Microinverters or String Inverters?
What’s the scoop?
When comparing solar quotes for your home, there are many factors in establishing a final design and decision: annual energy consumption, available roof space, cost, and trust in your installer and manufacturers. These are the biggest factors our clients share when they go solar. We would like to add another variable that ought to be included:
Microinverters vs String Inverters.
Most clients don’t have a working knowledge of these similar but different technologies, and that’s OK!. Starting with a brief overview of how a solar system powers your home, we’ll establish why solar is such a GREAT technology, why this micro vs string inverter question ought to be a central design consideration, and how microinverters share the same qualities that make solar panels so successful.
Apr 27, 2023
What makes solar so great?
Solar modules produce Direct Current (DC) power and inverters manipulate that DC power to make Alternating Current (AC) power for use in the home as well as enabling the backfeed to the grid (Net Metering). The beautiful aspect of a solar system, which enables it to be adopted by homeowners worldwide, is that solar panels safely operate with no moving parts for over 25 years and are essentially maintenance free. Solar panels haven’t actually changed all that much from their original design - just slowly increasing in efficiency with manufacturing improvements over the years. They’ve changed so little because the modular solar approach that we know continues to be the most efficient, reliable, cost effective, and the safest power supply available. The technology just works, its simplicity is its success!
Microinverters vs. String Inverters - FIGHT!
The variable technology in the home solar system is the inverter. Inverters have consistently been improved upon with big design changes over the years; advancements centered on operating more efficiently, keeping up with electrical code standards, and reliability. Inverter warranties have improved alongside efficiency from one year, to two, five, ten, twelve and now to 25 years, matching most solar modules! There is no doubt that home solar systems are extremely reliable after the many advances in inverter technology
If Inverters are so great, then why choose Microinverters over String Inverters, and what’s the difference?
In a solar system with a string inverter, the inverter is the central command. All power flows in and out of a singular unit (depending on the size of the system, there may be two or three string inverters, but for most home applications, there’s just one). We call it a “string” inverter because the solar modules are connected to each other in “strings” of six to sixteen modules (give or take) before the power goes through the string inverter. This means high voltage DC power running across the roof, through the house and into the inverter. This much power flowing into one unit generates heat, which needs fans to cool and switches and toggles to open and close the high voltage DC circuits, isolating from the rest of the inverter. With Rapid Shutdown requirements, this adds even more moving parts and requires additional equipment to be mounted under the solar module, introducing additional points of failure. When working properly, however, a string inverter conducts a beautiful symphony, humming and clicking away as it wakes up, heats up and manages itself day in and day out.
All of these parts, though, can and do fail, and require replacing. One toggle switch failure will stop all of your solar production until it can be diagnosed, sourced, and replaced. As an installer, much less a client, waiting around for a toggle switch to be shipped during peak production months while an entire system is down is NOT fun.
Microinverters are mounted directly under each solar panel and directly connected to each other. The “central” command in a micro inverter system is really just another breaker panel like the one already in the home except it has solar circuits inside. Each microinverter is completely autonomous from the other microinverters. Because the microinverter only inverts one solar panel’s DC power to AC, there is no need for cooling, moving parts, or additional equipment for Rapid Shutdown. One microinverter for every panel also means no high voltage anywhere on the house - ever. There is also no singular point of failure, as redundancy is built into this system. If one microinverter stops working, it has no effect on any other microinverter’s output. Additionally, you can always add more panels in the future due to its modular nature (more lines may need to be run to the roof, but so long as your existing electrical system can handle the additional power, you’re good to go.)
With string inverters, expansion needs to be considered at the time of initial installation.
What characteristics do solar panels and microinverters share?
Built into a microinverter system is simplicity, adaptability, safety, and reliability. These qualities are amazingly similar to the qualities that make solar panels so exceptional. In fact, microinverters are the pathway that enhance the qualities of solar panels because they don’t add excessive complications that reduce the viability of the solar panel. With microinverters and solar panels you set it and forget it. If one were to stop working, it's a small fraction of total output and is easily replaced.
See what Enphase, the microinverter system that we employ, has to say about it.
