How Do You Determine the Right System Size for My Home?

There isn't a simple formula. Many solar systems are sized using annual electricity usage and the amount of available roof space. Those are important inputs, but they don't tell the whole story.

The right system size depends on how your home uses electricity throughout the day and year, how much solar energy your roof is expected to produce, whether you're adding battery storage, your utility's rate structure, and what you hope to accomplish with your investment. That's why Sunbank analyzes your home's energy use hour by hour instead of relying on annual averages.

Why Annual Numbers Aren't Enough

Imagine two homes that each use 18,000 kWh of electricity per year. On paper, they appear identical. In reality, they could have very different energy needs. One family may be away during the day and use most of its electricity in the evening. Another may work from home and use electricity steadily throughout the day. One home may have large summer air conditioning loads. Another may have more consistent usage throughout the year.

Although these homes consume the same amount of electricity annually, the ideal solar and battery system could be very different. Annual totals are useful—but they hide the hourly patterns that determine how a solar energy system actually performs.

Why Hourly Analysis Matters

Electricity isn't consumed once a year. It's consumed every hour. Likewise, solar panels don't produce the same amount of electricity every day, and batteries are constantly charging and discharging as conditions change. To understand how a proposed system is likely to perform, Sunbank evaluates hour-by-hour interactions between:

• Your home's electricity usage
• Expected solar production
• Battery charging and discharging
• Seasonal weather patterns
• Electricity exported back to the grid

Looking at these interactions over thousands of hours provides a much clearer picture of how a proposed system is expected to perform than annual production estimates alone.

What We Evaluate

Our recommendations are built around three primary objectives.

Financial Impact. We estimate how the proposed system is expected to affect your electricity bills by analyzing when your home is likely to purchase electricity from the utility and when it will rely on solar or battery power. If your proposal clearly describes the purchase price or financing terms, we incorporate that information into our analysis whenever possible. If important financial details aren't disclosed or are too ambiguous to evaluate confidently, we'll explain what we know—and what we don't—rather than making assumptions.

Energy Utilization. Generating electricity is only part of the equation. We also evaluate how effectively your home is expected to use the energy your system produces. That includes estimating how much solar energy is likely to: Power your home directly, Charge your battery, Be exported back to the grid. This helps identify systems that appear oversized, undersized, or well matched to your home's energy needs.

Daily Resilience. For many homeowners—especially in hurricane-prone regions—backup power is one of the primary reasons to consider battery storage. Rather than asking, "How long will my battery last?", we ask a different question: "How much of each day can my home power itself during an extended outage?" By analyzing hourly production, consumption, and battery behavior, we estimate your home's Daily Self-Powered Resilience during different seasons of the year, with particular emphasis on the high-demand summer months when extended outages can have the greatest impact on comfort and safety.

What We Don't Estimate

Some parts of a solar proposal are controlled entirely by the installer. For example, changing the number of panels or batteries may affect:

• Equipment pricing
• Financing terms
• Dealer fees
• Promotional discounts
• Installation costs

Those changes vary from one installer to another, and they often aren't disclosed in enough detail for us to estimate accurately. Rather than guessing, Sunbank identifies opportunities that may improve your system's performance and encourages you to discuss those options with your installer.

Helping You Have a Better Conversation

Sometimes our analysis suggests that a different system configuration may better match your goals. For example, we may identify opportunities such as: Reducing the number of solar panels while maintaining similar electricity bill savings. Adding battery storage to improve resilience. Increasing system size to support future electricity needs. Better matching solar production to your home's usage patterns.

Those recommendations are intended to help you ask informed questions—not replace your installer's expertise. Your installer understands the costs of designing and building your system. Sunbank helps you understand how that system is likely to perform. Together, those perspectives lead to better decisions.

The Bottom Line

Choosing the right solar system isn't about maximizing the number of panels or batteries. It's about finding the right balance between financial impact, energy utilization, and resilience for your home. By evaluating how your home uses and produces energy hour by hour, Sunbank provides an objective analysis of how a proposed system is likely to perform—helping you make a more informed decision before you sign a contract.