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Solar Inverters: A Beginner’s Guide

Apr 18, 2022

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Solar inverters are an often-overlooked bit of technology responsible for turning energy from the sun into usable electricity for your home and the utility grid. They’re also an important factor in the cost of a home solar array along with deciding how many solar panels your house needs.

Like most other aspects of solar power technology, inverters are evolving. This article provides some helpful information so you can understand the basics of inverters and make an informed choice in discussing components with a solar panel installer.

Why Do Solar Cells Need An Inverter?

When solar modules collect sunlight, it turns the sunlight into Direct Current (DC) power, the type of current used in batteries.

Most homes and appliances, though, run on Alternating Current (AC). That’s true whether the home is connected to the electrical grid — also known as grid tied — or if the home is off-grid. The inverter’s job is turning the solar energy from DC to AC for your home to use.

What Else Can A Solar Inverter Do?

Today, inverters can do much more than switch sunlight from DC to AC. They can also monitor your system’s output and keep homeowners informed about anything wrong with their system, such as individual panels that aren’t producing as much power as others.

Home solar owners can check this information from a smartphone app. In some cases, the inverter can also communicate directly with the utility company.

What Type Of Solar Inverter Will Work For My Home?

There are different types of solar inverters, just like you’ll find different types of solar panels. They all have some qualities in common, like efficiency and longevity, but there are some key differences as well.

 
While solar panels can vary widely in efficiency, inverters are closely matched regardless of brand and type. You’ll find most reputable inverters to be in the 97 – 99% efficiency range. Solar inverters aren’t expected to last as long as solar panels, which typically last 25 – 30 years and often carry long-lasting warranties. The industry-expected lifespan for inverters is 10 – 15 years.
 
Here are the main types of solar inverters and how they differ.

Central Inverter/String Inverter

Pros

Cons

● Low-cost option for simple layouts

● System size upgrades may require an inverter replacement


 

Central or string inverters have been around the longest. Energy from the solar panels goes to one inverter mounted on an external or basement wall. Central inverters are great for homeowners who have a simple panel layout and want a sturdy, low-cost inverter.

If one panel underperforms, it can reduce the performance of panels further down the string because all panels are connected to the same inverter. Also, if you decide to upgrade your system size in the future, you may need a more powerful inverter.

Microinverter

Pros

Cons

● Easy system upgrades

● Efficient for irregularly shaped homes

● System size upgrades may require an inverter replacement


 

Microinverters are small inverters mounted right next to each solar panel. They convert the DC power to AC on the spot.

For homes that are irregularly shaped or receive intermittent sunshine, microinverters can be a great solution. Plus, if you want to upgrade your system in the future, micro inverters typically allow you to add a few more panels without requiring a bigger, more expensive central inverter.

Hybrid Inverter

Pros

Cons

● Maintains battery charge with grid power when rates are low

● Startup cost

● Inefficient for shaded, complex roofs

 

Hybrid inverters combine two important functions for a solar system: they can serve as the inverter for the entire array, as well as the battery inverter. Even if you’re not considering adding storage to your system up front, a hybrid inverter could be a good choice if you plan to add it in the future.

 
They will convert AC to DC to charge up the battery using grid power, or convert DC to AC to power your home from your solar array. Essentially, hybrid inverters allow you to use grid power as a charger for a battery backup. This can be helpful for handling loads like electric vehicle charging at night, when your panels are not supplying energy.
 
The main disadvantage of hybrid inverters is initial cost. They also don’t work for shady, complicated roofs because they still convert DC to AC with a central device.

Power Optimizer

Pros

Cons

● Useful monitoring system

● Increased conversion efficiency

● Accessory expense on top of separate inverter purchase

● Not widely available

 

In addition to an inverter, some arrays can benefit from a power optimizer. Power optimizers, which are mounted on the back of individual panels, aren’t actually a type of inverter. Instead, they provide the maximum power point tracking (MPPT) from each solar module and increase the panel efficiency. MPPT helps determine the optimal output from each panel and the maximum amps into a battery.

With power optimizers, homeowners can get more conversion efficiency — meaning better ability to turn sunlight into power — even on partially shaded roofs. They can also monitor the production and status of individual panels. That said, power optimizers add expense to your system, and they’re not widely available because they’re relatively new technology. Also, they don’t allow you to increase your system size like microinverters do.

What Size Inverter Do I Need For Solar?

Let’s say you have a 6-kilowatt solar system. That means your inverter needs to have a maximum input energy of 6 kilowatts, right?

Not necessarily. It’s rare that your system will ever produce at its peak. You can save money with an inverter that’s under your panels’ peak. That’s why some solar panel installers don’t install inverters to handle the maximum.

That said, if you have any plans to make your home consume more electricity — getting an electric car or converting gas appliances to electric — you may want to get a more powerful inverter that would allow you to upgrade the system more cost effectively.

Choosing microinverters would also be a good way to plan for future solar system expansion, even if the initial cost per panel is higher.

What Happens If Solar Panels Produce Too Much Power For The Inverter?

It’s possible for solar panels to produce more electricity than your inverter is rated for. When that happens, you have solar panel clipping. The system simply won’t convert that solar energy into AC output. Yes, you’re wasting some potential electricity, but likely not enough to justify the cost of a more powerful inverter.

How Much Do Solar Inverters Cost?

Prices vary by the type and size of an inverter. In many residential systems, a central inverter will start at about $1,000. If you add power optimizers, you may spend $50 to $200 more per panel. On a 5 kW solar panel system, choosing microinverters could add $1,000 or more to the total cost.

Homeowners who are quick – and able – to take advantage of the Solar Investment Tax Credit (ITC) can also offset the cost of supersizing their central inverter or choosing new technology like microinverters and power optimizers. The ITC is only available for qualifying home solar arrays installed by 2023 unless Congress votes to continue the benefits. Consult a tax professional for advice and assistance applying for the credit.

The Bottom Line: There Are Inverter Options For Every Need

Whether you have a perfectly oriented roof with all the sunlight you need or a partially shaded roof with complicated design, there’s an inverter solution that will work for your home.

You can remove some of the guesswork by speaking with a Rocket SolarSM expert today.

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