Solar Inverters: Understanding the Basics

Getting a solar system is about more than getting just renewable and green energy. It provides you with a way to reduce your yearly energy bill. The systems have a high initial price, but the products and equipment last many years and will save you time and money in the long run. 

Water and wind are also options for residential and industrial green energy, but they are often more expensive. They may not be as portable as solar panels also, as they are often bigger. So, if you are traveling or want to be off-grid, then solar panels are a great option. 

One major part of solar system technology is the inverter. Using a microinverter or grid-tie inverter can allow you to use both the utility grid and go off-grid for emergency power when you need to.

These power systems have higher costs than normal solar power, due to extra wiring, monitoring, consumption, and an extra unit or several, but this allows you to use your power, and run electronics, even when the power grid is down.

How Do Solar Inverters Work?

The purpose of a solar inverter is to take the electricity coming in from the solar panels and convert it into electricity that your home and home appliances can use. The power that solar panels create runs in direct current, or DC power. The power that most homes run on is alternating current, or AC power. 

In a home, an inverter can serve many different purposes. They can convert solar energy into AC power using transistors to change the direction the voltage runs. This is their most common use, but they have other purposes as well. They can be used to monitor the system as well. 

An inverter can also monitor the system and communicate with apps on WiFi or Bluetooth to alert the user when something is wrong. Additionally, they allow solar systems to run on their own without going back to the grid. 

Most of the time, for homes, you can save money by not getting an inverter or battery. The grid will take your power, convert it for you, and send it back to your home. Then they will take the extra you aren’t using and buy it back from you. 

However, if you want to be more off-grid, you can buy solar inverters and a battery system. The inverter allows you to take your solar energy and use it directly in your home. You can also store energy in the batteries and pull it out whenever you need it, such as at night. 

It is important to note that solar inverters cap your power amount. No matter the size of your batteries or your solar panels, you can only get as much AC power as your inverter can produce at once. Usually, you can get them in 1000-watt increments, such as a 1000, 2000, or 3000-watt inverter. 

The Advantages

When you look online, most of the benefits and drawbacks compare the solar system as a whole, and not the benefits of getting a battery backup and inverter for your solar system, versus just sending it back to the grid. However, there are distinct benefits to getting a battery backup and an inverter. 

For example, it allows you to be a little less dependent on the grid. Even if you stay hooked up to the grid and just get a battery backup, you can mostly run from the grid and get discounts on your utility bill, but if the grid shuts down, you can run on your batteries and inverter. 

Some inverters can also produce a more pure sine wave. This allows for more efficiency, which means you have the potential to get more power out of your system. 

While batteries and inverters are expensive, they are still considered less costly than a generator. They also don’t release emissions, unlike gas generators. They can also start up immediately after the grid goes down. You don’t need to go outside and start the generator.

That way, if you aren’t home, you don’t have to worry about the stuff in your fridge going bad. The inverter is also multifunctional, converting power, and keeping an eye on your system.

This means that it can watch your system and alert you when something is wrong. They can also help you keep track of your battery chargers, connections, power output, and more, no matter the complexity. 

For example, if you are getting full sun, but not a lot of power going in, the inverter can show you that, and it might be a warning that something is wrong with your system. You can also watch the load and input via an app so you know if any issues are present with the panels. 

MPPT chargers also track loads and solar ranges for most applications, but they focus on different parts, so it is beneficial to have both, so you can keep track of every number and know when something is wrong or when you aren’t at your top range. 

It also alerts you to electrical faults or arcs. The inverter will not only tell you that something is wrong, but it will also shut down to prevent any further damage to your electrical system. 

The Disadvantages

Solar inverters have a lot more mechanical parts than anything else in the system. This means that they are usually the most common thing to break. Since they are already expensive to purchase, it can be frustrating when one breaks. 

Additionally, inverters can be pretty big. This means that you have to make space for them, and the battery banks you want in your home. For smaller places with little storage, it may not be easy to find a place that gets enough air circulation and is a good temperature for these devices. 

That is another downside. If you are using the inverter so that your house can be independent of the grid, or at least work when the power goes out, you need a battery bank. If you get good batteries, they can easily be around $3,000 each! 

Considering you usually want at least two, you can easily put as much money into the inverter and battery as you did for the rest of the system. This means you are investing a huge amount of money to just install an emergency backup. 

Inverter Types

String Inverters

A string inverter is also known as a central inverter. It works well for simple solar systems. It is usually the cheapest, as one inverter runs several different panels. Usually, these string inverters are located in places like the basement or garage. 

Since they are so simple, they are more durable. However, if one solar panel isn’t working at its maximum potential, it will affect the whole system. This means that even if just one panel is in the shade, the whole system is getting a lower performance. 

Additionally, if solar panels can’t be all linked up via strings, then the system is too complex for a string inverter to work. 

But these work well for a simple system on a house with plenty of roof space and a lot of direct sun. 

Micro Inverters

Where string inverters are central, microinverters are distributed inverters. Instead of using one inverter for your whole system, you need one next to each solar panel. These inverters transform the power from that one solar panel and turn it into AC power right at the panel. 

This means you can see how each panel is working individually and determine exactly where the problem is. 

This is a good option for systems with a lot of complexity, or where panel devices are different sizes and are getting different sunlight based on the site they are in. They also work if you are thinking about increasing your system size, as it is easy to expand. 

However, they are a lot more expensive than string inverters. They are also located on the roof or next to the solar panels, so maintenance can be difficult. They produce the maximum output, even on a more complicated roof, where solar panels can’t all face the same direction or get the most amount of light. 

