Comparing micro inverters vs string inverters, plus other inverter types
In our previous article about how solar inverters work, we introduced you to string inverters, microinverters, power optimizers, and hybrid inverters. All these types of systems convert the DC electricity your solar panels make into AC electricity your appliances use.
In this article, we’ll discuss the pros and cons of micro inverters vs string inverters, as well as offer guidance on how to choose the best type of inverter technology for your home.
Comparing different solar inverter systems
When it comes to small scale solar PV inverters for grid tied systems, there are four main options available:
- String inverters
- Power optimizers tied to string inverters
- Hybrid inverters
In this section we provide an overview of each, discuss their pros and cons, and highlight what type of home each is best suited for.
What is a string inverter?
A string inverter is a standalone unit, typically installed close to your fuse box and electricity meter and creates alternating current (AC) from strings of panels. There is typically only one, or possibly two, string inverters on each residential solar panel system.
Pros and cons of string inverters
Pros: The main advantage of a string inverter is that you only need one of them. If anything is going to fail in a solar system, it is likely to be the inverter. Replacing it is relatively simple.
Cost is another advantage, as single string inverters are usually cheaper than installing other types of inverters.
Cons: In string inverter setups, electricity output is dependent on the panel that is performing the worst. String inverters will not perform well with panels oriented in multiple directions or if partial shade is an issue.
Adding onto your solar system at a later date can also be more difficult and costly with string inverters, as panel sets need to be sized well to each string inverter.
Best roofs for string inverters
If you have a roof with consistent southern exposure, and you know you’re not going to be adding onto the size of your system in the future, string inverters are an excellent, affordable choice to pair with your string of solar panels.
What is a microinverter?
Microinverters perform the same basic function as a string inverter but are installed underneath each panel on your roof. Each of these microinverters is about the size of an internet router.
The big difference is that a solar panel installation with microinverters will have the same number of microinverters as there are solar panels.
Pros and cons of microinverters
Pros: Microinverters take full advantage of the production capability of each individual solar panel, regardless of shade or orientation to the sun. This ensures maximum production of AC electricity flows to your fuse box and electric grid.
Your solar system can also be easily expanded at a future date with microinverters, since the DC to AC conversion occurs at the site of each panel, and the system need not be paired exactly to the capacity of a standalone inverter.
Microinverters come with relatively long 25 year warranties, a term length similar to your solar panels themselves.
Finally, microinverters allow you to monitor total system performance and the energy generated by each individual solar panel.
Cons: Microinverters are relatively expensive, since they need to be affixed to the back of every single panel. They typically cost $1,000 or more than a string inverter on a standard 5kW residential solar installation.
Best roofs for microinverters
If your solar system needs to face multiple angles (i.e. - some panels facing south, some east, and some west), you have shading issues from trees or a large chimney, want to squeeze the most electricity out of a smaller roof, and/or are leaning toward expanding the size of your PVok system at some point down the road, microinverters are the way to go.
What are power optimizers?
You can think of power optimizers as the little cousin of microinverters. Like microinverters, power optimizers are affixed to the back of every solar panel in your array. However, DC is not converted to AC behind every panel.
Instead, the DC electricity is conditioned, cleaned, and voltage-matched to the utility grid to ensure maximum power is generated by each panel. The power is then sent along to a smaller string inverter to convert DC to AC.
Pros and cons of power optimizers
Pros: The main advantage of power optimizers is their ability to harvest the maximum amount of DC electricity from every panel, regardless of roof orientation or shade.
Cost is an advantage over microinverters, as power optimizers are more economical.
Battery backup systems pair extremely well with power optimizers. Since batteries operate in DC, you can connect them directly to your “power optimized” solar panels without AC power conversion losses.
Cons: If you’re thinking about expanding the size of your solar power system at a later date, power optimizers are not the best option. The string inverter paired to your optimizers still needs to be sized to suit the size of your installation.
Best roofs for power optimizers
If you’re looking to upgrade your home with a battery backup system, you have multiple roof orientations to site panels on, and you know you’re not going to be expanding the size of your solar array, power optimizers paired with a string inverter are a solid choice.
What are hybrid solar inverters?
Hybrid solar inverters assume you are going to install a battery backup system alongside your solar panel installation. They come with DC inputs for your panels and batteries, and AC outputs for your fuse box and the grid.
Hybrid inverters are also equipped with a charge controller, to determine when to draw power from the grid to your battery, and to detect when your battery is full and route your power back to the grid.
Pros and cons of hybrid solar inverters
Pros: Hybrid inverters are more affordable than power optimizers or microinverters, and they add some peace of mind knowing you are able to easily add a battery system at some point down the road.
Hybrid inverters also allow you to take advantage of time of use (TOU) rates, to smartly charge your battery from the grid when it is the cheapest to get.
Smart hybrid inverters communicate well with the grid, and enter into a standby mode instead of switching off entirely if a disturbance is detected. The system can then turn itself back on, potentially saving you a lot of money if you happen to be on vacation.
Cons: Adding batteries to your existing solar system is relatively straightforward, even without a hybrid inverter. Also, they aren’t the best for system expansion ease, nor are they ideal for roofs with multiple directions to site panels on.
Best roofs for hybrid solar inverters
Hybrid inverters are a great choice if you’re looking for an affordable way to pair your solar panel system with battery resilience. Integrated features like a smart charging controller and multiple dc and ac inputs and outputs make it an easy upgrade.
Battery backup systems and inverter selection
If you are considering adding batteries to your home solar system, it’s important to note that any inverter type we discussed above can be compatible with your setup with an AC battery.
While power optimizers paired with DC batteries are the most efficient and elegant way to do the job because there are minimal losses due to DC to AC conversion, an AC battery is a perfectly reasonable way to go. The popular Tesla Powerwall 2 is an AC battery and it comes with an integrated inverter.
Comparing inverter types: weighing your options
When shopping around for a solar panel inverter, you may be prioritizing cost over warranty length, ease of expansion over battery readiness, and so on. In the below table, we’ve broken down each inverter type by what type of needs a customer might be looking for.
|Lowest cost||String inverter|
|Panel monitoring||Microinverter or Power optimizer|
|Battery readiness||Hybrid inverter or Power optimizer|
Which inverter type is best for your home?
When it comes to selecting the right type of inverter for your home solar panel system, keep in mind these three main considerations: Cost, shade tolerance, and ease of system expansion.
If you have a clean southern exposure and know you won’t be increasing the size of your solar system anytime soon, a string inverter is a great, affordable option. On the other hand, if you’d like to expand your system at some point and have challenging shading issues, microinverters are the way to go.
If you know you’ll be installing a battery backup system in addition to your panels, we recommend power optimizers for optimal efficiency. If you’re on more of a budget, consider a hybrid inverter instead.
Next → Solar inverter reviews
Author: Andrew Sendy | Home Solar Journalist
Andy is deeply concerned about climate change but is also concerned about cost of living pressures on American families. He advocates for solar energy and solar battery storage only to the extent that they make financial sense for homeowners. He is not affiliated with any particular solar company in the United States.