What happens if you have solar and the power goes out?

Updated

how to survive a power outage with solar power
Image source: Steiner Electric

So you’ve got some shiny solar panels on your roof and you’re making a lot of your own electricity. Your power bills are nearly eliminated and you’re feeling like an environmental champion. Then one windy night, a storm blows down a huge tree on your block and the power goes out. When the morning sun shines over the horizon, will your refrigerator be running? Probably not.

If you have solar panels on your roof, you’re most likely connected to the electric grid in your area. That means you draw power from the utility company at night, and when your panels can’t make as much energy as you need at any given time. You also send power to the grid when your panels produce more than you need. 

When the power goes out, most home solar installations are designed to shut down in order to stop them from feeding power back into the very wires that might be the source of the outage. After all, you don’t want your solar panels to be the reason utility workers are injured by live voltage in downed power lines. 

But what good are solar panels on a roof if they can’t make electricity? There’s got to be a way to keep the power on, right? What about batteries, or preventing solar energy from flowing to the grid when it’s down? Read on to discover the answers to these questions.

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    Why don’t solar panels work in a blackout?

    Most homeowners with solar on their homes have what is called a “grid-tied” solar system, which means the panels are connected to an inverter. 

    The inverter is connected to the main AC panel in the house and to a special smart electric meter that records both energy you use from the utility company and energy sent to the grid by your solar panels. Grid-tied solar systems work without any battery backup equipment.

    That’s why home solar people generally say “the grid is your battery.” When your solar system produces excess energy, you’re sending it out to your neighbors and getting credit for it (under net metering), but when the sun goes down, you still need grid power from the utility company. If you play this balancing act just right, you can have a power bill near $0. 

    In the event of a blackout, a typical grid-tied system has a special automatic shut-off in order to prevent that extra energy from being sent over possibly-damaged power lines. It’s a safety feature intended to protect the line workers who go out to fix things when they break.

    But that also means your house doesn’t get the solar power, either. In a blackout situation, the power from your solar panels goes nowhere - unless you have some way of storing the electricity (with a battery) or otherwise cutting your system off from the grid.

    How can you use solar power to survive a power outage?

    If you want to keep your home up and running when the power goes out, there are a few ways to do so:

    1. Use a backup gas generator
    2. Add solar batteries to your system
    3. Use a solar-powered generator
    4. Replace your inverter with a Sunny Boy or Enphase Ensemble system

    1. Backup gas generator

    We solar-lovers don’t generally advocate burning things to make power, but the cheapest way to make sure you’ve got backup power in the event of a blackout is to buy a generator.

    duro-max gas generatorFor a little more than a thousand bucks—plus the cost of fuel and installing an external electrical plug—you can get a 9,000-plus-watt gas generator that can mostly run your whole house while the utility workers bring the grid back online. 

    With your generator and some fuel, you can usually outlast any prolonged outage of the grid, and even help a neighbor out if you need to. Your solar panels will remain off until the grid comes back up, but at least you’ll have power.

    Cons of a backup gas generator

    Gas generators tend to be loud, smell bad, and create all kinds of pollution from their use. Can you imagine the sound and smell if you and your ten closest neighbors all run your generators at the same time? 

    There’s also the risk of a fire starting due to stored fuel igniting or burning up when you refill near the hot metal parts of a long-running generator, which certainly doesn’t help matters if your power gets shut off because of increased fire risk.

    Of course, cleaner generators exist, running quieter on diesel or natural gas, but the price goes up very quickly for anything more than the basic version. Also, events during the Texas power outage in February 2021 show how natural gas can also be a very unreliable fuel, at least in blackouts caused by winter weather. 

    Bottom line: generators are not a great option other than their low cost. Let’s look at some purely solar options, including so-called solar generators, in the section below!

    2. Solar battery

    For true peace of mind during a power outage, you can’t beat a solar battery system

    There is nothing quite like the feeling of being the only house on the block with the lights on after the grid goes down—although the more altruistic among us would prefer that all our neighbors had the same luxury. With a solar battery, the transition from grid to battery backup power is seamless and reassuring.

    Many options are available, from a bank of deep cycle lead acid batteries to the sleek, easy-to-use Tesla Powerwall. These days, solar installers have lots of expertise installing batteries alongside solar installations, and you might be surprised at the number and variety of Powerwall alternatives in the marketplace. 

    solar batteries

    If you have your heart set on Tesla, you will find many installers who are certified to install them. If you are open minded about your options, there are a number of batteries from companies like LG and sonnen that compete with Tesla in terms of functionality and price.

