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Choosing a Solar Battery Backup System for Your Home

Introduction: Why Use a Solar Battery Backup System?

In a grid-tie solar system, any excess energy your panels generate is sent back to the grid. Solar battery backup systems enable you to store that excess energy for future use, protecting your home in case of grid failure, extreme weather, or other service interruptions, saving money and giving you independence from your utility provider.

There are many misconceptions about how solar batteries are used for grid-tie systems versus off-grid systems. So first, let’s quickly review the difference between grid-tie and off-grid solar systems.

Grid-Tie Backup Systems vs. Off-Grid Solar: What’s the Difference?

Grid-tie systems connect you to the public utility grid -- the entity you pay your electric bills to. For example, if you've been paying an electric bill and then add solar panels to your home or business, you have a grid-tie system. Your solar panels feed electricity into the grid, and the utility credits your account for the power your panels generate.

Most people with access to power lines choose grid-tie systems for their dependability. However, basic grid-tie systems are vulnerable to power outages caused by natural disasters, storms, and equipment failures. When you’re connected to the grid, your electricity is disabled as a safety measure when the grid power fails -- even if you have solar panels.

These vulnerabilities are solved by a grid-tie system with battery backup, also known as an energy storage system.

Like a grid-tie system without battery backup, your grid-tie battery backup system will still reduce your electric bill and allow your home to run on clean solar power. But when the grid goes down, your system's battery bank kicks in to provide power for your home. Even when the grid is working there are benefits: a solar battery can offset your energy costs when electricity rates are at their highest. Peak times are usually after sundown, but your utility’s rate structure may differ.

Off-grid systems are entirely independent of the grid. While this may sound desirable to some people, it’s not without its drawbacks. Off-grid systems cost more than grid-tied systems but may be necessary for remote locations. In addition, off-grid systems make you 100% responsible for your power needs, requiring batteries and a generator to provide backup power in emergencies (and at night!).

Grid-Tie Solar Battery Backup Systems

Off-Grid Solar Battery Systems

Popular for properties with access to the grid Best for properties without access to power lines
Must be added on to a basic grid-tie system at an additional cost, but provides power for critical needs when necessary The only solar option when there are power needs and there is no access to the grid
Uses a dual-function inverter to send excess energy to the grid and utilize stored battery power when needed Uses a stand-alone inverter to convert DC power to AC for direct home usage

What is the Difference Between Grid Tie and Off Grid Solar?

Find out more information about the difference between grid tie and off grid solar and which one is right for you.

How Energy Storage Systems Work

During sunlight hours, your solar panels are producing energy which either powers your home or is stored in your batteries.

This stored energy can be used to:

  • Power your home at least partially during power outages and emergencies
  • Power your home during peak demand times, saving utility costs

If your batteries are fully charged and your panels still produce energy, your system will send that energy to the grid, generating utility credits through the Net Metering program.

How does a solar battery work?

  1. When the sun’s up, the solar system charges the battery.
  2. Excess solar power is stored in the battery, instead of the grid.
  3. When the sun goes down, the battery powers your home.

Can You Add a Backup Battery to an Existing Solar System?

The ability to add a battery backup system depends on whether your solar panel system was designed to accommodate adding energy storage.

A "storage-ready" system has an inverter that can integrate a battery into your solar system setup. Batteries are easy to install in a storage-ready system and don’t require much additional equipment. However, if your solar panel system was not designed to add extra storage, the installation will be more complicated. In that case, it will require either an AC coupled or DC coupled solution.

AC coupled solution DC coupled/inverter

Integrates into existing systems

Keeps your system’s current inverter but integrates an additional inverter into your energy system.

Replaces system

A DC coupled inverter replaces your existing inverter with one that’s battery-compatible.

Saves money upfront

AC coupled solutions work with your existing system.

Costly upfront

Switching to DC sometimes requires redesign and rewiring to incorporate it.

Less efficient than single inverters

AC coupled systems result in small efficiency losses over time.

More efficient

DC coupled solutions are more efficient, as there is less energy loss in converting DC to AC energy to power your system.

AC/DC coupled solutions

Types of Solar Batteries

Solar battery backup systems use deep cycle batteries. Deep cycle batteries resemble car batteries but are designed specifically for powering electrical appliances for long periods.

Lithium ion (the most popular) and sealed lead acid batteries are the most common deep cycle batteries used for solar battery backup systems. Here’s the difference between them:

Sealed Lead Acid Batteries

Sealed lead acid batteries are a less expensive option.

There are two sealed lead acid battery types: gel and absorbent glass mat (AGM) batteries.

  • AGM batteries are cheaper and have a better temperature range than gel batteries.
  • Gel batteries tend to have lower charge and output rates than AGM batteries and take longer to recharge but do last longer.

Lead acid batteries can overheat if charged too quickly, limiting how much charge current they can handle.

Lithium Ion Batteries

Lithium ion batteries are a more expensive option. However, they last four times longer than lead acid batteries, have high discharge and recharge rates, weigh less and are maintenance-free.

What to Consider When Choosing Solar Battery Backups

There are four factors to consider when choosing your solar battery backup system: price, battery storage capacity, cycle life, and voltage.

