Will Solar Batteries Continue Working During Long Outages?

Battery Backup
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How Long Solar Batteries Last in a Prolonged Power Outage

Will solar batteries continue working during prolonged outages? The short answer: it depends. The capacity of the solar battery and a homeowner’s electricity needs determine a battery’s staying power. In any case, investing in a solar battery means less reliance on the grid.

Why Solar Homes Need Battery Backup

During a power outage, the electrical grid shuts down. New federal rules in the 2017 edition of the National Electrical Code (NEC 2017) require grid-connected solar panel systems to shut down immediately at the modular level during an outage. This means solar panels stop working too. This requirement protects utility company technicians from possible electrocution while working on damaged power lines. It also safeguards firefighters who may have to enter a solar home through the roof. However, the requirement poses a problem for solar homeowners who lack battery backup.

When Solar Panels Generate Electricity

Solar arrays work because UV rays from the sun reach a home’s solar modules, which convert that energy into electrical power. This energy-conserving process depends on the sun, preventing solar panels from generating electricity at night. Many solar homeowners remain connected to the grid, enabling them to draw power from the grid at night and to sell or receive credit for any excess solar energy generated and sent back onto the grid during the day. In the past, solar panels could continue to produce electricity during a daytime power outage, but the new federal rules (NEC 2017) prevent this.

Grid-Tied Transfer Switch Requirements

Before NEC 2017, solar homeowners still were required to shut off power or redirect it away from the grid during an outage, but a complete shutdown of solar panels wasn’t required. Solar homes could continue generating power during the day, and solar homes with battery backup could continue drawing solar-generated power at night.

Under the current rules, however, the only way homeowners can benefit from solar-generating capacity during an outage is to invest in solar storage. The rapid shutdown requirement calls for all conductors within a foot of an array to reduce to 80 volts in fewer than 30 seconds. The high-quality inverter Go Solar Group installs for its customers, the SolarEdge can also be turned off manually at the bottom.

How Long Will a Battery System Last?

The new rapid shutdown requirements have made backup batteries more important than ever. Homeowners need to know a battery’s capacity or the amount of usable energy from a single charge. Customers also should ask about a battery’s projected lifespan and how long it takes to discharge.

The lifespan of a solar battery depends on whether it needs priming or is exposed regularly to extreme temperatures. However, solar battery lifespans typically range between 5 and 15 years, and they are expected to increase as technology improves. The duration of solar battery discharge depends on the amount and rate of the drawdown and the capacity of the battery.

Average Power Outage Length and Usage Needs of Homeowners

Power outages in the United States vary in duration. In 2018, the average power outage for U.S. electricity consumers lasted 5.8 hours. Of course, a variety of factors, such as weather and utility practices, influence the length of outages. In any case, 5.8 hours is a significant length of time — long enough for refrigerated food to spoil and a home’s occupants to become uncomfortable in cold or hot weather. All this makes energy storage options worth considering. Determining how much battery backup your home will need during an outage depends on how much power you consume, the likely duration of the outage, and the climate. One emergency battery is enough for some homeowners, while others require two or more home batteries to meet their energy needs.

Solar Battery Capacity

The capacity of a battery measures how much power it will store and later provide. Matching a solar battery with a homeowner’s needs will help ensure that enough electricity is available during an outage. Go Solar Group offers three different battery backup options, enabling homeowners to tailor their energy storage to their home’s needs.

Battery Backup Options for Prolonged Outages

Go Solar Group’s Level One backup has two options, each with portable features that make them easy to bring along on trips. The Goal Zero Yeti 1500 will sustain power for a half-day. The Yeti 3000 can provide power for one or two days, depending on the wattage-per-hour rate of use. Both are lithium-ion batteries, which are lighter and have a longer lifespan than lead-acid batteries. For longer power outages, we recommend our second-level battery backup. The Goal Zero Yeti Tank, a lead-acid battery, and the Yeti Link, a lithium-ion expansion module, provide an extra 1,250 watt-hours, or 12 hours of energy at a 100 watts-per-hour usage rate.

Using a Tesla Powerwall During an Outage

Our third and most powerful option is the Tesla Powerwall, the most efficient and cost-effective home battery on the market. The Powerwall, a stationary lithium-ion unit, contains a cooling liquid to regulate temperature and avoid overheating. To power an entire home or to guard against prolonged outages, some homeowners install two or more Powerwalls.

Emergency Battery Backup and Portable Solar

Another way to draw on solar power during an outage is to invest in a portable solar panel. These units complement a home solar array nicely, prolonging the life of backup batteries during an outage. Our portable solar options include foldable solar panels, which can be placed in a sunny spot for charging a backup battery during the day. They come in a variety of sizes and generate as much as 200 watts per hour.


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