    Unlike solar without batteries (i.e. a grid-tied solar system), a solar-plus-battery installation keeps your power on by “islanding,” or disconnecting itself from the grid when an outage is detected. While the blackout remains in effect, your little solar island will charge the batteries during the day and discharge them at night. As long as you have enough battery capacity, you could keep running like this through a very long power outage. 

    Find out if installing solar + battery storage is worth it for your specific home

    3. Solar generator

    If you’re not quite ready for the multi-thousand dollar commitment of a whole-house solar battery, there are also “solar generators” from companies like Renogy and Goal Zero available for a few hundred dollars that can at least keep your food cold and a space heater running. 

    Just keep in mind that these portable options can be charged with or without solar panels while the grid is up, but again, they won’t charge from solar when the grid is down without the same kind of special equipment used for a full solar-plus-storage system.

    Learn more: Pros and cons of solar generators

    4. A special inverter or inverter system

    Luckily, there is a way for a homeowner with solar to use the energy their panels make without a connection to the grid or an energy storage setup. 

    SMA and Enphase are two companies that make special solar inverters that are designed to automatically disconnect from the grid in the event of an outage, while still providing power to your home from your solar panels.

    SMA Sunny Boy Secure Power Supply

    While most solar inverters have that automatic shut-off we discussed above, SMA Sunny Boy inverters can be installed with a special circuit that allows homeowners to switch over to pure solar power after a power outage.

    sma sunny boy inverter

    The Sunny Boy inverter can only produce up to 2,000 watts of “opportunity power” at a time, and it’s designed to shut down if the power draw is too great. Note, it only works if the sun is up.

    2,000 watts might sound like a lot (20 100-watt light bulbs!), but it probably isn’t enough to start an air conditioner. Opportunity power is designed for essential appliances only. Realistically, you can probably plug in your fridge and a lamp along with a TV and your smartphone to keep you company.

    The total cost for the Sunny Boy and the outlet might be $1,000 more than another brand of inverter without the backup feature. But factored over a 10-year span (the life of the inverter), you might find this an attractive option.

    Enphase Ensemble 

    Another company that has put a lot of work into making solar work when the grid goes down is Enphase. The company’s Ensemble energy management system works together with its microinverters to provide “grid-agnostic” solar power. That means it can send power to your appliances from your solar panels as long as the sun is shining brightly enough, even without batteries. 

    Of course, Enphase would much prefer you purchase its energy storage solution along with the Ensemble system, which would mean your home could operate during all parts of the day from stored solar energy. And if you’re willing to pay several thousand dollars extra for Enpahse’s IQ7 microinverters and the Ensemble system, you might be willing to drop an extra couple G’s for the battery.

    Why not go off-grid?

    People who want to get off fossil fuels completely and ensure that only clean energy passes through their wires might be tempted to go off-grid completely. And that certainly is an option, but it can be a very costly one. 

    Though going solar has never been less expensive than it is now, it’s still a financial commitment - and choosing an off-grid solar setup can get very expensive. Even a small off-grid solar system with battery storage will cost many thousands of dollars more than a grid-tied system, simply because the hardware needed to make it all work costs so much. 

    In addition, off-grid battery storage needs to be able to provide the correct amount of electricity you might need over the course of three cloudy, snowy days during the coldest part of the winter wherever you live. It’s overkill in the sunnier months, but you don’t want to get caught without enough power, and then have to resort to a fossil fuel generator. That puts you right back at square one.

    Find out how much you can save this year by switching to solar

    Key takeaways

    • A typical home solar installation is designed to shut down during a power outage to protect utility workers and prevent the grid from running at low efficiency.
    • To keep power on during a blackout, add a backup generator, solar batteries, or a new kind of solar inverter that can offer some power to keep essential appliances running.
    • Each of the options listed above has tradeoffs. The cheapest options are dirty and polluting, while the best options are pretty expensive.
    • Nothing beats the peace of mind of whole-home battery backup. There are many options to choose from, from the Tesla Powerwall to batteries from sonnen and LG.
     - Author of Solar Reviews

    Ben Zientara

    Solar Policy Analyst and Researcher

    Ben is a writer, researcher, and data analysis expert who has worked for clients in the sustainability, public administration, and clean energy sectors.

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