How to Properly Size a Solar Panel System

Matt Keane
April 7, 2023

Deciding on the correct size for your solar panel system can seem daunting. We all want to make our homes more energy-efficient, and we've been there ourselves - wrestling with kWh usage, peak sun hours, and sizing calculations.

Our comprehensive guide simplifies this process by breaking it into straightforward steps covering every crucial factor in solar system sizing. Ready to harness the power of the sun? Let's demystify solar together!

Factors to Consider When Sizing a Solar Panel System

This paragraph will discuss how to properly size a solar panel system. When sizing a solar panel system, it is important to consider factors such as calculating your energy usage, determining your peak sun hours, and calculating the size of your solar system.

Calculate Your Energy Usage

First, You must calculate your energy usage to size your solar panel system properly. Here's how to go about it:

  1. Gather your electricity bills from the past 12 months. This provides an accurate record of your yearly energy consumption.
  2. Take note of the monthly kWh used, as shown on your bills.
  3. Add up these monthly totals to get the annual kWh usage.
  4. Divide this figure by 365 (the number of days a year) to obtain daily kWh usage.
  5. Factor in any anticipated changes in energy usage – perhaps you're planning to install an electric car charging station or add more occupants to your home.
  6. Use online tools for additional help – some websites and apps provide energy consumption calculators that can simplify this process.

Determine Your Peak Sun Hours

To properly size a solar panel system, it is important to determine your peak sun hours. Peak sun hours are the hours during the day when the sunlight is most intense and can generate maximum solar energy. This information is crucial in calculating the size and output of your solar system. Here are some key points to consider regarding peak sun hours:

  1. Check your location: The amount of sunlight received varies depending on your location. Different regions have different average daily peak sun hour values.
  2. Consider seasonal variations: Peak sun hours can also vary throughout the year due to weather patterns and seasons changes. It's important to consider these variations when sizing your solar system.
  3. Use online tools: Online resources and calculators that can provide data on average peak sun hours specific to your location, helping you estimate your system's potential solar energy generation.
  4. Consult with experts: Solar panel providers, such as SunPower, assist in determining peak sun hours and other factors contributing to accurate system sizing.
  5. Optimise placement: Properly positioning your solar panels can maximise their exposure to sunlight and increase the efficiency of your system. Factors like shading from nearby structures or trees should be considered when determining the best location for installation.

Calculate the Size of Your Solar System

To properly size your solar panel system, follow these steps:

  1. By dividing the number of days covered by the kilowatt-hours (kWh) used, you can calculate your average monthly energy usage.
  2. Estimate the amount of sunlight your solar panels will receive by considering factors such as location, shading, and orientation.
  3. Use an online calculator or consult a solar panel provider to determine the number of panels needed based on your energy needs.
  4. Consider the dimensions and weight of the solar panels based on the total wattage required.

Fine-Tuning the Estimated System Design

This section will discuss the steps in fine-tuning your estimated system design to ensure optimal performance.

Selecting the Right Mount Type

When selecting the right mount type for your solar panel system, it is important to consider factors such as the location and structure of your property. Choose a mount that is compatible with the design of your roof or ground area.

Ensure that it provides optimum sunlight exposure for maximum energy production. You can opt for a fixed or tracking mount, depending on your specific needs. Fixed mounts are generally more cost-effective and simpler to install while tracking mounts adjust the position of the panels throughout the day to capture more sunlight.

Consider consulting with a solar professional to determine which mount type will work best for your home or property. 

Contact BuildTech today if you're looking for professional consultation on how to properly size a solar panel system for Dublin's reliable and experienced building contractor team.

Choosing The Appropriate Solar Panels

When choosing the appropriate solar panels for your system, it is important to consider factors such as panel size, weight, and technology. Solar panels are available in different sizes and weights, with dimensions influenced by the total wattage required and the type of solar cell technology used.

Selecting panels that meet your specific energy needs and can be easily installed on your property is crucial. Choosing the right solar panels ensures optimal performance and efficiency for your home or garden solar system.

Calculating Solar System Output

To accurately calculate the output of your solar panel system, there are a few key factors to consider:

  1. Start by determining your home's average monthly kilowatt-hour (kWh) usage. This can be done by dividing the total kWh usage by the number of days covered.
  2. Take into account the amount of sunlight your solar panels will receive. This is measured in peak sun hours and varies depending on your location.
  3. Consider the efficiency and capacity of your solar panels. Different panels have varying efficiency levels, affecting their ability to convert sunlight into electricity. Furthermore, the capacity of your panels will determine how much energy they can generate.
  4. You may also need to factor in any fluctuations in energy production due to weather conditions or shading from nearby buildings or trees.

Choosing the Right Solar Equipment for Grid-Tie Systems

When choosing the right solar equipment for grid-tie systems, remember a few key considerations. From opting for American-made panels to evaluating the imported panel options, we'll guide you through finding the perfect fit for your solar power needs.

Learn more about selecting the right solar equipment for your grid-tie system.

Grid-Tie Systems With American-Made Panels

Grid-tie systems with American-made panels are an excellent choice for homeowners in Ireland looking to reduce their carbon footprint and save on electricity costs. These panels are known for their high quality, efficiency, and reliability.

Connecting the solar panel system to the grid can send any excess energy generated back to the grid for credit or sell back to the utility company. Homeowners can benefit from lower electricity bills and earn money through net metering programs.

Using American-made panels ensures that you support local businesses while enjoying all the benefits of clean, renewable energy.

Grid-Tie Systems With Imported Panels

Grid-tie systems with imported panels allow homeowners in Ireland to harness solar energy and reduce their dependence on traditional energy sources. These systems consist of solar panels manufactured outside of Ireland but still meet high-quality standards.

By connecting these imported panels to the grid, homeowners can generate electricity and sell excess power back to the utility company.

One advantage of using imported panels is that they may be more affordable than locally produced options. This cost-effectiveness allows homeowners to invest in a larger system or allocate funds for other aspects of their solar installation. Additionally, importing solar panels from reputable manufacturers ensures that homeowners have access to efficient and reliable technology for maximum energy production.

It's important to note that while using imported panels can be an excellent choice, it's crucial to consult with local suppliers and professionals familiar with Irish regulations and grid connection requirements.

They can help ensure seamless integration into the existing electrical infrastructure while adhering to safety guidelines.


Properly sizing a solar panel system ensures optimal performance and energy production. You can design a system that meets your needs by accurately calculating your energy usage, determining peak sun hours, and considering factors such as mounting and panel selection.

With online calculators and assistance from reputable solar providers like SunPower, homeowners in Ireland can confidently embark on their journey towards sustainable energy solutions with a properly sized solar panel system. 

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*FYI, parts of this blog post were drafted by artificial technlogy. But rest assured, it's been thoroughly researched, edited, reviewed and me & my team.

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