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Sunlight Backup: Exact Solar’s IQ8 Microinverter Case Study

Aerial drone shot of Lisa and Steve’s system

With Enphase’s IQ8 Microinverters, homeowners can keep critical power loads on during daytime power outages— without buying battery backup systems. It’s called “sunlight backup.” We installed this not-widely used technology on Steve and Lisa’s house, and it works like a charm.

When Steve and Lisa were shopping around for a solar company, IQ8 microinverters had just come out. Only a few other companies were willing to install this new technology, and other than Exact Solar, no one local would even try. 

They chose Exact Solar for three reasons:

  1. Steve knew he wanted someone thorough because he needed cutting-edge technology to be installed. 
  2. They’d heard horror stories about other solar companies’ customer service and wanted to ensure that they’d always be able to get a hold of someone. 
  3. They wanted to support a local business, and the other companies who bid to build their system were from out of state. 

In our follow-up interview with the Whites, Lisa explained: 

Before they even started shopping around for companies, Steve had decided he wanted Enphase’s new sunlight backup technology. Because the Whites have several chest freezers of food that will spoil if they experience a sustained power outage, and they didn’t want to buy a battery backup system, sunlight backup seemed like the right technology for their situation. 

So, How Does Sunlight Backup Work? 

Before we get into the nitty-gritty, it’s important to note that sunlight backup is not for everyone. If you live in an area with frequent, sustained power outages or are considering an off-grid array, you’re better off adding a battery bank to your solar system.

We reached out to Enphase when writing this article, and even they don’t recommend sunlight backup as a standalone. They recommend adding sunlight backup with a battery, which gives you two layers of protection against outages, not just one. 

A diagram from Enphase showing how battery backup helps keep your power on in an outage. Image used with permission.

Enphase recommends adding one of their IQ batteries so you can power your house through the night in the event of an outage. 

For most solar homeowners, when a power outage happens, electricity is shut off in their homes. If they don’t have battery backup, their power will go off like everyone else’s. 


It’s for the safety of line workers during power outages. If you own a grid-tied system, it’s always producing electricity, and back-feeding any extra electricity it produces into the electric grid. During an outage, this becomes incredibly dangerous.

Grid-tied solar systems are legally required to cut off during outages because if they’re back-feeding their extra power during an outage, power lines could be live while linemen are working on them. Even if there’s no power coming from the power plant, there’s power coming from your solar system, and it’s enough to kill or seriously injure someone.

You have two options if you want your solar system to keep your power on during an outage:

  1. Battery backup (this was the only option until a few years ago) 
  2. Sunlight backup

With sunlight backup, the instant the power goes out, Enphase’s IQ8 microinverters stop power from flowing back into the grid and start feeding it into critical loads in your house. 

When you and your installer design a sunlight backup system together, you choose critical loads in your house (Steve and Lisa designated 8) that your system will keep feeding power to during an outage. Think refrigerators, freezers, maybe your stove so you can heat up food, etc.

A sunlight backup system can handle eight 120V circuits or 4 240V circuits. 

The eight 120V circuits the Whites designated to run on sunlight backup

It’s important to note that sunlight backup only works when the sun is shining. If there are no batteries storing the power, the power doesn’t have anywhere to go! So sunlight backup is only a daytime solution. 

With the Enphase app, you can designate which loads the system will prioritize with the limited power that’s generated. If there’s a limited amount of electricity being generated by your solar system due to declining sunlight late in the day or massive cloud cover caused by a storm, the system will route the power to your highest-priority loads first.

Components of a Sunlight Backup System

A conventional grid-tied solar system is relatively simple. You have solar panels feeding electricity through microinverters, into a combiner box, that are wired into breakers in your fuse panel to power your house.

Any extra power that your system generates will be fed into the power grid. This diagram is a bit oversimplified, but it gives you a general idea of a basic home solar system.

Image of a grid-tied solar system from Enphase used with permission. 

There are a few more components in a sunlight backup system. 

Sunlight backup is considerably more complex because there need to be more fail-safes. It’s imperative that in the event of an outage, no power goes back to the grid.

 It’s also necessary to attach a lot more wiring to your home panel, to ensure that your sunlight backup system can power your designated circuits. 

Here are the components of a sunlight backup system:

An image from Enphase showing the components of a sunlight backup system (used with permission).

The pieces that make up a sunlight backup system are:

  • Solar panels: Photovoltaic panels on your roof provide continuous power, back-feeding the electrical grid through your two-way meter.
  • IQ8 Series Microinverters: Microinverters are attached behind your solar panels and feed power to the combiner box. These smart devices help your solar panels work with and without the power grid. They have a chip that instantly switches between on and off-grid power in an outage.
  • The Combiner: Combines all the wires from your solar panels into one output and includes the IQ Gateway. This gateway lets you check on your solar system from your phone or computer using the Enphase App.
  • The System Controller 2: A smart switch that automatically uses your solar panels to power your house when the electricity goes out. It can work with the IQ8 Microinverters, special batteries, and other backup power sources.
  • The Load Controller: Allows you to manage how much power goes to big appliances like your clothes dryer or car charger and smaller loads like lights and fans. You can have up to two of these controllers to handle more appliances, but you need at least one of these controllers for the sunlight backup system to work.
  • The System Shutdown Switch: A critical safety tool for the IQ8 backup system. If you ever need to turn off your solar power system (rare but legally necessary), this switch connects your house to the regular power grid and turns off the sunlight backup. 

Enphase has written a comprehensive guide on their website that gets into the nitty-gritty details of how sunlight backup works. If you’d like to dive deep into the details of how it works, click here

When we installed all of these components in Steve and Lisa’s house, here’s what it looked like:

When we reached out to Steve and Lisa to write this article, they gushed about Exact Solar being local and how great our customer service was. But at the very end of the interview, when we asked “Is there anything you would change about your experience?” Lisa said:

Sunlight backup is an interesting technology with a lot of potential, but it doesn’t make sense for everyone. If you’re considering a sunlight backup system, weigh your options carefully before committing.

Our team of solar experts are ready to help you along your solar journey! Contact us today for a free, no-hassle consultation.

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