How Many Solar Panels Do I Need? A Complete Homeowner Guide

One of the most common questions homeowners ask when considering solar is: “How many panels do I actually need?” It’s a smart question because the answer depends on your energy usage, roof size, panel wattage, future plans (like EVs or battery storage), and more. Get it right and you’ll maximise your savings and system performance. Get it wrong, and you may under-perform or overspend.

This guide walks you through the key factors, practical steps, and real numbers to help you estimate the right number of solar panels for your home, and what to talk about with your installer.

1. Start With Your Energy Usage

Before counting panels, you need to understand how much electricity your household uses. The easiest way is to look at recent bills and find your kilowatt-hours (kWh) used per day or month.

Many Australian homes use in the range of 15-25 kWh/day.
According to the CSIRO’s dataset, typical households show a broad spread, with variations based on family size, appliances, and climate.

Once you know your daily usage, you’ll have a baseline for how many panels you need.

2. Understand How Much Solar Panels Can Generate

The next step is estimating how much electricity your solar system can generate. A good rule of thumb in Australia: each 1 kW of solar panels can produce roughly 4 kWh per day under good conditions.

For example:

A 5 kW system → ~20 kWh/day
A 6 kW system → ~24 kWh/d

Of course, actual output depends on roof orientation, tilt, shading, and your location (NSW, VIC, QLD etc.).

3. Translate System Size Into Number of Panels

Once you’ve estimated your kW requirement, you can translate it into panel count. For instance:

If you use 20 kWh/day and you estimate you need, say, 5 kW of panel capacity → you might install a 5 kW system.
If each panel is rated at 400 W (0.4 kW), then 5 kW ÷ 0.4 kW = ~12 to 13 panels.
If you choose higher-wattage panels (like 450W), you might need fewer.

Sources show that many Australian homes install in the 5-7 kW system range for optimum ROI under current costs and roof space.

4. Consider Roof Space, Orientation & Shading

Even if you’ve done the math, your roof might limit what you can install:

Panel wattage: Higher-watt panels mean fewer panels and less roof area.
Roof orientation: North-facing in the southern hemisphere gives best output; east or west face still works but output may drop.
Tilt and angle: Ideal tilt often equals your latitude, but many sub-optimal angles still deliver good results.
Shading: Trees, neighbouring buildings or chimneys can reduce output, one shaded panel in a string inverter system can cut the whole string’s output. (Source)

5. Future Proofing: Batteries, EV's & Export Limits

When sizing your system, think ahead:

Battery storage: If you plan to add a battery, you may generate more during the day than you use, so a slightly larger system can make sense.
EV charging: If you’re planning an electric vehicle, your usage may significantly increase; consider that when sizing.
Export limitations: Some networks limit how much you can export to the grid; better to use your energy than rely on low feed-in tariffs.

6. Example Scenario

Here are three simplified example homes in NSW:

Small household (2–3 people)
• Daily Usage: ~15 kWh
• Suggested System: ~4 kW
• Approximate Panels (400 W): ~10 panels

Average family (4–5 people)
• Daily Usage: ~20 kWh
• Suggested System: ~5–6 kW
• Approximate Panels (400 W): ~13–15 panels

EV + large usage home
• Daily Usage: ~30 kWh+
• Suggested System: ~8–10 kW
• Approximate Panels (400 W): ~20–25 panels

These are rough guides; your installer will check roof size, panel efficiency, orientation and site specifics.

7. Getting a Quote: What to Ask Your Installer

When you sit down with your installer (like us at SunPeople), ask:

What daily kWh usage they assumed for sizing?
What panel wattage, brand and efficiency are they proposing?
What system size (kW) and how many panels?
What roof area will it take and how is shading managed
What does the modelling show for annual output and pay-back period?
Are there export limits in my network area?
If I add a battery later, will the system support it?

8. Pay-back and Value Remains Strong

In Australia today, solar system costs have fallen and output has improved. Many homes recoup their cost in under 5 years, depending on usage and incentives.

As electricity prices rise and rebates continue, your system can deliver decades of savings, making the number of panels you install both a technical and financial start point.

Conclusion

Sizing your solar panel system isn’t about picking an arbitrary number, it’s a smart calculation based on your usage, roof, future plans and budgeting. Start with your kWh usage, translate that into system size and panel count, check roof specifics and future-proof for batteries or EVs.

Need help figuring out your ideal system size? Reach out to us at SunPeople and we’ll walk you through it step by step.

Ready to maximise your savings and take control of your power?

Let’s power your home for a better tomorrow.

Sources:

Choice - How to size your solar panel system and maximise your electricity savings: https://www.choice.com.au/home-improvement/energy-saving/solar/articles/how-much-solar-do-i-need
Down to the Wire - How Much Solar Power Do I Need: A Complete Guide for Australian Homes: https://www.downtothewire.net.au/how-much-solar-power-do-i-need/
AHD - Typical House Energy Use: https://ahd.csiro.au/other-data/typical-house-energy-use/
SolarChoice - What Size Solar System Do I Need? A Comprehensive Guide: https://www.solarchoice.net.au/learn/design-guide/what-size-solar-system-do-i-need/
How many solar panels do I need to run my house Australia?: https://support.solarquotes.com.au/hc/en-us/articles/10869383329039-How-many-solar-panels-do-I-need-to-run-my-house-Australia