Hybrid Inverters

Hybrid inverters are relatively new inventions. They combine a battery and a PV inverter. They allow you to get it in a central or distributed version.

It can convert DC to AC, but also AC to DC so you can still charge electric vehicles and solar batteries. It is a good choice for those that have Electric Vehicles (EVs) as it allows you to easily charge them. 

Off-Grid Inverters

Off-grid inverters are designed to allow people to get off-grid. They are similar to grid-tie inverters like the three above but have a few differences. The main one is that these inverters aren’t designed to send power to and from the grid. 

They still convert solar energy into AC power that your home uses, but don’t work with the grid at all. You also need more parts for off-grid solar panels. For example, getting batteries and charge controllers are a must for energy generation even at night.

You will also need a lot more circuit breakers. This makes the system as a whole much more expensive just in parts. However, it also is more difficult to install due to the number of wires and parts, so the installation cost is higher. 

Sizing an Off-Grid Solar Inverter

When you are sizing an inverter, it is very important you get the right size. You need to make sure you can power all of your basic appliances like microwaves, washers, dryers, and fridges.

You also want to try and avoid getting one that is too large as well, though. The larger they are, the more energy is lost and wasted. 

We recommend figuring out your basic energy requirements, and then going up at least one size more. This allows for a little extra growth, or if you are going to need more appliances some days. 

Though it is complicated, it is well worth going through what you normally use in a day, and how much power it all draws. Most appliances will tell you how much power they draw at peak, and many devices and lights you can find online. 

For the whole system, you need to determine the number of hours that you get sunlight, and how much power you use in a day so you can decide how big your batteries should be. 

However, for the inverter, you just need to determine how much power you will use at once. The inverter just determines how much AC power is produced at a time.

For example, 2000-watt inverters are only capable of handling just about 2000 watts of constant power, so if you need more than this at one time, it is worth looking at bigger inverters.

Off-grid Inverters	Off-grid Inverters
Under 1 kilowatt	Small home, not used constantly. Can power small appliances like a TV, lights, and phones, but not heavy appliances
1-2 kilowatts	It can power a fridge, lights, and small devices like phones and TVs
2-4 kilowatts	Small, but highly efficient homes, RVs
4-8 kilowatts	Most sensible off-grid homes. It can power big appliances, wells, and pumps
8-16 kilowatts	Larger homes like ranches, farms, and commercial buildings
Above 16 kilowatts	Very large homes, multi-family homes, and commercial buildings

Sizing a Grid-Tie Solar Inverter

Sizing a grid-tie solar inverter is similar to an off-grid one. However, you can make some mistakes without a problem, and you don’t have to worry about the peak power of your devices.

If you want to mostly rely solely on your inverter, you can go through and calculate the total amount you need. 

However, if you just want to cover most of it, you can do that as well. Whatever your inverter can’t provide will be given to you by the grid. So it is just how much you want your system to produce for you, or how much power you want to be able to use in an emergency. 

Most people say that you want your inverter to be around 85% of the total power of the solar array to get the most out of your energy production. 

Installation of a Solar Inverter

Most of the time, a solar inverter should be installed by a professional, or at least with support on speed dial in case there is a problem during your setup. This allows you to make sure all of your wires and cables are correct.

It also makes sure they go to the best place for them, and that you don’t get anything mixed up. Remember, microinverters and string inverters go in different parts of your solar system. 

They are usually heavy, especially string inverters, so remember that putting them up somewhere high can be difficult. You also want to think about which side takes in the DC power and which side lets out the AC from the inverter.

Putting them upside down can make cable installation messy and tricky. Always make sure that your inverter is in a place where temperatures are moderate and constant, and where it will get plenty of airflow. 

Maintenance on a Solar Inverter

Try to keep your inverter somewhere it won’t get a lot of dust. Dust can severely mess up your system and make it struggle to run, eventually wearing down the motor. 

Your inverter should also stay fairly cool. Too hot or humid, and your inverter will wear out much faster. 

Try not to always run your inverter at max. If you are constantly right at the edge of the amount your inverter can produce, it may be worth scaling back your appliances or getting a bigger inverter. 

Make sure you take the time to clean it every few months. You can wipe it down on the outside yourself every few days to get rid of any oil and dust. However, for internal cleaning, you should look at hiring a professional. 

Finally, you should hire a professional to look over your inverter at least yearly. They can help make sure everything is running properly and perform any small repairs that might be needed. 

Choosing an Inverter

Inverter Rating Criteria

Inverters are rated based on their volt-ampere (VA) rating. VA is the voltage and current that is supplied to the home and appliances. To calculate this, you look at the amount of power that your home needs at once, and then divide it by the power factor.

Most inverters run on a power factor of 0.7 to 0.8, so if you don’t know the exact amount, you can guess. Using this and the wattage requirements of your home will tell you how strong your inverter needs to be. 

Application for Inverters

Do you need an inverter to go off-grid, or a simple string inverter that works with all your panels at once? Perhaps you want a hybrid so you can charge your EV?

If you live in an area where you get a lot of shading, look at getting microinverters as they can make sure your panels have better optimizers. Figuring out what you want, and how much money you have is important to figuring out the kind of inverter you need. 

Also, look at reviews and the efficiency of solar inverters. There are some industry standards, but every type and every standard throughout the world is different. 

Look for Regulations on Inverters

Some local governments have regulations on inverters. Sometimes, they regulate what kind or size the inverter can be. However, much more often, they have regulations on how far away inverters can be from the meter box, and the distance between the inverter and other devices. 

This can be important to determine which panels you can use. For example, if your solar panels are too far from your meter box, you may not be able to use microinverters, and have to use a string or a hybrid to get closer to the meter box. 

FAQ

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