What size system?

Current power usage

The first thing to look at when deciding what size solar system you will need is your current power usage, this can be found on your most recent electricity bill. Your bill should include your average daily units used over the billing period, this is measured in kilowatt-hours (kWh).

If you can, it’s a good idea to look at 12 months worth of bills to see how your usage changes throughout the year. For reference purposes, the average Perth household consumes around 18kWh of electricity per day.

The rule of thumb for Perth is that every 1kW of solar panels installed will generate an average 4.4kWh of energy per day. So if your daily consumption is 18kWh then you will need a 4.1kw solar system to match to your consumptions needs.

Battery ready

Consider whether battery storage is a worthwhile option for you. Batteries can be connected to your solar system to store the excess energy you generate during the day so that you can use it at night when your solar panels are no longer generating electricity. This saves you from having to buy that electricity back from the grid.

Batteries are new to the market and are currently expensive to purchase, as such they may not be worthwhile for most people initially. This doesn’t mean that you shouldn’t investigate getting a battery ready inverter included in your solar installation so you can have the option to get a battery added to your system at some point in the future.

Size of roof and area available

Another important consideration when sizing up your solar system in Perth is the amount of space available on your roof, especially on the prime north facing section. If you have other things already taking up space on your roof i.e. Solar hot water system, aircon etc then you will have to work around these when deciding where to place your solar panels. If space is limited on the north facing section of your roof, which it often is, then you will need to look at either the east or west facing sections to fit in the remaining panels.

Bear in mind that panels placed with a directly East or West facing orientation will not produce more than 85% of their rated output so you will need to add more panels to your solar system in order to generate your desired output.

Long term energy needs

Your long term energy needs may change in the future as such it is important to consider this when choosing your solar system.

Is your family growing? Changing household circumstances? Are your kids entering their teenage years and will start consuming more energy?


How much money you are willing to spend will also ultimately guide your decision about what size solar system to get. Remember though, that a purchase of a solar system should be regarded as an investment and the upfront cost of the system will effectively be paid back to you multiple times over the life of the system through reduced retail energy costs.

We also have finance options that we can offer with no money payable up front.

Sophisticated solar software

After taking into account the above factors, our sales representatives use sophisticated solar software to design the most efficient solar panel arrangement and placement on your roof as possible. The software can also be used to check for things such as shadowing effects at different times of the year from nearby trees or development that can impact the efficiency of you solar system.

Once we have designed the system we will generate a report to share with you whilst also going over the quote. The report will cover items such as estimated energy generation of the solar system per year, estimated greenhouse gas reduction per year, estimated dollar saving in electricity costs per year as well as the estimated energy output for each month of the year.

Give us a call today to chat about what size solar system is right for you.


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