Microinverters vs. string inverters: Which is right for you?

Did you know inverters are just as central to a solar installation as solar panels? Solar panels generate a type of electricity your home can't use right away, called direct current (DC) electricity. Inverters convert the DC electricity into alternating current (AC) electricity, which powers your home.

Choosing the right type of inverter for your solar panel system can make a big difference in its cost and performance. Usually, your installer will recommend a certain type or brand, but being an informed shopper can help ensure you're getting the right equipment.

There are three main types of solar inverters: string inverters, optimized string inverters (power optimizers + string inverters), and microinverters. We'll help you figure out which one is best for your solar panel system.

Centralized DC to AC conversion

• Easier system maintenance with no electronics on the roof

• Most affordable option

• Only offer string-level monitoring

Solar companies have used string inverter technology for decades. It's an incredibly reliable, tried-and-true technology and is the most affordable option available today. But it's not the best choice for certain types of installations.

In a string inverter setup, an installer will arrange your solar panels into groups connected by "strings" (hence their name!). You can connect multiple strings of panels to a single, centralized inverter, which transforms the DC electricity produced by the panels into usable AC electricity for your home or business.

Modern solar inverter and panel technology allows individual panels to continue producing power even if a part of the panel is shaded, but without module-level power electronics, string inverters can only optimize power output at the string level, not at the individual panel level. So, string inverter systems aren't always the best solution for homes prone to shading throughout the day. However, their ease of installation and lower prices make them attractive to homeowners and installers.

One of the most common reasons individual solar panels produce less power (or stop producing power altogether) is shade from nearby objects. If your roof experiences shade throughout the day or in certain seasons, you could either remove the source of the shade (e.g., cut down a tree) or install the panels in a sunnier space (e.g., ground mount or carport installation).

Centralized DC to AC conversion + panel-level optimization

• The power output of each panel is optimized independently

• Provide both system and panel-level monitoring

• Future system size increases may require an additional central inverter

Power optimizer systems offer many of the same benefits as microinverters and are often a compromise between microinverters and standard string inverters.

Like microinverters, systems with power optimizers have an individual optimizer component at each panel, the module-level power electronics (MLPE) component. They reduce the impact of panel shading on system performance and offer panel-level performance monitoring.

However, instead of converting the DC electricity to AC electricity at the panel site, they "condition" the DC electricity and send it to a string inverter for conversion.

If your roof experiences shade during the day, the panel-level optimization afforded by power optimizers often results in higher system efficiency than using a string inverter alone.

Panel-level DC to AC conversion and optimization

• The power output of each panel is optimized independently

• System size can be expanded easily in the future

• Electronics are all located on the roof

Microinverters, another form of MLPEs, are by far the most popular type of inverter on EnergySage, even though they're also usually the most expensive.

Microinverters convert the DC electricity from your solar panels into AC electricity on your roof without a separate string inverter. Installers usually mount the microinverters onto the back of the solar panel, but they can also place them next to the panel on your solar racking system.

While power optimizers aggregate the electricity from your panels and send it to a string inverter for the DC to AC conversion, microinverters make the DC to AC inversion right at each solar panel.

As a result, like with power optimizer systems, microinverters also allow you to monitor the performance of individual solar panels.

If you have a south-facing roof with a single plane and no shade, save some money by choosing a string inverter.

Unfortunately, most roofs aren't that simple, so you'll probably want some level of panel-level optimization. But it might not need to be 1:1 microinverters or optimized string inverters: Some microinverters will provide power to four panels instead of just one, saving you some money.

Why panel-level optimization is often worth it

Here are some reasons you might choose inverters with panel-level optimization.

1. They help improve performance for solar panels on complicated roofs or roofs that experience marginal shading during the day.

2. They can monitor the performance of individual solar panels, meaning you can assess the number of kilowatt-hours (kWh) one solar panel in your array produces versus another.

3. For microinverters, if one stops working, that doesn't ruin your entire system's performance

Microinverters vs. optimized string inverters: How do they differ?

Microinverters and optimized string inverters provide many of the same benefits, but they're not the same things. Here are the biggest differences:

1. Microinverters convert electricity at the panel level

Microinverters convert DC energy into AC energy right at the panel site. Power optimizers sit behind a solar panel, but they don't convert the electricity independently.

Instead, optimizers "condition" the DC energy and send it to a central inverter that finishes the conversion process. The conditioning process fixes the voltage of the DC energy so that the centralized inverter can more efficiently convert it to AC energy.  However, if your central inverter breaks, it takes down your whole system.

2. Microinverters often come with better warranties

Both microinverters and power optimizers come with 25-year warranties. However, while warranties cover optimizers for 25 years, the centralized inverter they pair with often has a shorter warranty (typically 10 or 12 years). Installers sometimes offer an extended warranty on the central inverter, either as part of their package deal or at an additional price.

It's also important to closely examine what a company's warranty terms include (and what they don't!). Does the company cover installation labor, replacement, and shipping parts? And what is the claim process like for getting a warranty processed? These are essential considerations when choosing the type of inverter to install on your property.

3. It can be easier to fix or replace optimized string inverters

Over the lifetime of microinverters and power optimizer systems, you need to consider if and how many times they'll fail, as well as the impact of an unlikely failure on the production of your solar panel system.

If an individual inverter fails, replacing a microinverter or a power optimizer on a roof will likely cost more than replacing a string inverter on a ground-level wall, given the labor required to access and work on your roof. However, no need to worry if your inverter has a strong labor warranty!

4. Microinverters can limit your battery setup

Both microinverters and power optimizers are compatible with battery storage. But, depending on whether you want a DC or AC-coupled battery solution, you may need to use a particular type of inverter. Microinverters typically only work with AC-coupled batteries. If you're considering battery storage, talk to your installer or electrician about which inverters work best with your battery of choice.

Ultimately, you want to pick an inverter that enables your solar panel system to perform well without breaking the bank. Talking to your installer about the inverters they offer and what they think will be the best fit for your system is the perfect place to start.

It's important to remember that microinverters and optimizers aren't the only available options. String inverters are the way to go if you're looking for the most wallet-friendly option and have a south-facing roof with little shade. But if your roof is more complicated, microinverters or power optimizers could significantly increase your savings with solar down the line.