Choosing the right size for your solar system is crucial for maximising both energy production and financial returns. But how do you determine what size is the best fit for you? This guide walks you through key steps to make an informed decision.
When it comes to solar energy, “system size” is a term that relates to the overall electrical output capability of your solar setup, usually denoted in kilowatts (kW). Essentially, this number tells you how much electricity your solar system can produce when it’s operating at peak performance.
In Australia, common system sizes typically range from smaller configurations like 5 kW to mid-range options like 8 kW, and go up to larger setups of 10 kW or more.
To put these common system sizes in perspective, consider a common scenario: an 8 kW solar system. This means that, under ideal conditions, it has the potential to generate 8 kilowatts of electrical power per hour (kWh), which is the standard unit of energy you’ll find on your electricity bills and frequently used in energy discussions. That 8kWh could power a combination of the following appliances:
|Appliance||Energy Usage (kWh per hour)|
|Refrigerator||0.1 – 0.8|
|Air Conditioner (Window Unit)||1 – 2|
|Washing Machine||0.2 – 2|
|Clothes Dryer||2 – 6|
|Dishwasher||1 – 2|
|Oven||2 – 5|
|Microwave||0.6 – 1.5|
|Television||0.05 – 0.4|
|Computer||0.05 – 0.2|
|Vacuum Cleaner||0.5 – 1.5|
|Water Heater (Electric)||3 – 5|
Solar is an investment for your home – you invest money now, up-front to buy the system (or arrange finance), and it returns savings (lower energy bills) over the life of the solar system which is the return on your investment. If done well this can result in a great return for your up-front money – higher than having the money sit in a bank account for example. However, if you miscalculate, you could end up with underwhelming returns.
A common mistake is incorrectly sizing your solar system. Both under-sizing and over-sizing come with their drawbacks, affecting your return on investment (ROI).
For example if you:
Choosing an appropriately sized system which takes into account your current and future energy usage, export limits and feed-in tariffs is integral for achieving optimal system efficiency and long-term reliability.
Working out what size system you need involves several steps:
Step 1: Work out How Much Energy You Will Need Now and in the Future
The first step in determining the ideal solar system size is to understand your annual energy consumption. To do this, gather at least a year’s worth of electricity bills to calculate your average daily usage. This annual approach accounts for seasonality, providing a more complete picture of your energy needs.
If you’re considering adding a solar battery to your setup, don’t forget to factor in its charging needs. Batteries offer the advantage of storing excess solar energy generated during the day, enabling you to use it during peak periods or power outages. The energy needed to charge the battery should be incorporated into your overall energy calculations.
Finally, it’s crucial to consider your future energy needs. Are you planning to purchase energy-consuming appliances like air conditioning units or electric vehicles? These additions will increase your future energy usage and should be taken into account when determining your ideal system size.
By assessing both your current and future energy needs on an annual basis, you’ll be well-equipped to make an informed decision about the size of the solar system that will best meet your requirements.
Step 2: Consider Electrical and Network Limitations
After you’ve determined your energy needs, the next action is to understand the electrical and network limitations that might apply. A vital aspect to examine is whether your home is supplied with single-phase or three-phase electricity.
Being aware of your electricity network’s export limitations is also crucial. These rules specify the amount of surplus energy you can return to the grid, and exceeding these limits can result in financial or technical complications. For a single phase installation, export limitations are generally capped at 5 kWh. For a three-phase installation the export limitation is typically 15 kWh (5 kWh x 3 phases). This means that if your system is too big, any excess energy produced over and above what you consume and the export limit – is lost, making it essential to get your system size correct.
Step 3: Choose Your Equipment and Make Sure Any Limitations Are Taken into Account
Selecting the right equipment is crucial in determining your solar system size. Your choices regarding solar panels, inverters, and possibly batteries will significantly influence both the system’s performance and cost.
For solar panels, you have options for higher-wattage models that yield more electricity but come at a higher price. Alternatively, lower-wattage panels may be more budget-friendly but require more roof space. It’s a trade-off between upfront costs and power output.
When it comes to inverters, it’s an industry standard to oversize your solar panel capacity by 1.3 times the inverter’s capacity. The main reason for this is to ensure the inverter operates at maximum output consistently, thus optimising the overall system efficiency. For example, if you opt for a 10 kW inverter, you should aim for 13 kW of solar panels to maximise system performance.
When pairing panels and inverters you’ll also need to be aware of and take into account any limitations, such as panel and inverter compatibility. For instance, a 500W panel may be limited if paired with a 350W micro inverter.
If you’re considering adding a battery to your system, this will also influence the size of the solar setup you’ll need. Batteries are measured in kWh, much like your panels, and the size you choose should align with both your daily energy usage and the amount of solar production you aim to store. A battery allows you to utilise more of the solar energy you generate, thereby potentially reducing the size of the solar system needed.
By taking into account all these factors—panels, inverters, and batteries—you’ll be better equipped to decide on a solar system size that not only meets your energy needs but also adheres to any technical and financial constraints you may have.
Step 4: Can the Equipment Fit?
Theoretical calculations can provide a strong foundation, but it’s essential to consider the physical limitations of your property. Knowing your ideal system size is one thing; fitting it onto your roof is another.
Your roof’s dimensions, its structural integrity, and the available space for an inverter all play significant roles in the planning process. Panel orientation is another critical factor, as it directly impacts energy production. Even if the numbers make sense on paper, practical constraints could dictate adjustments.
It’s important to remember that the goal is not just to install a solar system but to install one that operates optimally in your specific setting. Issues like shading, roof angle, and even local regulations might necessitate smaller or differently arranged setups.
While a basic understanding of your energy needs is a good starting point, real-world calculations should be more detailed.
Here’s how to approach it step-by-step:
By following this comprehensive example, you’d need an 8 kW system consisting of roughly 18 panels at 440W each and a 6.15 kW inverter. This meets your daily energy requirements while also allowing for grid export, optimising your solar investment.
Sound easy so far? While the example calculation above gives you a basic understanding, it doesn’t cover all the factors that professionals take into account. This is where CEC-accredited solar system designers like Arkana Energy come into play.
We dive into the details, considering variables like your roof size, its orientation and tilt, as well as seasonal fluctuations in both energy usage and production. Shading issues and production losses due to heat are also considered. With advanced computer systems and a wealth of experience from over 10,000 installations, we can virtually model how sunlight will interact with your roof throughout the entire year.
Working closely with you, the homeowner, we develop a tailored plan that goes beyond general estimates. Although it’s helpful to have a rough idea of what system size you’ll need, entrusting this critical step to experienced professionals ensures you get a solar system that truly maximises your investment and meets all your energy needs.
After assessing your current and future energy needs, understanding your electrical and network limitations, and meticulously choosing your equipment, you’re now well-equipped to decide on the size of your solar system. It’s a decision that requires balancing various factors, including your home’s energy consumption, the physical space available for installation, equipment specifications, and budget.
This process might seem complicated, but remember, you’re making a long-term investment that will not only reduce your energy bills but also contribute to a more sustainable future. Consulting with experts, like our team at Arkana Energy, can provide invaluable insights tailored to your specific circumstances, helping you make the most informed choice possible.