How to Size a Solar System: Step-by-Step Guide
Countless benefits of solar energy and the rising demand have convinced home and business owners to save on their electricity bills by going solar. The trend of shifting to solar power has become more popular these days. A huge percentage of US citizens have installed solar power systems on their homes and offices, and millions of others are planning to do the same in the near future.
It is a fact that a solar system can save you money on your utility bills, but a wrong-size system may lead to several issues, including system failure, unexpected costs, and inefficiencies. Therefore, before you invest in solar technology, understanding proper system sizing is crucial. In this article, you will learn how to size a solar system like a pro.
Solar System Basics: Types, Components, and Sizing Explained
A solar electric system consists of several components, including solar panels, an inverter, a charge controller, and batteries (optional). Panels capture sunlight and convert it into DC power. This DC power is then converted into AC power by a solar inverter.
Batteries are optional for grid-tied systems (also known as on-grid systems). However, they store excess energy for use during bad weather conditions, outages, or at night. At the same time, a charge controller is usually used in off-grid systems. It regulates the voltage and current from solar panels to batteries. This component keeps batteries away from overcharging. When we say sizing a solar system, it means sizing every component it has.
Let's now understand how different types of solar setups impact solar system sizing.
- Off-Grid Solar Systems: They are fully independent from the utility grid and produce all the energy required. Since they have to cover all power needs, larger systems have to be installed. They need oversizing to make sure that the system meets the energy needs during low-sun periods.
- Grid-Tied Solar Systems: They are linked to the utility grid. These systems send excess power to the grid and get a power supply from the grid at night or during low sunlight hours. The sizing of these systems does not aim for full independence; instead, it is based on reducing your utility bills.
- Hybrid Solar Systems: They have battery storage and are linked to the utility grid. These systems can deliver power at night or during power outages. The size of these systems is usually between off-grid and grid-tied solar power systems.
5 Simple Steps to Calculate the Size of a Solar System
It involves a series of steps, as listed and explained in detail below.
Step 1: Analyze Your Energy Consumption
Understanding the amount of power you use yearly, monthly, or daily is important. Your electricity bills can help you analyze your average energy consumption (kWh) in a month.
All you need to do is sum up the monthly consumption throughout the year and divide the answer by 12 to find the average monthly consumption. Then, divide the answer by 30 to calculate your average daily energy consumption. If you want to get more detailed insights, use smart meters or other energy monitoring devices.
Step 2: Consider Your Location & Solar Potential
You might be wondering what it has to do with your location. Right? Well, your geographical location shows the number of sunlight hours in your area or the amount of sunlight your solar panels will capture. The average daily number of hours when solar irradiance is maximum is called peak sun hours. During peak hours, solar panels perform effectively.
One thing you should consider when deciding on a place to install solar panels is that there is no shading from buildings, trees, or other tall objects. Moreover, poor installation angle, bird droppings, and dirt accumulation may reduce your system's performance.
Step 3: Calculate Your Daily Energy Consumption Requirements
You can easily calculate your daily power usage needs by dividing your daily consumption by average peak sun hours, as shown in the formula below.
Size of a solar system (kW) = Daily energy consumption (kWh) / Average daily peak sunlight hours
Suppose you consume 30 kWh/day and get six peak sun hours daily. In that case, you need a 5 kW solar system to meet your energy requirements.
Step 4: Consider System Efficiency Losses
No solar electric system is 100% efficient. The performance is usually affected by various factors, such as rising temperature, shading, and inverter losses. You can adjust losses depending on the system's efficiency.
Suppose your solar system is 80% efficient. In that case, you will multiply the system size by 1.2 to accommodate losses. If you don't add a buffer as an extra capacity to account for losses, your system may not be able to meet your energy needs fully.
Step 5: Find the Number of Solar Panels Required
When it comes to calculating the number of solar panels for your setup, you can divide the system size (in Watts) by the panel wattage (W). All you need to do is choose a preferred solar panel wattage. Suppose you have chosen a 400 watt panel. In that case, the number of solar panels can be calculated as follows.
Panel count = 5,000W / 400W = 12.5 ≈ 13
The equation above shows that if you want to install a 5 kW solar system with a panel rating of 400 W, you will need 13 solar panels to meet your power requirements.
Charge Controller / Inverter Sizing
Now that you know how to calculate your daily, monthly, and yearly energy consumption, and the number of solar panels required for any system. It is time to choose the correct size solar charge controller or inverter for your system.
