How to Select a Solar System with Battery Backup

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“Harnessing the sun’s potential as usable energy for your home”

As climate change is making extreme weather a more frequent occurrence, homeowners are seeking ways to keep the lights on when the grid goes down. Particularly in the West, where we have wildfire-induced brownouts, rolling blackouts, and Public Safety Power Shutoffs, the potential for outages has never been greater. No longer satisfied or confident with traditional, fossil-based portable generators, many consumers are considering solar for disaster preparedness.

With declining costs (installation costs have fallen some 70% in the past decade) and rapidly advancing technologies, now is a brilliant time to consider a PV system with battery backup. Solar is a clean, renewable energy source, beneficial for the environment. A solar system will save you money now and, in the future, reduce your carbon footprint and dependence on public utilities, and protect your home, powering appliances, and your electronics until power is restored after an outage.

As interest and demand continue to increase (millions of Americans already use solar, and more than half of all homeowners are at least considering an installation), we thought this an ideal time to address your most pressing questions related to solar and battery backup.

Considerations in Going Solar

As we progress through this article, we first explain a solar system with battery backup, then address essential considerations in your decision to go green. We eliminate the technical jargon as best possible and use laymen’s terms to make the discussion more palatable.

  • Selecting a reputable, experienced installer
  • Your objectives and priorities
  • System sizing and design
  • Financing your system – ownership or lease, cash, or solar loan

Your Solar System

Your solar system starts with a single photovoltaic module made of semiconductor material, known as a cell. These cells are sealed in environmentally protective materials and form the building blocks of PV panels. Panels are then connected to create the array you see on your neighbor’s rooftop. The array connects to the electrical grid as an integral part of your solar system.

The next essential component of your system is the solar inverter which converts the variable direct current (DC) output of your PV panel into a usable frequency alternating current (AC) – your electronics and appliances operate on AC. Although all inverters have the same basic function, there are different types of inverters with new technological breakthroughs.

Finally, the AC electricity from your inverter flows to a main electric service panel, commonly known as the breaker box or load center.  The service panel receives the incoming electricity and distributes it to each of the circuits that supply your various lights, outlets, appliances, and other devices – or sends excess energy back to the utility grid if your system produces more energy than you consume.

Solar with Battery Backup Explained

According to Elon Musk, the sun’s incredible energy is sufficient to power all of civilization. The challenge is harnessing this awesome potential into storable and usable energy – batteries will be an essential piece of the solution.

From a residential perspective, most solar systems simply do not supply adequate power consistently. Batteries, however, can store the energy generated by your PV system, allowing you to use that electricity around the clock – not just when the sun is out, expanding your system’s effectiveness. With batteries, more of your home’s overall electricity use is generated by your array, and you can avoid using the grid during peak periods, further reducing your utility bill. Perhaps most importantly, a battery system provides backup during power outages for basic safety, comfort, and communication.

In an off-grid situation, batteries are a necessity, whereas, in a grid-tied system, batteries are not mandatory – should you produce more electricity than you consume, the excess capacity is put back onto the utility grid through net metering. If, however, your objective is to minimize or eliminate your utility energy costs, a battery backup system can be installed to offset grid usage, especially during the most expensive on-peak utility hours. Plus, a grid-tied solar battery system provides the disaster preparedness you seek with extra protection against grid blackouts.

Types of Solar Batteries

Batteries for solar storage are not new. Lead-acid batteries, FLA (flooded lead-acid), and SLA (sealed lead-acid) are time-tested technologies that have been used in off-grid applications for decades. This article focuses on the more technologically advanced lithium-ion batteries used in residential, grid-tied systems. Lithium-ion batteries are rechargeable batteries that use lithium as one of their active components.

Lithium-ion and Lithium-Iron Phosphate (LFP) batteries, such as those used in laptops and cellphones, have been engineered to be safe, durable, lighter, and more compact and are now the battery of choice in the residential solar energy space. (The Lithium-Iron Phosphate battery is a lithium-ion battery known for its long life and safety.) Although more expensive, the benefits of lithium-ion, virtually no maintenance, more efficient power usage, and more usable storage capacity justify the higher cost.

Perhaps the best-known residential solar battery is the Tesla Powerwall – introduced in 2015; the Powerwall is now in its third iteration. However, when selecting a battery for your system, you have options including:

  • Enphase -Ensemble
  • Generac – Pika
  • LG Chem Primary Lithium-ion Battery
  • Shell Oil – Sonnen eco
  • Fortress – eVault, Lithium-Iron Phosphate
  • Panasonic EverVolt
  • SunPower SunVault

fortress power batteryIf you install a completely new solar system, you have a wide range of options in your solar equipment, panels, batteries, and type inverter. Although many new installations use DC-coupled batteries, meaning the DC electricity produced by your panels feeds directly into your home to a central inverter, the safer, more efficient alternative is module-level power electronics (MLPEs) such as the power optimizer or microinverter. Microinverters attach to each individual solar panel (module-level) – so that the DC energy is converted to AC at each panel on your roof so that high-voltage DC need not enter your home.

