Correctly Sizing a Solar System for Your Home or Business

Choosing the right size solar system is crucial to maximising the benefits of your investment. Whether you're considering solar for your home or business, proper sizing ensures you generate enough power to meet your needs while maximising return on investment. Here’s a guide to help you understand how to correctly size a solar system.

1. Assess Your Energy Usage

The first step in sizing a solar system is to understand your current energy usage. Review your electricity bills over the past 12 months to get a clear picture of your average monthly or quarterly energy consumption, measured in kiloWatt-hours (kWh). This data will provide a baseline for determining the size of the solar system you'll need.

Tip: Look for seasonal variations in your energy usage. Higher consumption during summer or winter may require a slightly larger system to ensure consistent coverage throughout the year. Note that solar generation is significantly lower in winter, especially in Victoria where output can drop to a third of that produced in summer depending on which direction your panels face.

2. Understand Peak Sunlight Hours

Solar panels generate electricity based on the amount of sunlight they receive, typically measured in Peak Sunlight Hours. This figure is calculated for a particular location by condensing the sunlight readings from sunrise to sunset into single figure. In Australia, based on figures provided by the Clean Energy Council, the average daily Peak Sunlight Hours across a full year range from 3.5 (Hobart) to 5 (Alice Springs). Melbourne comes in at 3.6 and Sydney is 3.9.

Example: If you live in Melbourne and your average daily power consumption is 24 kWh which is typical for a 4 person home, you’ll need at least a 6.6kW solar system (24 kWh divided by 3.6 Peak Sun Hours = 6.6 kW). Of course, if you want to cover your winter usage, the system will need to be much larger. The performance estimate graph on the previous page shows the daily averages by month for a 6.6kW system in Melbourne, and you can easily see the diminished production in winter.

3. Determine System Efficiency and Panel Ratings

Not all solar panels are created equal. The efficiency of the panels and the quality of the inverter will impact the overall output of your system. High-efficiency panels may cost more upfront but require less space and generate more electricity per square metre.

Consideration: If roof space is limited, opt for higher efficiency panels to maximise the energy production from the available area. Also, SolarEdge or Enphase inverter technologies will maximise the system output over traditional string inverters.

4. Factor in Future Energy Needs

When sizing your solar system, consider any future changes that could increase your energy consumption. This could include:

• Adding new appliances or electronics, and especially a swimming pool/spa or ducted air conditioning

• Installing an electric vehicle charger

• New additions to the family or children growing into power-burning teenagers

• Setting up a home business or transitioning to WFH

By assessing potential increases in energy usage, you can ensure your solar system will continue to meet your needs without requiring costly upgrades later on.

5. Account for System Losses

No solar system operates at 100% efficiency. Factors such as shading, dirt on panels, and inverter efficiency can reduce the system's overall output. It's essential to account for these losses when sizing your system.

Rule of Thumb: Assume system losses of around 10%. For example, if you calculate that you need a 6 kW system to meet your energy needs, you might consider installing 6.6 kW of panels to compensate for potential losses.

6. Consult with a Professional

While online calculators and guides such as this can provide a rough estimate, it's always best to consult with one of our energy experts to ensure you get the correct system size for your specific circumstances. We will conduct a detailed site assessment, considering factors like roof orientation, shading, and local climate to recommend the ideal system size. You’ll also get a range of system sizes to meet current and potential future needs, and winter coverage if that’s important to you.

Conclusion

Sizing a solar system correctly is key to achieving energy independence, reducing electricity bills, and contributing to a sustainable future. By considering your current and future energy needs, understanding local sunlight conditions, and factoring in system efficiency, you can make an informed decision about the right size solar system for your home or business.

At CBR Renewable Energy Solutions, we are committed to helping you make the most of your solar investment. Contact us today for a personalised consultation to find the perfect solar solution for your needs.