While choosing a charge controller, never forget to match its ratings with the voltage and current of your solar panels. MPPT controllers are good, as they are more efficient than PWM controllers, but are expensive at the same time.
Similarly, while selecting a solar inverter, make sure that its rating matches the solar array output. Ideally, the inverter rating should slightly exceed the total array output of your solar system.
Battery Sizing (Optional)
As the header shows, battery storage is optional in grid-tied systems. It means you can install grid-tied solar power systems without batteries. On the other hand, the battery storage is a key component of hybrid and off-grid solar systems, as it stores excess energy.
If you live in a completely off-grid environment, you should consider solar systems with enough battery storage to fulfill your energy needs. Similarly, if you live in an area that faces frequent power outages, bad weather conditions, or a frequently cloudy atmosphere, install solar systems with batteries as a backup source.
When it comes to calculating the right battery size for your system, the formula below will lend you a helping hand.
Battery size (kWh) = daily use x days of autonomy / (battery efficiency x depth of discharge)
Suppose your daily energy consumption is 20 kWh, and you need 3 days of autonomy with a battery bank that has 90% efficiency and 80% depth of discharge. In that case, the battery size would be:
Battery size (kWh) = 20 x 3 / (0.9 x 0.8) = 83.3 kWh
It means you should have a battery bank with 84 kWh capacity.
Additional Factors to Consider While Sizing Your Solar System
Apart from analyzing and calculating your energy consumption (kWh) and considering your location and solar potential, there are some other things to consider as well. Let's have a quick look at some of them.
- Seasonal Variations: Don't forget to consider this factor, as your system may perform differently in different seasons. Less sunlight decreases the overall performance of solar systems during winter.
- Roof Space: Make sure you have enough space on the roof while sizing a solar system.
- Incentives and Local Permits: Ask your utility company and municipality about the permits and licenses required to install a solar setup on your site.
- Net Metering: Consider installing a net meter on your location to ensure the excess energy goes to the grid and the grid supplies you with power when the solar system does not produce electricity.
- Future Expansion: If you have a plan to expand the system in the future to accommodate your increased energy requirements, consider it while sizing your solar system.
Trusted Help for Sizing Your Solar System
Join Renogys Electrician Referral Program - a unique opportunity for certified electricians to expand their business with trusted solar solutions. Rather than recommending electricians to customers, Renogy invites professionals to introduce high-performance solar products to their own clients. Partners gain access to industry-leading tools, resources, and competitive rewards for every successful referral. It's a smart way to grow your services and align with a brand trusted by professionals nationwide. Join today and help lead the shift toward smarter, cleaner energy.
When choosing solar components, professional trust matters. Renogy's products are not only popular with homeowners but also trusted by electricians for their performance, durability, and support. This endorsement offers added confidence when making key system decisions. To simplify installation, Renogy's Electrician Recommendation Program connects you with qualified, vetted electricians familiar with Renogy systems - ensuring efficient, correct setup. Whether you're sizing your system or preparing for installation, Renogy links you to reliable products and professionals you can count on.
Final Thoughts
Wondering how to do solar panel sizing or solar system sizing? A couple of factors play a key role in determining the correct size for your system. They include your daily, monthly, or annual energy consumption, geographical location, solar potential, roof space, net metering, and performance variations during different seasons.
If you need assistance with sizing a solar system, the discussion above has presented a comprehensive step-by-step guide. It talks about sizing solar panels, an inverter, a solar charger controller, and the battery storage. If you need cost-effective and reliable solar equipment that lasts longer, explore an unmatched collection available at Renogy.
FAQs about Sizing Solar System
Is sizing an off-grid solar system different than sizing a grid-tied system?
Yes, both systems need different sizing strategies. Off-grid solar power systems should be larger to meet all of your energy requirements. They must have extra capacity to store excess energy in batteries and for cloudy weather. In contrast, grid-tied solar systems can be smaller, as they have the utility grid as a backup source of energy.
Can I size a solar system without batteries?
Yes, you can size a grid-tied solar system, as it does not need batteries as a backup source of power. You can consider local solar production estimates and your average daily/monthly electricity usage. Though a grid-tied solar system does not give you full independence, it significantly reduces your electricity bills.
Can I trust online solar system size calculators while sizing my home solar system?
Well, you can get some good estimates from these online calculators, but they may not consider all factors, such as appliance efficiency, local weather conditions, shading, and consumption changes in the future. Therefore, it is always recommended to have a professional site assessment to ensure precise system sizing.
