What is a solar inverter?

If solar panels are the brawn of your solar energy system, then the inverter is the brain. A solar inverter is basically a low-level computer—installed alongside the other components of your solar energy system—that “inverts” your energy from direct current (DC) to alternating current (AC).

What does a solar inverter do?

Think of your solar inverter as a translator and DC and AC as two different languages.

All the electrical wires running through your home carry or “speak” AC—as do your appliances and your utility grid. But your solar panels “speak” DC. So, in essence, there’s a communication barrier. Your solar energy system can’t send power to either your home or the utility grid without some help.

An inverter is what provides that help.

The main purpose of the solar inverter is to translate or “invert” the solar energy—generated by your solar panels—from DC to AC so that your home and utility grid can use it. So that’s the first and most crucial service it provides. But, in addition to inverting energy from one form to another, your inverter serves another important purpose: online communication.

Solar inverters allow you to connect your solar energy system to the internet, which in turn allows you to access information about your system (in our case, Vivint Solar homeowners can log in to their personal Account Center or the Vivint Solar app for Apple or Android at any time to see the amount of solar energy their system is producing). This is especially helpful when you want to compare your solar energy production against your household energy consumption (the energy reflected on your utility bill) or to ensure that your system is functioning properly.

Types of solar inverters

There are a handful of different inverter manufacturers out there but most companies focus on one of the inverter types laid out below. We’ve put them in order starting with types that include the fewest features to types with the most features.

The inverter you get will be based on a number of factors like: which company you hire, how much shade your home has, how you intend to use your solar inverter, and/or the utility requirements for residential solar in your area.

Straight String Inverter

For many years, a string inverter was the only option available. One of the main reasons for this was due to its lower overall upfront costs and limited long term maintenance requirements (since there is only one point of failure).

As an example of how a string inverter works, envision a swimmer is stuck in an ocean rip tide so bystanders on the beach form a human chain to rescue him from drowning (like the Panama City Beach rescue in July 2017). Each person in the chain represents a solar panel, and if one of them is weak or injured then it directly impacts the performance of the rest of the chain.

That is how a string inverter operates. Solar panels are connected in series, and if one of the panels in that series is shaded or gets dirty, then it impacts the performance of the rest of the string because the string can only perform to the level of its least productive panel.

So, if you have a house with multiple roof planes, or many surrounding trees, a straight string inverter may not be the optimal choice for you. However, if you live somewhere that is usually sunny and your house has a south facing roof, then a straight string inverter may be a great option for you because you’ll reap the maintenance benefits that come with simplicity and it will help you keep a little coin in your pocket.

Optimized String Inverter

The optimized string inverter is similar to the standard string inverter, except that it has power optimizers mounted underneath each solar panel on the roof. The power optimizer turns the solar panel into a “smart panel” and maximizes performance by monitoring and then communicating the performance of each solar panel individually. This allows you to get the most power out of your system.

Optimized string inverters will usually outperform a straight string system.

When it comes to providing a solution with power optimizers, one company dominates the residential market: SolarEdge. SolarEdge’s power optimized solution has been growing steadily for the past five+ years and as of December 2019 accounted for approximately 60% of all residential solar installs in the US.

Microinverter

Instead of having one larger inverter on the side of the house, a microinverter is mounted underneath every solar panel on the roof (similar to the way power optimizers are installed). Giving each panel its own microinverter allows greater flexibility with designs (technically, a person could install a system with one microinverter, and then add on later as needs arise). Also, the microinverter converts DC to AC right on the roof, whereas the optimizer transfers DC energy into the string inverter, which then converts DC to AC.

Enphase is the current standard-bearer in the microinverter arena. By year-end 2019, Enphase accounted for 19.2% of all residential solar installs in the United States.

Hybrid Inverter

Hybrid Inverters are the “New Kid on the Block” for inverter technology. A hybrid inverter is a combination of a PV (photovoltaic) inverter and a battery inverter and is available in straight string and optimized string options. This is becoming a popular choice for homeowners interested in energy backup options (even if the homeowner is not yet ready to install a battery) because it makes adding a battery much less expensive.

