Home solar energy systems are often sold as a way to gain energy independence, but does a rooftop array really keep your home humming during power outages?
Many homeowners ask the same thing, especially in states with a stressed grid (looking at you, California and Texas): If I install solar, will my lights stay on in a blackout?
The quick answer is, no, probably not.
In most cases, installing home solar won’t keep your lights on if the main energy grid fails. This might seem counterintuitive in a heat wave where the sun is still shining. After all, if your rooftop panels are producing energy, why wouldn’t your home still have power?
See also: The best solar panels for home use
Here’s why and what to do to keep the lights on in a power outage.
Why home solar won’t usually keep your lights on during a blackout
Most home solar energy systems are grid-tied, meaning they send and draw energy to and from the grid as needed and when safe to do so. If there’s a grid outage, your solar panels are prevented by safety switches from sending energy to the grid. This is the case even if conditions are right for your panels t still produce energy, i.e., if it’s not nighttime or super cloudy.
The main reason for this cessation of electrical output is to ensure the safety of the power grid and nearby workers. After all, if workers trying to fix power lines think there’s no juice running through those lines, but your home solar energy system is, in fact, sending electricity through the lines, that’s a real problem for those linesmen. Homeowners who don’t have the right safety set-up and an interconnection agreement with a utility pose a risk of electrocution to workers and themselves, electrical fire, and damage to the grid infrastructure and their home and personal property.
This is one reason why getting a properly designed solar energy system is imperative. As is having the system properly inspected by the utility whose power network you’re connecting to, assuming you’re installing a grid-tied system.
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How to go solar and keep the lights on during a blackout
Given that going solar at home is meant to restore energy independence, it’s not surprising that many homeowners want to keep the lights on even in a blackout. There are a few ways to do this:
- Install a backup battery storage system and critical load panel or smart electrical panel
- Don’t connect to the grid in the first place
- Install a generator that works with your home energy system
- Set up a simple DC circuit
These options aren’t mutually exclusive. For instance, you can install an off-grid system plus battery storage plus a backup generator. Or, you could be grid-tied with battery storage, grid-tied with a generator, or grid-tied with both. And you can set up a DC circuit with any and all of the other options.
The trick here is to make sure the electrical panel in your home is correctly wired to keep everyone (and your property) safe. Improper wiring can result in equipment shorting out, not working at all, rapid battery degradation, and safety issues for you, electricians working on your home, and power grid workers.
How to set up your home solar energy system for backup power in a blackout
Let’s say you’re installing a rooftop solar array and you want to be able to keep the lights on in a blackout. To do this, you’ll need to install backup batteries and a charge controller between the inverter and the DC disconnect.
What is a charge controller? Charge controllers are an absolute must for any home solar installation with battery storage. A charge controller monitors battery voltage and protects the battery from overcharging. A charge controllers is also known as a high-voltage disconnector. This is because a charge controller disconnects or interrupts the flow of electricity from a photovoltaic array if it detects that the battery is fully charged.
Most grid-connected systems are required to have two ‘disconnects’. These safety switches can be flipped to prevent electrical shocks when homeowners or service personnel are working on the solar electrical system. One disconnect is located between the solar array and the inverter. This allows you to safely service your inverter while still drawing power from the grid.
The second disconnect cuts the flow of current between the inverter and the main service panel. When this happens, there is no AC flowing into the electrical circuits powering your home from your solar panels, but you can still run some appliances and lighting on DC if you have set up a separate circuit (more on this below!).
Smart electrical panels and critical load
To ensure your home has at least some power during a blackout or brownout, you’ll want to install a critical load panel or smart electrical panel. Most home battery storage systems aren’t big enough to run all the appliances and loads in your home. And even if they can run a maintenance load, they may not have the start-up power necessary for major appliances like an A/C.
A critical load panel is a secondary electrical panel containing essential electrical circuits. A qualified electrician can pull these circuits into the new panel, then set things up so this panel alone is powered by your backup battery or generator in case of emergency and grid outage.
A critical load panel is fairly straightforward but best to install as part of your home solar installation. A smart electrical panel is more complicated and more expensive but offers a lot more flexibility and ease of use for the average homeowner. This kind of panel allows you to get the most out of your battery storage system as it can provide circuit-level monitoring and controls. This way, you can easily choose which circuits are powered by your home solar and backup battery system in an outage and which you want to turn off to save energy.
A smart electrical panel helps to futureproof your home. Instead of having to decide now which circuits and appliances you might want to run in a power outage in a decade or two, a smart panel gives you the flexibility to make those decisions in real-time as needed.
