Bidirectional Inverter Technology Explained 2023

Most solar owners don’t know it, but bidirectional inverter technology is invaluable to making solar energy as reliable as traditional fossil fuels.

In the past decade, we have seen the fastest proliferation of solar adoptions worldwide across different sectors. The most notable one is the recognition of the role electricity consumers have in the fight against climate change.

However, most novice consumers don’t realize that renewable energy (RE) technologies alone cannot completely replace fossil fuels. For example, let’s say you decide to go full solar without relying on your local utility (off-grid). Even with all the advancements in solar technology available in the market today, your electricity would still be highly dependent on the amount of sunlight available in your area. Imagine having no electricity at night! What a nightmare!

That’s why leading green energy experts and developers designed solutions to address these fundamental problems of RE, such as the “battery plus bidirectional inverter” combo we see in modern solar energy systems.

Today, we will help you understand everything you need to know about bidirectional inverters and how they level up the playing field in the realm of solar generators.

What is Bidirectional Inverter Technology?

To answer this question, let’s start by understanding what an inverter does. An inverter is a device that converts direct current (DC) power from various sources, such as DC batteries and solar panels, into alternating current (AC), which is the form of electricity we use at home or the office.

Common inverters you see in e-commerce nowadays only work one way. On the other hand, bidirectional inverters operate in a manner that allows both AC-DC and DC-AC conversions.

Some of you may be rolling your eyes, thinking, “Pfffft. Big deal! And we should care about this because...?”

Which begs the question: is there any real worth in knowing how bidirectional inverters work?

(Spoiler alert: Yes, there is.)

How does a Bidirectional Inverter Improve Your Solar Energy System

Adding a bidirectional inverter to your solar power system makes it more efficient, provides a higher safety standard, and gives more flexibility for charging options (which comes in handy when sunlight is scarce).

But before we tackle those, let’s go through a typical solar plus storage setup to highlight the impact of bidirectional inverters. This time, let’s emphasize how the power is converted between DC and AC before it reaches your devices.

Typical Solar Energy System Setup

Normal solar energy systems usually have four major components:

  1. Solar Panels – Harvests solar power and produces DC power
  2. Battery – Receives, stores, and delivers DC power
  3. Charge Controller – Converts DC solar power to another form of DC power to match your battery's voltage and current requirements. The modified DC power is then injected into your battery.
  4. Inverters – A device connected to the battery which converts DC power to AC that is acceptable for household use.
A typical residential solar system

 A typical residential solar system

Consider the image above. In a typical residential solar setup, electric power flows only in one direction. The process is straightforward: DC Solar power is (1) harvested, (2) stored in the battery, and (3) converted into usable AC power via an inverter.

Solar Energy System with a Bidirectional Inverter

Now, what happens when we replace the inverter with a bidirectional inverter?

With a bidirectional inverter, you get extra options regarding where your power comes from. In the other figure, you can see that bidirectional inverters allow you to charge your battery from your AC outlet. More about this later.

bidirectional inverter

A bidirectional inverter delivers power from the utility during normal operations (solid line in the blue box) and charges your battery. When an outage occurs, a bidirectional inverter instantaneously switches to your backup battery to ensure continuous power for your devices (broken lines in the blue box).

Bidirectional inverters also act as instantaneous switches to shift your power sources during emergencies. As you can see in the figure below, you usually get your main source of electricity from the AC outlet. However, when an incident happens, such as a blackout or brownout, your bidirectional inverter immediately detects the event. It then draws DC power from the battery to convert it into AC.

That being said, a solar energy system using a bidirectional inverter would look like the image below.

solar energy system with a bidirectional inverter

The two operating modes of a solar energy system that has a bidirectional inverter. The black, solid arrows represent the flow of electricity. Broken lines are activated when the main power supplies (solar or utility) are lost.

Benefits of a Bidirectional Inverter

Now that you know how a bidirectional inverter improves your solar energy system let’s summarize the benefits. With a bidirectional inverter, you get: (1) an enhanced inverter, (2) an extra battery charger, and (3) a fast-acting switch all in one.

Enhanced Inverter

Modern bidirectional inverters are built on modern MOSFET switch technology, which does two things for you:

  1. Faster switching speeds (higher safety standard); and
  2. Lower switching losses (better efficiency)

Compared to a basic inverter, bidirectional inverters also provide clean sine-wave outputs converting DC to AC. This means your electricity is clean (no harmonics) and won’t cause trouble for your electronics.

Extra Battery Charging Option

A bidirectional inverter also allows you to charge your battery via an outlet, which means you can charge your battery using both DC solar and AC outlets. This gives you an alternative way to charge your battery on the road when solar power is scarce. This translates to less charging time and more charging flexibility.

Fast-Acting Switch

Bidirectional inverters also keep your electricity running if disaster strikes. During an outage, a bidirectional inverter will immediately switch your power source from the AC outlet to your battery.

This is the reason why bidirectional inverters are considered nowadays when it comes to Uninterruptible Power Supply (UPS) feature.

However, you should take this information with a grain of salt. Bidirectional inverters currently cannot replace the professional-grade UPS out there used for large businesses and organizations.

Still, bidirectional inverters can be used for home applications as long as the switching delay is tolerable.

Summary

Bottom line: a bidirectional inverter allows you to:

  1. Charge your battery via an AC outlet on top of your solar charge controller;
  2. Immediately switch power sources from the outlet to your battery during outages (NOTE: around 100 milliseconds to half a second switching time compared to 10-millisecond switching of professional-grade UPS);
  3. It provides you with clean and efficient AC power thanks to its innate design. This means more protection for sensitive electronic devices;
  4. It can behave as a cheaper alternative to a UPS for general household applications;

Final Thoughts on Bidirectional Inverter

After all this, should you opt for a bidirectional inverter? It all depends on your situation and what you think has high worth.

For us, a bidirectional inverter is for green energy consumers who put a ton of value on high-quality electricity 24/7.

When shopping around for inverters, your main considerations should revolve around costs, power requirements, protection, and reliability.

There are intangibles, too, like post-purchase service, warranties, and product reviews.

For example, suppose you are a green energy consumer who uses a lot of sensitive electronics on the go. In that case, you should put a high price on portability, power reliability, stability, clean electricity, and peace of mind.

Therefore, making a DIY solar generator with a bidirectional inverter might suit your case. If you have the budget for it, look for modern solar generators with integrated bidirectional inverters that can act as a UPS during emergencies. This will save you space and puts all your needs in one device. No clunky baggage!