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Inverters are devices that turn DC (direct current) into AC (alternating current). Electricity from solar panels are DC while most appliances run on AC, so inverters are a necessity. But do you need a solar inverter or microinverter?
A microinverter is a type of solar inverter that is installed under a solar panel. The term solar inverter applies to all inverters designed to work with solar panels.
What is a Solar Inverter?
A solar inverter is an umbrella term for any type of inverter that converts solar panel direct current (DC) into 120/240V alternating current (AC).
Solar inverters differ from regular inverters because they are designed to work specifically with solar panels. Not all regular inverters can convert DC from solar panels. Not all solar inverters can handle UPS and other devices.
Why Solar Panels Need Solar Inverters
Solar panels produce direct current, while most appliances depend on alternating current. Without an inverter, you won’t be able to power your home with renewable energy.
When sunlight reaches a solar panel, the energy is turned into direct current. The solar panel transmits this current into the inverter. A good example of this is the Renogy 3000W pure sine wave.
The inverter absorbs the current and sends it into a transformer. Inverters do not actually change DC into AC. What it does is send the direct current through multiple transistors in such a way the transformer assumes it is alternating current.
Once the process is complete, the current is sent to the appliances. All of this happens quickly so we barely notice it, but a lot goes on before appliances get powered up.
I want to add that where you install a solar inverter makes a huge difference in efficiency. If you’re undecided yet, check out my detailed guide on where to install a solar inverter.
How Solar Inverters Differ from Microinverters
A solar inverter is a catch-all term for any inverter that works with solar panels. A microinverter is one type of solar inverter, but there are others.
Let’s take a look at different types of solar inverters:
String inverter: the most popular solar inverter for home use. Here, solar panels are connected like a string to the inverter. String inverters can be installed anywhere.
Hybrid inverter: lets you plug solar batteries like the Weize 100ah lithium LifePO4 into your solar panel setup. This is ideal if you want to add a battery to your system.
Battery inverter: battery inverters turn battery power into 230V alternating current. Instead of the grid, the current is sent to a switchboard.
Microinverter: microinverters are newer than string inverters and are more efficient. Let’s take a closer look at it.
What is a Microinverter?
Like other inverters, a microinverter turns DC into AC. Once converted, the current can be used to power electronics or transmitted into the grid.
The difference between a string inverter and a microinverter are:
- Microinverters are smaller, about the size of a book
- Each solar panel in your system will have one microinverter controlling it. In contrast, only one string inverter will manage your entire system.
String inverters and microinverters are both solar inverters, but microinverters work differently and are more efficient.
Microinverters vs. String Inverters
Microinverters are placed at the back of each solar panel, so if you have 24 solar panels, there will be 24 microinverters. With a string inverter, all 24 solar panels are plugged into the one inverter.
This sounds like the less expensive option, and it is. String inverters cost less than microinverters, but microinverters provide better output.
Because each solar panel has its own microinverter, it is indepdent of the other panels. This is important as you will see.
Suppose you have several solar panels connected in a series onto a string inverter. All those panels share the same circuit and properties.
If the output of one panel drops, the other solar panels will follow. If you have 8 x 300W solar panels and one panel produces just 250 watts, all the other solar panels will drop to 250 watts as well.
With microinverters this is not going to happen. Since each solar panel has its own inverter, it is self-contained. Even if one solar panel drops to 250 watts, the rest will not be affected.
With a string inverter, if even just one panel is shaded by a tree, the entire system will experience a performance drop. With a microinverter, the drop is limited only to the affected solar panel.
It is not just in performance that microinverters offer an advantage. it also applies in case of mechanical failure.
If you are using a string inverter and one solar panel malfunctions, it might affect the other solar panels. In a worst case scenario, you could end up without any solar power until you replace the damaged one.
If you have microinverters, the faulty solar panel won’t affect the others. Even if its output drops to zero it will not hamper the rest of the panels.
This applies to the microinverters too. If one of the inverters malfunctions, the rest of the system will continue to run.
If a string inverter goes down, the system cannot function. Your solar panels will continue to produce energy but without an inverter, it cannot be used by appliances.
Microinverters are mounted onto each solar panel and plugged in. Each one plugs into the next and its wiring is the same type used by AC appliances.
One disadvantage however, is that microinverters have to be installed on the roof. Since they have to be mounted on the panels, you have to go up the roof to install each one.
But this is not a problem for grid tied solar panels as there are professional solar installers available. Companies that sell solar panels for home have solar installers who will configure the system for you.
Scalability and Upgrade
It is easier to expand a solar panel system with microinverters than a string trimmer. Here’s why.
Suppose you want to try solar panels, but you don’t want to go all in yet.
Because microinverters have a 1:1 ratio with solar panels, you can configure the system as large or as small as you want. You can test things out with one solar panel and one microinverter for instance.
It is easy to add more solar panels and microinverters because they are plug and play. There is no need to modify the previously installed parts.
Expanding is difficult with a string inverter because the panels have to provide the right voltage level. If the voltage is too low or too high, the inverter will not run.
Some string inverters can handle 7-10 solar panels. Others can support more but these have to be configured in separate strings.
Expanding is difficult because string inverters are designed to run a specific number of solar panels. If you add more solar panels, the inverter might not work.
Solar panels should be oriented south so they face the sun and produce the best results. Panels that face other directions will have a lower output.
If your solar panels use a string inverter, all of them have to face south. If just one panel is oriented east, its output is going to drop. Because of the way string inverters work, the west-facing solar panels’ output will go down too.
That will not happen with microinverters because each solar panel is self-contained. You or the installer can arrange the panels in different ways to suit your needs.
Safety and Security
All grid tied solar panel systems must meet the Rapid Shutdown specifications set by the NEC (National Electric Code).
Not all string inverters conform to the latest Rapid Shutdown requirements. If you have an older string inverter, you’ll need to install a Rapid Shutdown add-on. This means additional costs for your system.
Microinverters meet these requirements and you don’t have to install any additional components. No need to spend any money to add new hardware.
I am an advocate of solar power. Through portablesolarexpert.com I want to share with all of you what I have learned and cotinue to learn about renewable energy.