Adding batteries to an existing solar system, once a problematic proposition, can now be accomplished with hybrid inverters. Hybrids take energy input as either AC or DC, determine where power is needed, and their software makes the necessary conversion. They can charge batteries with direct current (DC) or use alternating current (AC) to power the home or feed back to the grid. Hybrid inverters are useful in retrofitting battery systems as they are compatible with different brands of batteries.

Hybrid inverters also generate a “grid signal,” designed to let your existing solar system keep running in an outage, powering your home, charging the battery by day, and using the battery to power your home at night.

Whether installing a new system or adding battery storage to an existing array, it’s important to do your due diligence when selecting an installer. Your installer is responsible for analyzing your energy needs and sizing your system, system design, licenses and permits, equipment, maintenance and repairs, installation, and warranties.

Industry experts recommend you interview several installers. Each will handle only a limited selection of the available solar panel and battery brands.

Attributes of an Experienced and Reputable Installer

Key considerations when developing your shortlist of installers to be interviewed:

  • Experience in the industry
  • Local knowledge and expertise
  • Services offered – custom installation capabilities
  • Selection of products and materials
  • Solar financing options
  • Credentials – We recommend that you only consider providers who have certification from the North American Board of Certified Energy Practitioners (NABCEP)
  • Customer Reviews

Terms and Specs When Selecting a Battery Backup

When discussing batteries with your installer, understand that not all lithium-ion batteries are the same. You will come across a number of complicated product specifications. The most critical items for consideration are the battery type, capacity and power ratings, depth of discharge (DoD), efficiency, and warranty during your evaluation.

Capacity relates to the total energy a battery can store and provide for your energy needs, measured in kilowatt-hours (kWh). Capacity is a function of voltage, amp-hours, and rate of discharge.

Power rating – capacity tells you how much energy a battery can store but doesn’t tell you how much electricity a battery can deliver at a given moment. A power rating is the amount of electricity that a battery can deliver at one time, measured in kilowatts (kW).

Voltage is a unit of measure for batteries. Multiple batteries may be used together to achieve the proper voltage.

Every time a battery discharges and is recharged, it’s one cycle. Estimating the life of a battery is not based on the warranty in terms of time. Instead, it’s calculated by the number of times a battery can charge and discharge (cycle) throughout its lifespan.

Depth of Discharge of a battery refers to the amount of a battery’s capacity used.

Round Trip Efficiency – batteries are not 100% efficient as power is lost in the charge and discharge process. A battery’s efficiency represents the amount of energy that can be used as a percentage of energy stored. Most lithium batteries are about 95-98% efficient.

And, of course, the warranty. Most lithium-ion batteries from best-in-class manufacturers are for ten years. So your solar array, with its twenty-five-year lifespan, will outlast your batteries.

Your Objectives and Priorities

Your installer will help determine how solar will work best on your home and advise how it will help you achieve your goals. Defining your objectives and priorities is an essential first step when deliberating going solar. For example, are your priorities primarily financial, reducing or eliminating your energy expenditures now and in the future, maximizing your return on investment, or increasing your home’s resale value? Are aesthetics an important consideration? Environmental considerations and reducing their carbon footprint are prime motivators for many people. Or, if you live in an area with a greater potential for service disruptions, is safety and security for your family paramount?

What about being able to help support the electrical grid? Homeowners with rooftop solar willing to share their battery-stored power with the grid could qualify for state-funded rebates. And, new bi-directional electric vehicle (EV) chargers allow an EV to send energy back to your home (V2H – vehicle-to-home) or to the grid (V2G – vehicle-to-grid). Porsche recently conducted a pilot program, pooling multiple Taycan’s sending power back to the grid, proving the potential to transform methods to store and generate energy in the future. For utilities, battery storage and new bi-directional chargers hold the potential for a more stable and lower-carbon electrical grid in the future.

System Sizing and Design

One of the more challenging aspects of determining your battery needs is understanding how to size the system properly. The amount of power that a battery can store, measured in kilowatt-hours, will be critical in your calculations. We highly recommend engaging with a professional, experienced installer when contemplating a solar system. Be sure to discuss the amount of energy to be used each day, the amount to be reserved for use in an emergency, and how much battery capacity is required for utility cost reduction. Provide your installer a list of appliances and devices in your home and their power and energy requirements.

