How Many Solar Panels Does Your Perth Home Really Need? A Sizing Guide

When Perth homeowners start considering solar, one of the first questions that comes up is simple: how many panels do I really need? Some think 10 will be enough, while others imagine 20 or more. The truth is that the right number varies for every home, depending on energy use, roof space, and long-term plans.

Getting the size right is important because it directly affects how much the system will cost, how well it performs, and how quickly it pays for itself. Too few panels and you may still face high electricity bills, too many and you could be spending more upfront than necessary.

For a broader overview of how solar works and what to expect as a first-time buyer, check out our full guide: Getting Started with Solar: A Beginner’s Guide for Perth Homeowners.

This article, however, focuses more closely on panel count and system sizing so you can understand what’s practical for a Perth household.

Steps to Calculate the Right Number of Solar Panels

Getting the right solar panel count is not about guesswork. By following a simple process, you can match your household energy needs with the right system size, avoid overspending, and ensure your panels deliver maximum value for your Perth home.

Step 1: Find Your Home’s Electricity Usage

The first step in working out how many solar panels you need is to understand how much electricity your household actually uses. Your daily energy consumption, measured in kilowatt-hours (kWh), is the biggest factor in system sizing.

For example, smaller homes in Perth might use between 10 and 15 kWh per day, while larger families can easily reach 25 kWh or more. Seasonal changes also matter, as many households see a spike in summer when air conditioning is running more often.

The easiest way to check your usage is by looking at your Synergy electricity bill, which shows your average daily consumption. Let’s say a medium-sized family in Perth uses around 20 kWh per day.

Here’s how you turn that into a system size:

Step A: Divide your daily usage by Perth’s average of 5.5 sun hours.
Example: 20 kWh ÷ 5.5 = ~3.6 kW.
Step B: Add a buffer of around 20% to allow for system losses like inverter efficiency and panel performance drops.
3.6 kW × 1.2 = ~4.3 kW.
Step C: Convert that figure into the number of panels based on panel wattage.

With 370W panels: 4.3 kW ÷ 370W ≈ 12 panels.

With 450W panels: 4.3 kW ÷ 450W ≈ 10 panels.

So, a Perth home using 20 kWh per day would generally need a 4–5 kW system, which translates to roughly 10–14 solar panels depending on the type of panels chosen.

Step 2: Consider Your Roof Space and Location

Your roof is one of the most important factors in deciding how many panels you can install. A large, north-facing roof with minimal shading will allow for more panels and better efficiency, while smaller or shaded areas may limit your options.

Start by looking at the available surface area. Each solar panel is usually about 1.7m by 1m, so a system of 12 to 14 panels can take up around 20 to 24 square metres. If your roof has multiple pitches or limited clear space, installers may need to split the system across different sections, which can affect performance.

Shading is another key point. Even small amounts of shading from nearby trees, chimneys, or taller buildings can reduce output, though modern inverters with panel-level optimisation help to minimise these losses.

Orientation also plays a role. In Perth, panels facing north deliver the best overall performance, while east- or west-facing arrays spread production across the morning or afternoon. A slight tilt in roof pitch is not a problem, as Perth’s strong sun ensures panels still capture plenty of energy.

Panel efficiency matters as well. Standard 370W panels will require more roof space than 450W panels to achieve the same system size. For instance, a 5 kW system might need 13–14 standard panels but only 11–12 high-efficiency panels.

Finally, think about your energy use versus export. While Perth enjoys some of the highest solar irradiance in Australia, WA’s feed-in tariff for exported power is relatively low. This means most households save more money by sizing their system to cover daytime usage rather than oversizing and exporting excess energy back to the grid.

Step 3: Account for Future Needs

While your current energy use is the starting point, it’s equally important to think ahead. Many Perth households are making changes that will increase their electricity demand in the coming years. Planning for these future needs ensures you won’t end up with a system that feels too small too soon.

Some common additions that can boost your usage include:

Electric vehicle charging: EV ownership is growing rapidly in WA, and charging at home can add 5–15 kWh per day to your usage.
Pool pumps or heating: A backyard pool is a major energy draw, especially in summer when filtration and heating systems run longer.
Home extensions or growing families: Adding new rooms, appliances, or simply having more people at home will naturally push your electricity demand higher.

Installing a slightly larger system upfront can be a smart move. While the upfront price is higher, it helps avoid the hassle and expense of system upgrades later. A bigger system also tends to shorten payback time, since it maximises bill savings over the long run.

If much of your household consumption happens in the evening, pairing your solar array with a battery is worth considering. A battery allows you to store excess power generated during the day and use it at night, reducing your reliance on the grid.

In this case, sizing your system a little larger makes sense, as you’ll need enough generation capacity to both meet daily usage and charge the battery effectively. Thinking beyond your immediate needs ensures your system remains a good fit not just for today, but for the lifestyle changes you anticipate in the future.

If you’d like to explore the basics of installation, system components, and how to get started as a new solar user in Perth, our beginner’s guide to solar in Perth covers everything in detail.

The Verdict: What Size System Is Right for You?

For most Perth households, the right solar system sits in the 12 to 24 panel range, depending on your energy use, roof size, and panel efficiency.

Small homes / low usage (1–2 people): typically 10–12 panels (around 3–4 kW).
Medium homes / families: around 15–20 panels (about 5–6.6 kW).
Large homes / high usage: 20–30+ panels (8–10 kW or more).

As an example, a 6.6 kW solar system could mean about 18 panels at 370W each, or closer to 15 panels with higher-efficiency 440W models. Roof layout, shading, and budget will also influence the final count.

The key is to size your system around your own consumption patterns and future plans, not just the maximum your roof can handle. With Perth’s strong sunlight and rising electricity costs, a well-matched solar system can provide reliable savings for years to come, making the investment worthwhile.

Get Expert Advice on Your Perfect System

At Fritts Solar, we guide Perth households in choosing and installing the right number of panels to suit their lifestyle and budget. Whether you need a smaller setup to cut bills or a larger system that supports future energy needs, our team designs solutions that deliver long-term value.

Curious about the exact number of panels your home requires? Contact us today for a tailored solar assessment and get a system sized perfectly for you.

Tags: solar panels