Does solar work in a blackout?

If you are thinking about installing a solar energy system to have power in a blackout, there are some facts you need to consider. There are many advantages to installing a grid-connected solar energy system, but having full power to your home or business during a blackout is not one of them. Solar in a blackout does not solve that problem unless special steps are taken.


NYC during a blackout

In the event of a power outage, basic habits such as charging a cell phone or powering a small fan or space heater become essential. Most homeowners have no source of backup power when the grid goes down. Even homes with solar may lose power in the event of a grid outage if their system does not include some form of energy storage.

Does solar work in a power outage?

There are two reasons that ordinary grid-tied solar will not work during a grid failure. The first is a technical reason and the second is a safety and regulatory issue.

First and foremost is the technical reason. The electronics that control a solar electric system constantly adjust voltage and current in order to keep the panels operating at their most efficient and powerful operating point through a range of varying sunlight conditions. To do this, the system needs to be able to produce quantities of power that are not dependent on how much your house is actually using at the time. In a grid-connected system, that excess power is put back onto the grid for others to use, and your utility credits you on your bill for that power.

Solar power output varies directly with sunlight levels. So, even if you disregard the need for efficiency, connecting this variable resource directly to your home’s electrical system would cause your lights to blink, damage your refrigerator, and wreak havoc on your computers and television.

The second reason that solar shuts down during a blackout is safety.

During a power outage, the power utility sends out repair crews to find and fix the points of failure. The linemen and women can be jeopardized if there is a local power generator (like a solar array) leaking power onto the grid lines. Therefore, utility rules mandate that in the event of a power outage, solar arrays must automatically shut down. Solar systems have detectors that sense whether power is coming across the grid, and whenever grid power is down, they automatically shut down too, to protect utility workers.

Battery Backup

There are arguments for and against battery storage for PV solar systems. The biggest “for” argument is that, with battery backup, your home or business can be powered during a blackout. The biggest “against” of battery storage is the cost, which can double the cost of your clean energy system. Batteries also compromise the “clean energy” aspect of solar—they are toxic and very costly to discard when no longer useful. Batteries have a relatively short life, compared to other solar system components; they are also very heavy and bulky, and require a lot of maintenance to perform at their best.

New inverters offer some solar power in a blackout

We have been using SMA inverters for a long time—they are great products with high reliability.

Now, new technology developed for SMA’s Sunny Boy 3000TL-US/4000TL-US/5000TL-US models offers a partial solution to the grid power failure problem. These new inverters feature a secure power supply (SPS) that can connect to an external socket outlet and provide up to 1,500W of daytime power—when the sun is shining and the array is generating sufficient power—in the event of a grid outage. This gives customers confidence that they can get a small supply of electricity from their solar inverter even when the grid is out and other solar PV systems are down. The bottom line is, with new technology, grid-connected solar can deliver a limited amount of electricity to your home or business during a power outage. This is a new development.

These new inverters address both of the technical and safety issues by creating a small, independent circuit entirely disconnected from the grid. The inverter controls the solar panel electrical output as an alternative to sending out variable power levels.

The SMA inverters represent a convenient compromise between many solar owner’s desires for backup power and their reluctance to make the large upfront investment in a full battery backup solution.

Is solar worth the money?

The ability to generate and use a limited amount of clean solar power during a blackout adds to the other advantages of going solar.

  • In the long run, solar power is economical. Solar panels and installation involve high initial expenses, but this cost is soon offset by savings on energy bills.
  • Solar can increase the value of your home.
  • With a grid connection and net-metering rules, your solar power system can generate clean energy and share it with the grid.
  • Federal tax credits can offset 30% of your investment.
  • Solar energy systems are safe, reliable, and durable—the panels are warranted for 25 years.

Once your initial investment in solar is paid off, the fuel is free. With fossil fuel costs and utility rates predicted to rise, solar can be a good way to lock in long-term savings now.

6 replies
  1. miriam
    miriam says:

    “A small amount” of electricity—exactly how much are we talking, here? Our outage needs are, as follows, in order of importance:

    1) Air conditioning, mainly at night, in order to sleep
    2) Freezer/refrigerator, at least enough hours to run in order to keep stored goods frozen as long as we don’t open the door during the outage.
    3) Daytime fans to set in windows to pull cooler outside air into house and circulate it.
    4) Cellphone recharger, AA, D-type battery rechargers.

    If we had those services, we know from experience that we could exist for weeks at a time with no electrical service from the utility company. We would not run our central a/c unit, but a small window unit.

  2. Derek
    Derek says:

    I have recently bought a house that is solar powered ans no nothing of how it works. What do I have to do it a black out? will it automaticly shut it;s self down? when power is restored what do i do? If I have repairs done to the electrical wiring do I have to isolate the solar system If so how is this done. Thanks

  3. Bailey Shooner
    Bailey Shooner says:

    Hi Derek, congratulations on your new solar-equipped home! Assuming your home is grid-tied (meaning you feed energy to the grid and draw when your demands exceed your solar output), if there is a black-out, your system will automatically shut down. You do not need to do anything, as your system would have been installed with an automatic disconnect that shuts your system down for you when the grid goes down. The reason this is necessary is so that your system is not feeding live power onto the grid when people may be working on the lines. When power is restored, your system should automatically turn back on within a few minutes.
    In regards to whether or not you need to isolate your solar system when electrical wiring repairs are being done: your electrician would probably know this, but they would want to shut off the inverter, which effectively shuts off your system so it is safe to do the electrical work. If you (or your electrician) still have questions or you ever consider expanding your system, please give us a call!

  4. william
    william says:

    have solar and backup generator with lock out when grid is down can I also run solar in combination with generator safely. bill

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