.4 kWh per day. Smaller households might only need a 3 kW system producing about 12 kWh daily, while larger households usually require systems between 5 kW and 6.6 kW.
“According to Ben McInerney, the larger your daily energy use, the larger your system must be.”
Choosing a slightly larger system can prepare you for future energy needs and may even eliminate power bills by taking advantage of feed-in tariffs.
The next step is to weigh the costs against the potential savings.
Compare Costs and Savings
Here’s a quick look at typical costs for quality systems:
- 3 kW system: $5,400
- 6.6 kW system: $7,400
A 6.6 kW system generates 120% more power than a 3 kW system but costs only 38% more. For a 5 kW system, the payback period is generally 3–4 years, thanks to reduced electricity bills and feed-in tariff earnings.
Check Panel-Inverter Match
After determining the costs, ensure your system components work well together. The Clean Energy Council allows the panel capacity to exceed the inverter capacity by up to 33%.
| Inverter Size | Maximum Panel Capacity | Typical Setup |
|---|---|---|
| 3 kW | 4 kW | 3.9 kW panels |
| 5 kW | 6.6 kW | 6.6 kW panels |
| 6 kW | 8 kW | 7.7 kW panels |
For most Australian homes, the standard setup is a 5 kW inverter paired with 6.6 kW of panels. Modern residential panels typically produce between 250W and 350W each, so a 6.6 kW system would require about 19–20 panels.
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4. Measure Roof Space
Once you’ve assessed your energy needs and roof orientation, the next step is to determine if your roof has enough space for a solar system.
Measure the Available Area
Measuring your roof accurately is key to placing solar panels effectively. Standard solar panels are generally about 1.7m x 1m, covering roughly 1.7 square metres each. Start by calculating your total roof area, then subtract areas needed for fire safety setbacks, existing fixtures, or irregular shapes that might reduce usable space.
Choose Space-Efficient Panels
If your roof space is tight, consider high-efficiency panels. These panels come in different sizes:
| Panel Type | Dimensions | Panel Area |
|---|---|---|
| Standard | 1.7m x 1.0m | 1.7 m² |
| Compact | 1.6m x 1.0m | 1.6 m² |
| Large Format | 2.0m x 1.5m | 3.0 m² |
High-efficiency panels produce more power per square metre but are typically more expensive. Use these measurements to figure out how much roof space you’ll need for your system size.
Space Requirements for a 6.6 kW System
For a 6.6 kW solar system, you’ll need around 15–20 panels, which translates to about 25.5–34 square metres of roof space. To maximise efficiency, aim to install panels facing north. If your layout requires an east-west orientation, plan for about 10% more space to offset the lower energy output.
If your roof has a complex layout or limited north-facing space, it’s a good idea to consult a professional installer. They can help optimise panel placement while ensuring all safety standards are met.
5. Review Costs and Rebates
Once you’ve matched your system size to your energy needs, it’s time to look at the financial side – costs, savings, and available incentives.
Check for Rebates
The Federal Government’s Small-scale Technology Certificates (STCs) can help cut down your upfront solar costs. Here’s how these rebates impact the pricing:
| System Size | Gross Price | STC Rebate | Net Price |
|---|---|---|---|
| 5kW | $7,920 | $1,636 | $6,284 |
| 6.6kW | $9,342 | $1,955 | $7,387 |
| 8kW | $11,740 | $2,633 | $9,107 |
“The advertised price for the system is the price after the installer has applied the rebate. They claim this rebate after they install the solar system.” – Luke Burnes, Local Cairns solar installer
Compare System Sizes and Costs
Generally, larger systems offer better value for money. For example, a 6.6kW system usually costs between $7,332 and $8,051 after rebates. Here’s what you can expect in terms of yearly and lifetime savings:
| System Size | Average Yearly Saving | Lifetime Saving |
|---|---|---|
| 5kW | $2,364 | $53,190 |
| 6kW | $2,981 | $67,072 |
| 7kW | $3,565 | $80,212 |
Considering these savings, it’s worth analysing how much you’ll save over the system’s lifetime.
Estimate Long-Term Returns
Solar systems typically pay for themselves in 3 to 6 years. To calculate your long-term returns, take these factors into account:
- Lower Power Bills: The right system size and feed-in tariffs can help reduce your power costs by up to 90%.
- Feed-in Tariffs: Rates between 10–14 cents per kWh can significantly add to your returns on excess energy.
- Future Energy Needs: Oversizing your system by about 20% can even eliminate your power bills entirely.
Keep in mind, the STC rebate program is set to end in 2030. Make sure to factor in both your current and future energy requirements when deciding on the system size.
6. Get Expert Help
Once you’ve assessed your energy needs and roof space, the next step is to finalise your system design with professional advice.
Use Solar Calculators
The Australian Government’s SunSPOT calculator provides detailed insights by analysing factors like your roof space, local climate, energy usage, feed-in tariff rates, installation costs, and potential savings.
“Working out the best system size can be complicated. Solar retailers and installers usually use specialist solar quoting software to determine a suitable system size and design, and estimate the projected savings.” – energy.gov.au
When using these tools, have your recent electricity bills handy. They help provide accurate estimates for:
| Calculation | What You’ll Learn |
|---|---|
| System Size | Recommended kW capacity based on your usage |
| Cost Estimate | Installation price after applicable rebates |
| Annual Savings | Expected reduction in your power bills |
| Payback Period | Timeframe for the system to pay for itself |
| Emissions Reduced | Impact on CO2 emissions, measured in tonnes |
These estimates are a great starting point before consulting a certified installer.
Find Certified Installers
Once you have an idea of your system size, verify your calculations with a certified installer. Look for professionals who are:
- Certified by Solar Accreditation Australia
- Compliant with the Clean Energy Council’s NETCC guidelines
- Listed on the Solar Accreditation Australia directory
These credentials ensure your installer follows strict standards and best practices for system design and installation.
Contact QVolt Solar
After gathering your estimates, QVolt Solar can help optimise your solar system design. We provide:
- Free Site Assessments: Our experts evaluate your roof space and sun exposure.
- Custom System Designs: Recommendations tailored to your energy needs.
- 30-Year Warranty: A workmanship guarantee you can trust.
- Performance Guarantee: Assurance that your system delivers as expected.
Schedule a consultation with QVolt Solar to finalise your solar system and start saving.
Next Steps
To determine the right solar system size for your home, follow these steps:
- Track your energy use: Record both your current and expected future power needs.
- Check your roof: Measure available space and note the orientation – north-facing roofs work best in Australia.
- Balance costs and savings: Compare the upfront investment with potential long-term savings.
- Use the SunSPOT calculator: Double-check your calculations for accuracy.
Once you’ve gathered your data, QVolt Solar can conduct a detailed site evaluation. This includes assessing your energy needs, roof space, sun exposure, and any future expansion plans.
| Assessment Area | Details We Review |
|---|---|
| Power Usage | Analysing daily patterns and seasonal changes |
| Roof Space | Measuring available space and identifying the best panel layout |
| Sun Exposure | Examining solar access and potential shading issues |
| Future Needs | Considering growth and expansion options |
After confirming the details, book a consultation with our certified installers. They’ll help finalise your system size and provide a customised installation plan. Plus, you’ll benefit from our 30-year workmanship warranty and performance guarantee.