String inverters and microinverters convert direct current (DC) power generated by solar panels into alternating current (AC) electricity for safe transport to your home or the energy grid.
Having either a set of microinverters or a string inverter (or multiple string inverters, depending on the installation) is necessary for any solar energy system. When trying to choose one over the other, it can be challenging to know exactly what is right for your installation.
Although we previously touched on the differences between microinverters and string inverters in our guide to solar inverters, in this article, we will break down these two technologies piece by piece, to help you make an informed decision about your home’s renewable energy needs.
The Differences Between Microinverters vs String Inverters
Choosing a string inverter or a microinverter-based system may influence the overall costs, performance, and return on investment of your solar installation.
To begin, let's look at microinverters vs string inverters from a purely functional perspective.
Microinverters are classified as Module-Level Power Electronics (MLPE) meaning that they are installed at the “module” or solar panel level. For every solar panel in your array, you will have one microinverter installed to process its electricity production.
On the other hand, string inverters are used to process solar power from multiple panels at once. String inverters are also known as central inverters, and work by connecting “strings” of panels that are wired together into one central location where the DC/AC conversion takes place.
The physical size of a microinverter, as the name implies, is much smaller than that of a string inverter. Typically tucked away on the underside of your solar panels, microinverters usually operate while hidden in plain sight below a rooftop array.
Although it is rarely a problem for most residential properties, string inverters do require more space than microinverters, as they are physically larger and must be installed in a well-ventilated outdoor area. In instances where the exterior wall or yard space is extremely limited, microinverters could eliminate the need for a difficult string inverter installation.
When comparing microinverter vs string inverter efficiency, in full sunlight conditions, studies have shown that there are no performance advantages between the two. With that said, microinverters are generally seen as a more efficient technology when considering the limitations of string inverters to perform in a few unique circumstances.
Without included power optimizers (another MLPE, which we will go into more detail about later) the total power output along strings of solar panels can be significantly reduced in shaded conditions, even if that shade is limited or sparse. This is due to the fact that the output of individual solar panels wired into a string inverter may be limited by the lowest-performing panel in each string.
As the saying “a chain is only as strong as its weakest link” implies, one shaded, dirty, or damaged solar panel in a basic string inverter system can dramatically lower the total output potential of its neighboring panels.
Both microinverters and string inverters can be purchased with life expectancies and warranty periods extending 20 years and more. When looking at all of today’s technology, however, most microinverters are expected to last longer than average string inverters, and multi-decade performance is much more common for MLPEs.
Today’s industry standard for a string inverter warranty period is about 10 years. Knowing that most solar panels last 25 to 30 years, this means that a string inverter is more likely to require replacement midway through the lifespan of your solar system, compared to a set of microinverters that have 20- or 25-year warranties.
While under-panel placement may give microinverters an advantage in terms of ease of installation, things do get a bit more complicated when it comes to system maintenance.
Replacing a string inverter is generally a seamless process that rarely requires excessive time or labor. When installed on the ground level, maintenance personnel can usually walk up to the necessary components and swap out the old for the new in a short amount of time.
On the other hand, with a microinverter system, a part replacement usually requires access to the rooftop solar array, and may require a worker to temporarily uninstall the panel on which it is mounted.
Although modern microinverters are extremely reliable, the quantity of the equipment (i.e.16 microinverters vs 1 string inverter) does make it more likely that a malfunction could occur and lead to temporary system downtime. With that said, microinverters' independent functionality can also prevent failures from impacting the performance of other panels within the system.
Cost and Value
In terms of cost, you can expect to pay more upfront for a microinverter-based system than a solar array with a central string inverter. Even when adding power optimizers to your string inverter, a microinverter system is still likely to be more expensive.
When looking at long-term value, however, the cost vs the ROI of microinverters may tell another story for homeowners going solar. If a string inverter must be replaced midway through the panels’ lifetime, new string inverter costs outside of a warranty period may add to the total system cost.
On a property where the output efficiency of microinverters is much higher than string inverters, it may also be possible to make up the premium costs of adoption by generating more solar power overall, and avoiding additional utility expenses.
For a string inverter system to operate efficiently, all of the panels along each string should be exposed to similar sunlight conditions throughout the day, producing roughly the same amount of solar power in each moment.
Although this may not be a problem for homes with large roof faces, or on ground-mounted solar panels, buildings with complicated roofs and limited installation space may be better suited for a microinverter-based system.
If your roof faces in many different directions or your panels are partially shaded throughout the day (from trees, building features, etc.) micro inverters can increase your total solar power output potential.
After years of solar energy production, if you decide that you need more panels, having a microinverter-based system vs a string inverter will make it easier to expand your energy capacity.
With many different sizes available, string inverters are usually installed to process the approximate amount of electricity that a complete system is expected to produce. Therefore, if you would like to add more solar panels to a central inverter system, then you usually need to upgrade your inverter as well.
Separately, the independent operation of microinverters may allow you to add new solar panels (and microinverters) later on, without any additional equipment upgrades required.
Microinverter vs Power Optimizers
As two different module-level power electronics (MLPEs) microinverters and power optimizers are essentially designed to deliver the same results. Both technologies help capture the individual performance of your solar panels when separate panels are generating electricity at variable efficiencies due to direction, shading, damage, or other variables.
If you could benefit from MLPEs (i.e. your roof is partially shaded) choosing between microinverters or power optimizers installed with your string inverter may not critically affect your potential system performance, or your return on investment. Today, both technologies are commonly seen on rooftops across the country, and your installer may favor one system design over the other based on price, availability, and personal preferences.
To wrap up this guide to string inverters vs microinverter vs power optimizers, here are three questions that people often ask:
- Are microinverters better than string inverters?
- Although better is certainly a strong word, microinverters are generally more efficient than string inverters for installations with variable sunlight conditions. When equipped with power optimizers, however, string inverter systems can closely match the individual panel performance of microinverters.
- Should I install microinverters or a string inverter?
- Your choice between inverters or microinverters may be based on your property conditions or available resources. With a roof or yard that receives a consistent amount of direct sunlight, either technology will work just fine. If you have an excessive number of multidirectional roof faces or heavy roof shading, you may need to consider microinverters or power optimizers to maximize your solar production.
- Are microinverters worth it?
- Although everyone's investment is going to look a little bit different, microinverters are often worth it for home solar energy systems. By collecting the maximum production from each individual solar panel, the additional expenses of microinverters may be recovered through additional power generation.
How To Choose Between Microinverters and String Inverters
Ultimately, the decision between microinverters and a string inverter must be based on the individual factors of your installation. From the shape of your roof to the amount of space and shade on your property, you can work with your solar designer directly to weigh the pros, cons, expenses, and expected paybacks when installing a string inverter (with or without power optimizers) or a set of microinverters with your solar panels.
To begin the journey to your best possible solar installation, get an estimate of your savings with Palmetto today.