Planning a solar project has many facets and fine points to consider. From layout design to module selection, every choice will determine the value that is ultimately derived. In this blog we will address how to select an inverter type that will bring the most value for your project.
What are solar inverters?
Inverters are devices that “invert” the direct current (DC) energy generated by the solar panel to alternating current (AC) electricity that the grid and your home or building runs on. Inverters are a staple in all grid-tied systems, but their functionality, space requirements, and warranty characteristics vary depending on the type you choose. Having a basic knowledge of these industry offerings will help you achieve the highest value for your project.
Before we examine the types of inverters available for residential and commercial installs here are some definitions you should become acquainted with:
Anti-Islanding / Grid-Tied Inverters – These are inverters that cannot put out their own AC sine wave but rather they mirror the grid’s AC sine wave and only work when utility power exists.
Multimodal Inverters – Sometimes called Bimodal Inverters, can operate in parallel with the grid and they can also put out their own AC sine wave if the grid goes down – these are most commonly used with battery backup.
Hybrid Inverters – Such inverters allow for integration with more than one power source. For example, a propane or natural gas generator can be connected to a hybrid inverter when the solar array cannot output enough to meet loads or when batteries have been fully depleted.
Now that we know a little bit about what inverters are capable of, let’s look at the three largest categories for residential and commercial application: String Inverters, Power Optimizer Inverters and Micro Inverters.
String Inverters
String inverters have a large potential impact from shade, soiling and module mismatch. They are best suited for unshaded, ground mount applications or commercial rooftop applications.
An example of a common string inverter on the market is a SMA Sunny Boy (right). Standard grid-tied string inverters will drive the cheapest cost for an install.
Other examples include Sol Ark and Outback inverters. These Multimodal & Hybrid inverters offer unique robustness for storage applications and give the option to install solar now and a battery later, AC or DC coupled.
Additional considerations for string inverters:
- String inverters need an additional product to comply with the NEC rapid shut down requirement if installed on a roof
- One drawback is that monitoring of these systems is only as granular as the string level, i.e. you won’t see the individual panel output
- Industry average: 10 year warranty
Power Optimizers (SolarEdge)
Power optimizers are DC to DC connectors that optimize voltage and current. This bolsters production as compared to standard string inverters and reduces the impact from shading. Power optimizers also comply with the rapid shutdown requirement for rooftop systems.
Additional considerations for Power Optimizer inverters:
- Optimizers are most commonly applied as one unit under each solar module
- SolarEdge is the biggest manufacturer of power optimizer style inverters
- They offer a 25 year part and labor warranty on optimizers, 12 part and labor on inverters (extendable)
- SolarEdge boasts the industry highest efficiency at 99% efficient in the conversion from DC to AC power
- Module-level monitoring – allows for easy system troubleshooting
- Only specific inverter models allow for DC-coupled storage integration (multimodal) – the majority of their product line is grid-tied inverters and can work with AC coupled storage like a Tesla Powerwall
- Have car charging integration available – “Solar Boost” mode allows for DC to DC charging faster than a standard level 2 home electric vehicle charger
Micro-inverters (Enphase)
Micro-Inverters are applied under each solar module, inverting on the roof as opposed to at a central inverter, most commonly near the utility meter. This negates the need for space to hang the central inverter, a commonly overlooked benefit. A good example are Enphase micro-inverters.
Additional considerations for micro-inverters:
- “No single point of failure.” This means that if one inverter fails, the rest of the panels will still work. On the contrary, if a central string inverter fails, the entire system is out of commission until it is rectified
- Microinverters have a lower input voltage which increases production in the early morning and late evening. Enphase estimates this would add +-15 minutes of additional production AM & PM
- Micro-inverters can be looked at as “safer” because they are inverting at the roof. When inversion occurs at the roof, lower voltage AC power runs down to the connection. String or optimizer inverters will run DC currents from 300-600 volts down to the inverter
- These are grid tied inverters, non multimodal and non hybrid, meaning you can’t connect DC coupled batteries or interface this system directly with your home generator
- Power is inverted at each panel, so shading issues only affect the panel shaded and not the whole string.
- Enphase micro-inverters offer a 25 year part warranty and 2 year labor warranty
All UL listed inverters on the market today include:
- Corresponding consumption monitoring equipment – You can track the power your home or business is using and generated
- Web based monitoring platform – system production can be monitored on web based or app based platforms
In summary, inverter selection is an important determination in order to get the most value out of your solar system. Each type will offer different value streams, bells and whistles, but they all accomplish the same task of transforming DC power to AC. While there are many important considerations when selecting your system’s inverter, you can rest assured Michigan Solar Solutions will help you design the best solution for you. Not sure what inverter selection is best for you? Give us a call at (248) 923-3456.
If you or another business is interested in having an undeniable impact on your triple bottom line give us a call for a free consultation to see if solar is right for you! Call (248) 923-3456 or request a Free Online Solar Analysis for Your Business.
Michigan Solar Solutions is a commercial and residential solar installer and electrical contractor that has served the lower peninsula of Michigan since 2007. We have installed thousands of panels and have a happy customer near you, check out what our customers think of us on Guild Quality.