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  • Sarah Lozanova

What Is A Solar Inverter?



Although solar shoppers tend to be more interested in solar panels, the inverter is also critical. Proper selection of an inverter is essential for optimum energy production. For example, if a central inverter fails, the entire solar PV system can shut down. If the inverter is undersized, it can result in inverter clipping, where some electricity from the solar panels is wasted.


Solar panels are designed to generate renewable energy for 25 years or more. Many inverters do not last that long and need to be replaced during the lifespan of the modules. Also, the efficiency of the inverter has an impact on the total energy production of the solar array. Therefore, proper inverter selection is critical, especially on shaded roofs or complicated rooflines.


Therefore, selecting an inverter is a critical part of designing a solar energy system. Yet, many companies struggle with choosing the ideal inverter technology for each project. Let’s learn more about them to make equipment selection easier. Get solar permits, design, and engineering through the GreenLancer marketplace. Sign-up for free now.


How Do Solar Inverters Work?

Understanding the role of an inverter requires examining direct current (DC) and alternating current (AC) electricity. When sunlight hits a solar photovoltaic module, it creates a current of electricity. This current is DC power, which means the electricity travels in a single direction. Likewise, solar batteries supply DC electricity.


By contrast, most appliances, electronics, and lighting systems use AC power, which means that the electrons move in both directions, forward and backward. AC current is better for transmitting electricity long distances; for example, power lines use high-voltage AC electricity.

An inverter is found in both grid-tied and off-grid applications and converts the voltage from DC to AC. So, the inverter acts like a currency exchange allowing AC appliances to use solar electricity.


When selecting an inverter, it is critical to consider efficiency, wattage, and warranty. Most grid-tied inverters are more than 95% efficient under typical conditions and are sized in watts, just like the solar modules. When sizing an inverter, one of the most significant considerations is the capacity of the solar power system and solar irradiation in the local area.


If the inverter is undersized, it will clip power and some of the electricity that is produced from the solar panels will be wasted. This can reduce the total amount of energy generated from the system.


Solar panel warranties vary widely among manufacturers, and some provide the option to extend the warranty for an additional fee.


Different Types Of Solar Inverters Plus The Best Of Each

Installers have several different PV inverter types and equipment combinations to choose from. Often, it isn’t a good idea to take a one-size-fits-all approach with choosing a solar power inverter because some properties are best suited with one type over another, depending on a variety of factors.


Microinverters

These inverters are mounted on the solar panel itself and convert DC to AC voltage. Therefore, individual panels have their own unit. Microinverters mitigate the impacts of shading or an under-performing panel by enabling each one to operate independently.


Popular Manufacturers

Enphase is one of the most widespread microinverter manufacturers, and it recently released the IQ7 and IQ7+. APsystems microinverters are also highly regarded in the industry.


Pros

For installations with panels at different pitches or shading, microinverters can lead to considerably more energy production over the life of the solar system. Likewise, they can mitigate the impacts of an underperforming panel on the entire array. Microinverters also enable panel-level monitoring and they assist in NEC2017 rapid shutdown requirements.


Cons

Unfortunately, some installers don’t think they are worth the additional cost because they tend to cost more than a central inverter. Also, they are located on the backside of the module, so if one fails, a technician will have to go up on the roof to complete repairs.


String Inverters

This technology is also known as a central inverter, and the name says it all. Multiple solar panels are connected to one central inverter. When installing the solar system, each module is wired together into a string. And, multiple strings can be wired together with the same inverter.


Unlike microinverters which are attached to the modules, string inverters are often located on the outside of the home or business, in a basement, or in a garage. For some projects, especially large ones, multiple string inverters are used.


Popular Manufacturers

The Fronius Primo and the SMA Sunny Boy are some of the best inverters on the market.


Pros

If shading is not an issue and the property has simple rooflines, a string inverter without power optimizers is a good economical option. One advantage is that the units are often easier to access for repairs than microinverters.


Cons

One disadvantage of a string inverter is that if it fails, the whole system can stop producing. Likewise, one underperforming panel can have a disproportionate impact on the total system output. Unfortunately, string inverters do not allow panel-level monitoring without optimizers.


String Inverters With Power Optimizers

Some projects have solar panels that are mounted at different angles due to complicated rooflines. For other projects, panels are mounted at different azimuths. Sometimes, shading or snow can have a big impact on solar system power output, depending on the property and the climate.


In such cases, a string inverter alone might not get the maximum power possible from the system, and adding optimizers might be a good choice. Power optimizers are mounted on each solar panel to increase total energy generation and condition the power before feeding it to the inverter.


Popular Manufacturers

The SolarEdge HD Wave and the Huawei SUN2000L1 both manufacture string inverters with power optimizers, but the optimizers are optional with the Huawei unit.


Pros

Optimizers can boost energy production when the panels are mounted at different angles or shading is an issue. They can also assist in meeting NEC 2017 rapid shutdown requirements and enable panel-level monitoring.


Cons

Unfortunately, optimizers come at an additional cost, so a string inverter with optimizers costs more than one without. Also, the optimizers are located on the backside of the panels, so they can be difficult to access for repairs.


Solar Inverter Plus Battery Storage

Some inverters are specifically designed to work with solar batteries, either in an off-grid or hybrid capacity. Hybrid systems are connected to the electrical grid and can participate in net metering, but they can work independently of it during utility grid outages. These units have both a solar inverter and a battery inverter in one.


Keep in mind that some batteries come with built-in inverters and the capabilities of a hybrid inverter might not be needed. Conversely, you can use a hybrid inverter without battery storage. For example, some homeowners might want a solar system that is storage-ready, and they could add the battery bank later.


Popular Manufacturers

The Outback Power Skybox and the SolarEdge StorEdge inverters are highly regarded.


Pros

Having battery storage capabilities offers greater resiliency, especially during grid outages. These units perform two functions in one unit, eliminating the need for both a battery inverter and a solar inverter.


Cons

Some batteries come with a built-in inverter, making a hybrid inverter unnecessary. Also, adding a hybrid inverter and battery storage significantly increases the total cost of the solar installation.


How Much Do Inverters Cost?

Solar inverters range in price from about $1,000 to $2,600 for residential models. Many manufacturers produce units of various sizes, and the higher-wattage inverters cost more. Keep in mind that the federal tax credit does apply to the cost of the inverter.


How Long Are Inverter Warranties?

Most string and hybrid inverter warranties range between 5 and 12 years, and some have an option to extend. APsystems offers a 10- or 25-year warranty for its products and Enphase offers a 25-year warranty. SolarEdge and Huawei both provide a 25-year warranty on their power optimizers.


Finding The Right Inverter For Your Client

Finding the right inverter for a project depends on the property, climate, project budget, and goals. Understanding your client’s goals and the property can help shape equipment selection.


For example, if it is critical to keep the project budget low, despite some loss in long-term energy production, then a string inverter might be an excellent choice. If you have a client that wants to install a solar battery soon, a hybrid inverter is an appealing option.