What Size Solar System Do You Actually Need?


With the adverse effects of global warming, people are becoming more interested in making environmentally friendly decisions, from using fewer plastic bags to reusable coffee cups, and of course, switching to renewable energy — which can be seen with the exponential growth in the number of households with a solar system installation. 

When you look up “solar system choices” into Google, you will receive over 159 million results, which can leave you overwhelmed. For starters, there are a lot of terminologies that seem straight from a physics test that you did not review for. You will also encounter a lot of computations and formulas that may seem gibberish, but with proper dissection and analysis, it can be simplified. 

For first-time buyers of solar systems, many questions come to mind. What system should you get? How many solar panels are needed? Where should it be installed? These questions, among a huge range of others, have likely crossed your mind. So, to make things easier, we have put together some information regarding one specific, and very important, question – what size solar system do I need?

Understanding Your Electricity Usage

The most important factor you need to know before determining the correct size of your solar PV system is how much electricity your home uses and how much you might be using in the future. Collect at least your last quarter’s electricity bills and study them to know how much power you’ve consumed over this period. From this, you will also know the daily average usage that your household uses. If you have a smart meter installed, it will be easier as you are able to see your daily usage by checking your account online. 

You may see the units kilowatt (kW) and kilowatt-hours (kWh) in your bill. It is important to know the difference between these units as they tell different measurements in your electricity usage. 

  • Kilowatt (kW) is a unit used to quantify the rate of energy transfer. The watts in solar panels tell us the maximum power a panel can deliver. 
  • Kilowatt-hours (kWh) is a measure of energy production or consumption over time. The kilowatt-hour (kWh) is the unit on your electricity bill because you’re billed for your electricity usage on a given period. A solar panel producing 300W for one hour will deliver or 0.3kWh of energy.

On a daily average, an Australian home uses around 15–20kWh, but this can go higher or lower depending on varying factors such as a family’s electricity consumption, the number of people residing in a given home, the area where they live, and more. For example, a one-person household will consume 8 kWh per day on average while a home with five people and a heated pool can consume around 40 kWh of electricity daily. 

Seasonal Usage and Frequency

When getting a solar system installed, it is necessary to know which time of the day when you will need to reap the benefits of solar power. Ask yourself the following: will there be no one using the electricity during the weekdays while you are at work and the kids are in school? Will you be mostly using electricity during the evening? If so, a solar system might not be that effective, unless you have a storage battery that will collect the solar energy during the day and store it until you use it at nighttime.

Aside from the time of the day, you also need to factor in the seasonal changes. Remember that most people will be using more electricity when the air conditioning is on during the scorching heat of the summer; meanwhile, the heaters will be running all throughout the cold winter days. 

This information will be pertinent for you to have a good understanding of how much power you usually use each day, how much you use on peak hours and the days or months that you are expecting a sudden surge of electricity usage.

Future usage

It’s better to be prepared than not at all, right? Of course, there will be sudden changes in your electricity consumption, hence, considering these changes is a great way to maximize your solar system. Some future needs to expect are:

  • working from home more often
  • planning to add a new baby
  • adding a swimming pool as pool pumps consume a lot of power!
  • switching from gas stove to electric stove 
  • getting an electric car 
  • improving the home’s resale value

In case that you already have a solar system installed, it can easily be upgraded and expanded to sustain your household needs. But keep in mind that this will have additional installation and expansion costs. 

So, What Solar System Size Do You Actually Need?

Now that you have an idea of how much electricity your household consumes and the peak hours of the day you use it, you now have the important information that will tell if your solar system’s capacity will be able to cover your power usage. 

We will assume that you’ll have a grid-connected system installed as this is the most common type in Australia and the more inexpensive option. A grid-connected system simply means your solar panels will be generating electricity during the day, while a grid connection will supply electricity when the solar panels are not generating sufficient power, such as during the night. 

One thing that is usually misunderstood when getting a solar system, is that the more solar systems there are, the more power you can get. However, the size or capacity of a solar system is the one you need to focus on as it is the maximum electricity output that your system can deliver. 

Your system might have 20 x 330W panels, or 24 x 275W panels – in either case, it is still a 6.6kW system, the number with real significance.

The Amount Electricity Per kW of Solar Panels

Solar systems are rated in watts or kilowatts. You will notice systems described as 4kW, 6.6kW, 12 kW, and so on. Each kW of solar panels is able to produce around 4kWh of electricity per day, hence, a 6.6kW solar system will generate about 26.4kWh on a good day.

This conversion is just a general rule of thumb as it can still vary depending on your location, the time of the year, the amount your solar panel is receiving, and the quality of your overall solar system. For example, in southern regions of Australia, it could be as low as 3.5kWh per day, while the same 1kW of solar panels in the northern regions could generate roughly 5kWh a day.

Is a bigger solar system size worth it?

The main reason why you’re getting a solar system installed is that you want them to cover as much of your power consumption. If your average power consumption on peak days is around 30 kWh, but most days of the week, just around 20kWh, it may not be worth adding additional solar panels just to cover those peak days. You could go with a 5kW solar system and just pay the consumed electricity from the grid on those occasional electricity-hungry peak days.

But as the prices of solar panels drop over time and there’s an economy of scale in installing a larger system, it is still an excellent idea to consider how big of a solar system to get with the assistance of your installer. The most common solar system installed in 2021 for residential usage is a 6.3kW solar system. It typically comes with 18 panels of 350W and a 5kw Inverter and overall, this is the most affordable solar system available in the market today. Meanwhile, if you are considering getting a storage battery connected with your solar system, bigger systems of 8 to 10 kWh are the most efficient.

Now, you may be thinking of going big with your solar system since any excess will be exported to the grid, which will result in feed-in tariffs, but the payment you will receive is generally very low, typically at around 4 to 8 cents per kWh. However, keep in mind that the payment you get can still vary depending on your energy retailer. 

The real benefit of getting a larger solar system is that it will be easier to add a storage battery so you can maximize the advantage of your inverter’s capacity, and simply generate more power throughout the day so that you are less likely to need grid power. And the excess power that you’re sending into the grid means there is more solar-sourced electricity in the grid for other households to use.

Still Don’t Know Which Solar System Size To Get?

With all the information above, calculating exactly how much capacity you need for your solar system can still be complicated. While this article may have given you the foundation of solar system sizes, at the end of the day, you still need to contact solar system installers to get a detailed quote that will accommodate your home and your needs. It is crucial to contact a solar installer with proven expertise and experience, such as Natural Technology Systems.

About Us

Natural Technology Systems are solar providers that have been in business for over 30 years, we are a business that South Australia trusts and provide expert, obligation free quotes and advice. We provide customers with the most cost-effective way to slash those power bills for your home or business.

Click here for a quick quote for your solar power needs or contact us today at (08) 7081 9830

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