How to Choose the Right Solar System Size for Your Home: A Complete Guide
Choosing the correct solar system size for your home is essential to maximizing your return on investment (ROI) and ensuring that your energy needs are met efficiently. However, determining the ideal system can be tricky, especially when sales representatives may push for the largest system available. While a bigger system can produce more energy, it doesn’t always lead to the best financial returns.
This comprehensive guide will walk you through the key factors that determine the optimal solar system size for your home, helping you make an informed decision.
How to Determine the Right Solar System Size?
With the drop in feed-in tariffs over the last decade, the days of profiting from selling excess solar energy back to the grid are largely behind us. Feed-in tariffs, or the rates paid by electricity retailers for the solar power you send back to the grid, have fallen significantly. This change has led to an important guiding principle when it comes to sizing solar systems:
To maximize your ROI, it’s ideal to size your solar system so that its output matches your home’s daytime energy consumption.
When your system is properly sized to your daily energy needs, you minimize the amount of surplus energy sent back to the grid. Since the feed-in tariffs are quite low, relying on selling surplus energy is no longer a sound financial strategy. Instead, you want to consume as much of the solar energy you generate as possible.
How to Calculate Your Energy Needs?
The first step in choosing the ideal solar system size for your home is to assess how much electricity it uses. Most electricity bills will show your monthly or quarterly energy consumption in kilowatt-hours (kWh). The goal is to install a system that will generate enough solar power to cover your daytime electricity needs, as this is when your solar panels are producing energy.
Consider these factors:
>> Your total daily energy consumption: Look for this on your electricity bill. Keep in mind that this includes both day and night usage, so focus primarily on the energy you use during daylight hours.
>> Seasonal variations: Energy consumption can fluctuate depending on the season, with higher usage in summer due to air conditioning or in winter if you use electric heating.
>> Potential future increases: If you plan to purchase electric appliances, expand your home, or switch to electric heating, these changes will increase your energy consumption.
After gathering this information, you can use a solar payback calculator or consult with a solar provider to find the system size that will best meet your needs
What’s the Best Solar System Size for Your Home?
Solar systems are often categorized by their capacity in kilowatts (kW), which indicates the maximum power the system can generate under ideal conditions. The best solar system size for your home will depend on your usage patterns, particularly whether your electricity use is focused on peak times (morning and evening) or spread more evenly throughout the day.
Let’s explore two common usage profiles: homes that experience peak electricity demand in the morning and evening, and homes with higher daytime energy consumption.
Solar System Sizing for Morning and Evening Peaks
For households that use most of their electricity in the early morning and late evening (before and after work hours), a 6kW system typically offers the best return on investment. Here’s a breakdown of potential system sizes and their expected payback periods:
A 6kW system strikes a good balance between upfront costs, savings, and the time it takes to recoup your investment. For homes with peak demand in the mornings and evenings, this size ensures you generate enough solar power during the day to meet your basic energy needs and reduce your reliance on grid power in the evenings.
Solar System Sizing for Daytime-Focused Usage
For homes where more energy is used during the day—such as households with stay-at-home workers, retirees, or energy-intensive appliances running during daylight hours—a 6kW system is also typically the best option. Here’s how the numbers break down:
A 6kW system once again emerges as the best balance of cost and ROI for homes with higher daytime usage. By generating energy when it’s most needed, these homes can significantly reduce their reliance on the grid.
Key assumptions for both tables:
30 cents for every kWh of electricity, plus a 7 cent feed-in tariff.
Solar system prices are based on Sydney rates from the Solar Choice Price Index.
System generation is calculated based on panels installed at a 30-degree tilt, facing north.
Smaller systems (below 6kW) tend to offer lower ROI, as the cost per kilowatt installed is higher. In most cases, homeowners opt for at least a 6kW system unless they are constrained by roof space or budget.
Should You Oversize Your Solar System for Future Needs?
While installing the optimal size for your current needs is important, it’s also worth considering future changes to your household energy consumption. It’s possible to expand your solar system later, but doing so often comes with additional costs that could be avoided by installing a slightly larger system from the start.
Many homeowners choose to oversize their systems to account for potential future energy needs. Here are some common reasons why you might want to install a larger
System Upfront:
- Adding an air conditioning unit: Installing air conditioning can significantly increase your electricity consumption, especially in hotter months.
- Building a granny flat or second dwelling: If you plan to add a secondary living space, your electricity usage will increase accordingly.
- Installing a swimming pool: Pools require energy to run pumps and filters, which can add substantial daily power needs.
- Switching from gas to electric appliances: Converting your heating, cooking, or water heating from gas to electric will naturally increase your power usage.
- Working from home: If you or other household members start working from home, daytime energy consumption will rise.
- Purchasing an electric vehicle: Charging an electric car adds a significant new energy load to your household.
- Installing a solar battery: While batteries don’t consume energy themselves, they store excess solar energy, which can be beneficial if your system is slightly oversized.
If any of these factors are likely for your household, it might make sense to invest in a larger system now, rather than facing higher costs for an expansion later.
Potential Limitations to Sizing Your Solar System
In some cases, even if you want to install the optimal system size, you may face limitations that prevent it. These constraints can include:
Network restrictions: Depending on your local electricity network, there may be limits on the size of the solar system you’re allowed to install. This is often the case in areas where large systems could overload the grid.
Roof space and shading: The amount of available roof space is another important consideration. If your roof is small or partially shaded, you may not be able to fit as many panels as you’d like.
Budget constraints: Finally, the cost of installation can be a limiting factor. While a larger system may offer better long-term savings, not everyone has the budget for a bigger upfront investment.
Do You Need a Solar Battery?
While solar batteries offer the promise of energy independence, they are a considerable investment and don’t always provide a quick return on investment. For most homeowners, the cost of batteries currently outweighs the savings. However, there are several reasons why you might still consider installing a solar battery, even if the primary goal isn’t immediate savings.
Common Reasons for Installing a Battery
- Complete energy independence: If you want to go entirely off-grid, you’ll need enough battery capacity to power your home through cloudy days or periods of low solar production. This often means installing a system large enough to cover 2-3 days of energy needs, along with a backup generator.
- 70-80% energy independence: Many homeowners aim for partial energy independence by covering 70-80% of their electricity needs with solar and battery storage. This approach reduces the upfront cost while still allowing you to minimize reliance on the grid
- Peak period independence: If your electricity provider charges higher rates during peak periods, you can use a battery to store solar energy during the day and use it in the evening, avoiding peak prices.
Emergency backup: Even if you stay connected to the grid, a small battery can provide emergency backup power during outages. This is particularly useful for essential appliances, such as refrigerators or medical devices.
Conclusion
Choosing the right solar system size is crucial to maximizing your energy savings and achieving the best return on investment. By matching your system’s output to your home’s daytime energy needs and considering potential future growth in energy usage, you can ensure long-term efficiency and cost-effectiveness. While solar batteries can add independence, they aren’t always financially viable, so it’s essential to weigh the pros and cons based on your specific goals. Whether you’re looking to lower your energy bills or prepare for future expansion, careful planning will help you make the most of your solar investment.
