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Choosing a Solar Inverter: Here is What You Need to Know

Solar inverters are what we may call the brain of a home solar system. All the critical operations take place here, such as direct current (DC) to alternating current (AC) conversion, performance monitoring, and serving as an interface for the grid. This makes choosing a solar inverter an important aspect of your solar journey.

Inverters come in various types with varying purposes, efficiencies, compatibilities, lifespans, and costs. Which one to choose and why?

Read on, as we will take discuss everything important you need to know about solar inverters to make an informed decision when choosing a solar inverter.

How to choose your solar inverter?

Not every solar inverter would work for your system. Some would work, but the output will be compromised. Others would give an excellent output but won’t be able to integrate with the grid electricity. This is because some inverters are more suitable for specific solar systems or homes with certain dynamics.

Here are six things to consider while choosing your solar inverter. 

1. Compatibility: Grid-tied, hybrid, or off-grid?

First of all, what type of solar system are you installing? If it is a grid-tied system, you would need a grid-tie inverter. Besides making solar electricity usable, it also allows a bidirectional electricity flow between your home and the grid. If your system is hybrid, i.e., connected both to the grid and batteries, you would need a hybrid inverter. They are a bit more complex, as they will also have to keep batteries in the loop.

Lastly, you would need a battery-based off-grid inverter if it is an off-grid solar system. You cannot install a grid-tied inverter for an off-grid system, as they cannot properly work with an off-grid system and vice versa.

2. Got shade on your roof?

Is your roof shade-free, or is there some shade? If there is no shade, string inverters will work fine for you. Depending on your system size, you would need one or two inverters.

But if there is shade on your roof, you should consider using a microinverter or a power optimizer system. Microinverters are installed on each individual solar panel and convert the DC power generated by the panel into AC power at the panel level. Power optimizers are also installed at the panel level and work in conjunction with a string inverter. They optimize each panel’s performance and allow the system to continue producing energy even if one panel is shaded.

Both options make up for energy lost due to shade on one panel—the system’s overall performance will be smooth.

Next Earth Solar Tip

Seasonal changes affect shading patterns. For example, during summer, a tree might have leaves and cast a shadow on a solar panel, while in winter it may not. Take into consideration different patterns while finalizing the type of your inverter system.

3. Is solar inverter efficiency a thing?

Yes—and it matters. Solar inverter efficiency means the ability of the inverter to convert DC into AC electricity. It is measured as a percentage and is determined by the ratio of the output power to the input power. The higher the efficiency, the more electricity is generated for a given amount of solar energy. For example, if the efficiency is 90%, 10% of the power generated by your solar panels is lost.

The best efficiency rating for a solar inverter is typically around 99%. But that’s not usually the efficiency—generally, it is around 93-96%. The rest is either lost or consumed by the inverter to keep itself up and running. 

Also, efficiency is not a straightforward number; there are two main types of efficiency ratings for solar inverters: peak efficiency and weighted efficiency. Peak efficiency refers to the highest efficiency achieved by the inverter under optimal operating conditions. This rating is usually measured at a specific input voltage and frequency. It is often used to compare inverters at a glance and is useful to know what’s the best efficiency the inverter can reach.

Weighted efficiency, of which European Efficiency and the more recent California Energy Commission (CEC) efficiency are two types, is a more realistic measure of efficiency. It takes into account the inverter’s performance over a range of operating conditions, including different input voltages and frequencies. This rating is used to give an idea of how efficient the inverter will be over time, and it’s the most commonly used efficiency rating in the industry.

When choosing your inverter, check both types of efficiencies, but make a decision based on the weighted efficiency.

4. The lifespan of solar inverter: How long do solar inverters last?

The lifespan of a solar inverter depends upon its type. String inverters last between 10 to 15 years—they are bigger, manage all the input, and are more prone to wear and tear. You will have to replace them at least once throughout your solar panels’ lifetime, which is around 25 years. Micro-inverters, on the other hand, last for more years and may match the lifespan of your solar panels, i.e., 25 years.

If you have an off-grid system, you would need an off-grid inverter. They have a shorter lifespan, usually up to 5 years. You will need to replace them at least four times in 25 years.

Several factors affect the lifespan of a solar inverter, the most important factors being temperature, humidity, capacity, and dust. Ensure that your inverter(s) is installed in a well-ventilated, cool, and dry place. Inverters that are exposed to extreme temperatures, high humidity, and dust are more likely to fail. Additionally, the quality of the installation and the regular maintenance of the inverter also play a role in increasing—or shortening—its lifespan.

5. Inverter sizing: What size inverter do you need for your solar system?

The size of your solar inverter will depend on the size of your solar panel system. Ideally, the inverter size should be equal to your system’s size—that is, a 6kW system should have a 6kW inverter. But it is, as we said, an ideal scenario. A general rule of thumb is to choose an inverter with a larger capacity than your solar panels’ maximum output. This will ensure that the inverter can handle the full output of your panels and not limit the system’s performance.

For example, if you have a 6 kW solar panel system, you should choose an inverter with a capacity of at least 6.5 kW. The extra capacity will make up for any losses in the system and allow the inverter to handle any temporary increases in panel output due to weather conditions. Plus, since the inverter is not 100% efficient, you will not lose any power lost during the conversion to AC output.

6. Price: How much does a solar inverter cost?

There is no definite answer to this question, as everything depends upon your system’s size, the type of solar system, and which type of inverter you choose. It also depends upon the inverter’s manufacturer.

But generally, inverters make up 6-8% price of the overall system. For example, if you are going to install a 6 kW system, the inverter may cost you around $1,200-$1,500. For a 10kW system, it may be around $2,200. The larger the system, the bigger would be the inverter, which will come at a higher price.

Some inverters may cost more, as they have added features like internet connectivity and monitoring. There are also other factors that affect the cost of a solar inverter, such as its brand, warranty period, etc.  

These are some of the things that affect the performance of solar inverters. Still confused? Worry not. Give us a call, and one of our solar advisors will assess your needs and suggest a solar inverter that would work perfectly for your home!

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