If you continuously use the solar energy stored in your batteries to offset higher-cost energy from your utility during peak hours, there will be less stored energy in your batteries in a grid disruption. The solar monitors in battery storage systems allow you to regulate your daily energy use versus how much you reserve for backup power. The more you reserve, the less you can use to offset costs.

The size of your battery bank is based on how much power you’ll need daily, measured in kilowatt-hours per day. The typical US home consumes nearly thirty kilowatt-hours per day, yet the average solar backup battery stores only about 10 kilowatt-hours, creating a potential issue during extended outages. Fortunately, most battery brands are stackable, with limitations, allowing you to link or string batteries in a bank to increase storage capacity. Also, your rooftop solar panels deliver power to your home and recharge your battery during the day to continuously regenerate your backup power.

In an emergency, the prudent approach to energy management is conserving as much energy as possible. You’ll need to cut back on your usage to optimize stored energy. Prioritize essential appliances and communication devices and discuss creating an emergency subset circuit with your installer.

Finally, battery makers are beginning to offer smart panels and apps. For example, Tesla has a mobile app, the same one used for your Tesla S EV, that allows you to monitor your home’s energy production and consumption in real-time. You can see your solar system’s status, state of charge, and set your preferences to optimize energy usage during an outage. You can also use the app to reduce or eliminate your electricity expenses, toggling individual circuits on and off remotely to avoid consumption during peak rates.

Financing Your System

Even with declining costs, going solar is still a significant investment. The cost of an average-sized residential system has dropped from $40,000 in 2010 to roughly $20,000 today, pre-incentives. In Arizona, solar system costs are between $2,800 and $3,200 per kilowatt – a typical 6kW system is usually between $17,000 and $20,000. In California, expect to pay 20% to 30% more. Fortunately, unlike a depreciating asset, your solar system pays you monthly through reduced energy expenditures. It then pays a handsome dividend when you sell your home.

For most homeowners, if you can afford your current monthly utility bill, you can afford to go solar. You have options if the cost of entry is a concern; there are zero-down solar loans and zero-down leases that require no initial out-of-pocket expenses, making it easy for homeowners with good credit to start generating immediate savings.

Although we mention leases, owning your system is the best way to access the savings, benefits, and return on your solar investment. Both options reduce your carbon footprint and benefit the environment; however, you own the system and earn the federal tax credits and other rebates and incentives with ownership.

Financing options include cash, which provides the most significant savings and optimizes the ROI. The next most preferable option is a HELOC or Home Equity Line of Credit. In a HELOC, your home serves as the collateral, and the interest on this type of loan becomes tax-deductible.  Other solar loans are secured or unsecured (not protected by collateral) available from local and national banks, credit unions, and specialty solar financing companies. Your installer should be able to provide a list of resources.

In December 2020, the Investment Tax Credit (ITC), set to decline in 2022, was extended through 2023. In addition, it is anticipated that ITC and Production Tax credits will be extended even further. Other credits and incentives vary by state and utility company. Arizona has dozens of financial incentives, rebates, and loan programs for commercial and residential sectors. A knowledgeable and local installer will be aware of these state, local, municipal, and utility incentives. However, to be prudent, always check with your financial consultant or tax professional to determine if you qualify.

In Summary

We hope this article has exhibited the importance of solar battery storage for your home and its potential as a virtual power plant for utilities. Solar is a savvy investment for the homeowner financially now and in the future, and environmentally. We envision a day in the not too distant future when rooftop solar with battery backup will help solve our energy problems – powering your home, charging up your batteries during the day, and allowing the utilities to draw on it as needed while earning a rebate!

PEP Solar

If you’re curious about what solar can do for you, we hope this article has been helpful, informative, and at least a bit persuasive.

We’re Phoenix Energy Products™, LLC, doing business as PEP Solar. In business since 1978, we are the oldest residential solar installer in America. We are a full-service solar company installing, servicing, inspecting, and repairing solar for homeowners. Our mission is to provide complete solar power solutions that perform beyond your expectations for the life of your system.

We are a privately owned, Arizona-based company and pride ourselves on delivering appropriately sized systems to meet your goals.

We would love to help you design and install your solar PV system using the best products in the solar energy market. At PEP Solar, we partner with only the best solar equipment providers to deliver your best solar solution.

For more expert information on all things solar, visit us online at pepsolar.com or contact us at: (623) 806-8806.

PEP SOLAR

2025 W Deer Valley Rd | Suite 104

Phoenix, AZ 85027





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