After all, power outages aren’t just inconvenient. They could mean your home becomes dangerously hot or cold, can lead to burst pipes, and can mean you can’t power essential medical equipment or mobility equipment, creating a risk of injury, sickness, and even death.
Home solar with storage and a generator
Whether you decide to go off-grid or grid-tied, it’s a good idea to hook up a backup generator to your home energy system if you live somewhere remote and prone to blackouts. With a stand-alone system, your generator will connect to the battery bank to charge it up when stored capacity runs low.
A backup generator can also help perform routine battery maintenance, i.e., equalization. This may be necessary with some batteries to keep them in good condition.
With an off-grid or on-grid system, homeowners can also consider installing a wind turbine or microhydro system as an extra source of energy. These may well work even when the sun isn’t shine and the grid is down.
These same disconnects or safety switches are required in stand-alone systems not tied to the grid. After all, you still want to be able to safely service the electrical system and not get electrocuted by your solar panels’ output. Some stand-alone systems also include a low-voltage disconnect (a second charge controller) that can cut the flow of electricity from the battery to the inverter if it detects low voltage in the battery. This is designed to protect against over-discharging, or draining the batteries too much and causing damage.
The main downsides to going off-grid entirely are that you have no outsourced backup energy source, i.e., the grid if your home energy system fails. You will also usually have to over-build your energy production system and storage capacity. This means you’ll pay far more for a larger array and more battery storage off-grid than on-grid.
Battery options and costs
There are now several options for home solar energy storage battery systems. Your best bet for battery storage is to include this as part of your home solar installation. That way, you benefit from efficiencies as you already have electrical contractors on site. You may also be able to access discounts if you choose certain battery brands alongside solar panel brands. For instance, a SunPower plus SunVault installation or Tesla solar roof with PowerWall.
In general, expect to pay the following for these top of the line home solar battery storage options:
- Generac PWRcell – $9,999
- LG Chem RESU – $9,500 to $13,000 (including installation)
- Panasonic Evervolt – $15,000 to $20,000 (including installation)
- Sonnen eco – $10,000
- Tesla PowerWall – $8,500
Tesla, Panasonic, and LG Chem all make their batteries in the U.S. This may mean they qualify for greater tax incentives in certain places. As with solar panel installations, solar storage is now eligible for the 30% federal solar investment tax credit. This can help cut the cost of your entire installation significantly, assuming you have the tax burden to maximize use of the credit.
Set up a DC circuit
One of the simplest ways to keep at least some lights on during a power outage is to install a DC circuit. This circuit runs between the solar array and the inverter, meaning you can still use the energy flowing out of your array even if the inverter malfunctions or grid power goes out.
You can even use the direct current (DC) produced by your home solar array to power some appliances. And this is actually even more energy efficient than converting all your electrical output to alternating current (AC), where you lose about 10% of the energy.
Some things that you can run on DC alone include water pumps, some consumer electronics, and even certain refrigerators, ceiling fans, and other appliances. You’ll need to check which appliances are safe to run on DC first, or consider having backup DC-only appliances for emergencies.
Not sure about running appliances on DC? It’s still smart to have at least one DC circuit at home. This way, you can power a few lights from your home solar array in an emergency. This includes powering a lightbulb right by your inverter, in case it stops working and you need light to service it!
Why get backup solar storage batteries?
More homeowners than ever are installing backup batteries when going solar. This is for a variety of reasons, including greater vulnerability in the electrical grid, the availability of the solar tax credit for solar storage batteries, and much lower prices for batteries than in years past.
Solar installer SunRun noted a 100% increase in the demand for solar installations with battery storage in 2021 versus 2020. SunPower reported 27% of its solar customers purchasing battery storage and Tesla announced in 2021 that Tesla Roof customers would have to include solar storage as part of their installation.
In general, if any of the following apply to you, solar storage batteries are a good idea as part of your home solar energy system:
- Frequent electricity outages
- Less than generous net metering rules (or no net metering)
- Time-of-use electricity tariff
- Demand charges on your bill.
With a solar array and backup battery system, your home’s electrical circuits draw on the available energy produced by the array during the day. Any excess electricity is stored in the batteries for use overnight or when it’s cloudy. This kind of system has the advantage of avoiding sending all excess energy to the electrical grid. In most places, the utility charges more for electricity drawn from the grid than it pays for electricity fed into the grid.
Not all home solar systems are set up to draw from the battery overnight, however. Talk to your solar installer and electrician to ensure your battery is going to do what you want it to do. Typically, a home solar battery storage system will cost around $10,000-$20,000 with installation. With the federal solar tax credit now covering storage, though, and many state, local, and utility incentives for storage, the payback period is now quite short for battery backup. And, of course, the peace of mind in a power outage is priceless.