1. Price

Batteries range from $100 for the cheapest lead acid battery to $1,500+ for a lithium iron battery. Remember to look beyond the upfront costs and consider maintenance and replacement schedules as well. While lithium ion batteries cost more, they do outlive lead acid batteries and take care of themselves.

2. Battery Storage Capacity

Solar battery capacity measures the amount of energy you can store, measured in total kilowatt hours. If you need to power necessary appliances for long periods, you'll need batteries that can handle larger loads.

In addition, you can choose between whole home and partial home backups. Partial home backups (to power specific rooms or appliances) are generally favored as they require less battery storage capacity. However, whole home backups are possible with the correct system configuration.

3. Cycle Life

Cycle life indicates the number of charge and discharge cycles a battery can provide before the capacity drops. Battery technology types differ, so it’s essential to compare the capacity of each.

4. Voltage

You must check the battery bank's voltage to ensure it is compatible with your solar system before purchasing. Choosing a higher voltage battery bank can help reduce system costs, and may be necessary for larger applications.

Benefits of Having a Solar Battery Backup for Your Home

Why choose a solar battery backup system?

  • Stored energy is pulled from your batteries rather than the grid, saving money.
  • Stored energy maintains power supply to essential appliances during outages, giving you peace of mind.
  • Excess stored energy is still sent back to the grid for utility credits.
  • Backup batteries are beneficial in areas that experience unpredictable weather and long-lasting outages.
  • Stored energy reduces your home’s carbon footprint.

Enphase Enlighten - Designed To Be Completely Worry-Free

At the core of every Ensemble storage technology product, you’ll find an unparalleled set of features, designed with your needs in mind.

Load control

Load control

Turn power-hungry appliances on and off automatically or manually from the Enphase app to conserve your battery life when running on backup power.

Easy to monitor

Easy to monitor

Transfer to grid power when your battery is fully charged. Enphase Storage updates itself automatically to deliver the latest software features.

  • One platform for commissioning, monitoring, and troubleshooting for solar and storage
  • Whole or partial home backup with service up to 200A
Start small and go big

Start small and go big

Designed to be flexible.

  • Compatible with IQ 6 and IQ 7 series microinverters
  • Mix and match 3.4kWh and 10.1kWh storage systems
  • Smart plug-n-play distributed architecture makes installation quick and easy
  • All-in-one commissioning simplifies and accelerates setup time
Low voltage. High safety.

Low voltage. High safety.

Enphase Storage operates with low-voltage DC power, avoiding the dangers that come with high-voltage DC power.

  • No high-voltage DC batteries
  • Lithium iron phosphate (LFP) battery chemistry
  • End-to-end AC-coupled system architecture

Enphase Ensemble Components

Encharge 10 storage system

Encharge 10 storage system

The Encharge 10 all-in-one AC-coupled storage system, comprised of three base Encharge 3 storage units, provides a total usable energy capacity of 10.1kWh and twelve embedded grid-forming microinverters. Connect multiple Encharge 10 storage systems to maximize backup potential for whole home backup.

Encharge 3 storage system

Encharge 3 storage system

The Encharge 3 all-in-one AC-coupled storage system provides a total usable energy capacity of 3.4kWh and four embedded grid-forming microinverters. It provides great flexibility in starting small and adding incremental capacity.

Enpower smart switch

Enpower smart switch

The Enpower smart switch connects the home to grid power, the Encharge storage system and PV. It provides microgrid interconnection device (MID) functionality by automatically detecting and seamlessly transitioning the system from grid power to backup power in the event of a grid failure.

Wireless communication kit

Wireless communication kit

The wireless communication kit enables direct communication between Encharge, Enpower, and IQ Envoy. It uses 2.4 GHz and 915 MHz frequencies in parallel for maximum reliability. The kit will be connected to one of the USB ports on the IQ Envoy.

IQ combiner

IQ combiner

The IQ combiner consolidates interconnection equipment into a single enclosure and streamlines PV and storage installations by providing a consistent, pre-wired solution for residential applications. Install the new communication kit in any IQ combiner to enable wireless communication with Encharge and Enpower. Installation of the cellular modem is required unless already present in the IQ combiner. This ensures the best performance of your system.

iq-series-microinverters for Ensemble technology

IQ series microinverters for Ensemble technology

Ensemble technology for battery backup configurations is fully compatible with IQ 7™ and IQ 6 series microinverters, making retrofit upgrades as simple as new installations.

Solar Battery Backup Installation

Whether you want to include a backup battery in a new solar panel system or add energy storage to an existing system, there are a few things you should know. Here are a few tips to get you started on the right path.

  • Check on battery rebate programs for state and federal tax credits and rebates.
  • Share your electricity usage and storage objectives to determine which system is the right fit for your home if you’re working with an installer.
  • Contact your utility and confirm that every component in your energy storage system spec has been approved for interconnection before you start. Some jurisdictions require re-permitting existing solar systems and wiring upgrades if you install a new inverter.

If you need help with a solar battery backup solution, just reach out to the experts at GoGreenSolar. We have you covered, whether you’re retrofitting an existing solar panel system with battery backup, or just starting out with solar panels.

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