An additional feature (now offered by SolarEdge) is the ability to wire an Electric Vehicle (EV) charger to the inverter. This way, a homeowner would have the ability to add an EV charger when he/she is ready to go electric without the potential of incurring additional costs with a main panel upgrade.

So, as you can see, a hybrid inverter has all the features you need out of a PV inverter, but also offers enhancements to satisfy the most die-hard energy enthusiasts.

How do I decide what solar inverter is right for my home?

Hopefully by now it’s clear that inverters are a crucial aspect of a PV home energy system. So it’s important that you get the right inverter for your specific home energy needs and goals. There are a ton of different inverter manufacturers out there, and most companies carry more than one model of the inverter they supply. Here are some important things to keep in mind:

Independent solar vs. company solar

Most companies understand the solar requirements in each area and will choose an inverter for you based on your specific needs. Vivint Solar partners with multiple leading inverter manufacturers to be able to provide homeowners the optimal inverter for their specific situation. How, where, and when we use a specific inverter is based on extensive experience with the reasons explained above. Through a free consultation and custom system design, we understand the set up of the solar energy system for your roof, how you intend to use your energy production, and the regulations of residential solar in your area, so we can install the inverter that makes the most sense for you.

If you choose to go solar on your own instead of going through a solar company, you’ll want to do a lot of research about which type of inverter you should use, and whether it’s compatible with the rest of your system, and the regulations in your area (mentioned below). It’s a critical component of an efficient home energy system so you’ll want to be confident you’re picking the right one.

Regulations in your area

Some areas have specific regulations when it comes to residential solar. For example, in Massachusetts, local legislation has set a cap on the size of a solar energy system to qualify for net metering. That cap on system size is based on the maximum power output of the inverter (not the panels), because that sets the maximum amount of energy your system can send back to the grid at any one time. Because of this, it is possible to have your combined solar panel size under 10 kW but have a more powerful inverter that would unnecessarily push you over 10 kW. This is why—if you choose to set up a solar energy system on your own—it’s essential that you understand all the interconnection and legislative requirements in your area regarding net metering and applicable incentive programs.

How much does a solar inverter cost?

Similar to rooftop solar panels, inverters don’t fall into a “one size fits all” category when it comes to pricing. Inverters are so fundamental to a solar energy system that a lot of solar companies (including Vivint Solar) include the cost of the inverter in the overall price of a solar energy system, which can make it tricky to pinpoint the specific price of an inverter. You can find standalone inverters to purchase online but prices range wildly (anywhere between $1,500 and $20,000) because there are a lot of cost factors, which may include things like:

• Where you purchase the inverter: depending on where you purchase your inverter, the cost amount will likely fluctuate due to things like taxes, shipping, availability, etc. Because a lot of solar companies include the cost of the inverter in the total cost of the system, your purchasing options will be limited to third-party retailers who supply solar equipment to those in the market to install the solar energy system on their own.
• The size of your solar energy system: generally speaking, the larger the solar system you have, the higher functioning your solar inverter will need to be and thus the more costly. The biggest thing to keep in mind is that you'll want something that lasts, so be selective about cost, but not so selective that you compromise on quality.
• The type of solar agreement you’ve selected: your solar agreement will dictate how you choose to pay for your solar power and is based on the agreement options in your area. If you choose to sign up with a company like Vivint Solar, the cost of the equipment will likely be included in the overall cost of the system. Otherwise, you’ll likely purchase the inverter through a third-party and account for cost with the other solar equipment.
• Any special features specific to your area: some inverters come with built-in special features, such as revenue grade meters (which are sometimes required by state incentive programs and are more accurate regarding energy production), secure power supplies (like the SMA Sunnyboy) and smart inverter settings/functionality (which are required in select jurisdictions).

To get a better idea of the cost options available to homeowners with a Vivint Solar system, check out the different solar plans we offer and how they work.

Now what?

If you’re interested in taking control of your home energy, schedule a simple (and free) consultation with one of our solar representatives. We’ll go through your options and explain the benefits that can come from using energy from the sun to power your home.