It’s a bummer that most homeowners don’t realize until after they’ve committed to buying rooftop solar panels: When the power goes out — after a hurricane, a violent thunderstorm, or when a tree falls on distribution lines — so does your grid-connected rooftop solar system.
It turns out that while solar systems can generate as much power as most homes consume on bright, sunny days, they cannot be relied upon to consistently produce the amounts that we need. Clouds, rainstorms, and changing angles of the sun can all reduce your system’s generating capacity.
“Ninety-nine percent of prospective solar customers I speak to are surprised when I tell them,” says Justin Hoysradt, owner of the West Palm Beach-based solar installation company Vinyasun. “Intellectually, it doesn’t make sense. The sun is out. They can make electricity. Why can’t it work when the power is out?”
To overcome this shortcoming, homes with rooftop solar systems must be connected to the utility grid. But to keep the grid safe during outages, utilities require rooftop solar systems to shut down when the grid goes down.
Many solar owners had different expectations. So in recent years, several innovative companies have developed workarounds — pricey add-ons that enable solar panels to keep food cold, devices charged and some lights on as long as the sun is shining.
But to keep your house functioning as normal — with full use of your air conditioner, water heater, washer and dryer, computers, TVs, fridges and stove — you’ll have to spend $16,000 or more for storage batteries.
Having a backup power generation source is typically not the primary reason that a homeowner would purchase a rooftop solar system, industry leaders say. Many install solar because they want to help fight climate change by converting to renewable energy. Others hope to reduce or nearly eliminate their electric utility bills.
To also be able to generate power after a storm passes would be a fringe benefit, or a kind or insurance policy preferable to hooking up to a noisy gasoline-powered backup generator. Unfortunately, it’s not that simple, Hoysradt and other solar installers say.
The vast majority of rooftop solar systems are also tied to the electrical grid for a couple of key reasons: One, without backup batteries, solar owners must draw power from their electric utility at night and on days with heavy cloud cover.
Two, solar owners can cut their utility costs by selling back to the grid any excess power their solar panels generate during daylight hours — an arrangement called net metering. But to paraphrase the creators of Spiderman, with great benefits come great responsibility: Solar power systems connected to the grid must have a way to prevent power from backfeeding to the grid during outages and potentially injuring line workers making repairs. And so modern electrical codes require rooftop solar systems to shut down along with the grid when an outage is detected.
Still, rooftop solar owner have options for keeping power flowing in their house until the grid comes back on. In a recent blog post, the consumer-focused website solarreviews.com identified four ways to stay powered during an outage.
Option One: Gas Generator
The cheapest and simplest option is to forget your solar panels and just buy a tried-and-true gasoline-powered generator, the post said, even if “we solar owners don’t generally advocate burning things to make power.”
You can spend a few hundred dollars on a small gas generator that will run a few things, or invest thousands in a permanent whole-house generator that runs on natural gas and automatically fires up when needed. A generator that produces at least 9,000 watts and can power most of your house will cost you about $1,400, not including fuel and the cord needed to connect the generator to the home.
To comply with electrical codes, using a generator to power a central air conditioning system and other appliances requires paying an electrician to install a transfer switch. The switch will ensure the house is disconnected from the grid and cannot backfeed power when the generator is plugged in.
Some generator owners will connect to the house by plugging into the outlet used by their clothes dryer. But for this to be safe, utility power must be disconnected from the home at the main breaker. Failure to do so can result in tragic consequences if the grid power returns while a generator is powering the home. Plus, this method violates electrical codes and your insurance company might refuse to cover resulting damage.
With a gas generator, you’ll have power but your generator-less neighbors might hate you. Gas generators are “loud, smell bad, and create all kinds of pollution,” the post points out, adding, “Can you imagine the sound and smell if you and your 10 closest neighbors all run generators at the same time?”
Cleaner and quieter generators run by natural gas or diesel fuel exist but cost more, the authors point out. Whole-home generators are a pricey but less labor-intensive choice. They can be installed permanently outside the home and run on liquid propane or natural gas. Prices typically start in the $5,000 to $6,000 range.
Option Two: Solar Generator
Portable solar generators by companies like Renogy and Goal Zero are another option starting at just a few hundred dollars and typically costing about $2,000, Solar Views said. They are quiet, clean and don’t require fuel or motor oil. But they can only power a handful of electric conveniences.
They consist of a small portable solar panel that feeds power to a battery connected to an inverter. Owners can plug phones, tablets, mini-fridges and cookstoves into the inverter and enjoy a limited amount of power, but not enough to power an air conditioning system.
Option Three: Special Solar Inverters
Demands by rooftop solar owners to use their panels during grid outages led to development of special solar inverters that not only automatically disconnect the house when the grid goes down, but can also be switched over to provide solar power to essential appliances during the outage, Hoysradt said.
Brands that accomplish this include SMA Solar’s Sunny Boy, which will cost about $1,000 more than the required standard inverter. The Sunny Boy can send up to 2,000 watts (or 2 kW) of solar-generated power at a time to its own connected outlet. Owners can use extension cords to plug essential devices into the outlet and the inverter is designed to shut down if the power draw is too great. Another brand is Enphase Lab, which makes a system it calls Sunlight Backup.
Both systems only work when the sun is out, but with Sunlight Backup, power flows to your home’s existing circuits and you can select which ones get top priority when passing clouds reduce the amount of electricity generated by your solar panels.
At about $4,000 to $5,000, the Sunlight Backup is considerably more expensive than SMA Sunny Boy because it requires separate microinverters for each solar panel, plus a load controller to regulate power flow to specific circuits in your home, according to Enphase Lab’s website. Again, neither will run a central air conditioner.
“Realistically, you can probably plug in your fridge and a lamp along with a TV and your smartphone to keep you company,” Solar Reviews said of the Sunlight Backup.
Option Four: Storage Batteries
Solar owners willing to spend several thousands of dollars on special inverters that provide limited power to their homes often decide to just go the rest of the way and buy storage batteries to ensure they’ll have full continuous power regardless of the time of day or weather.
Storage batteries capture excess power generated by solar panels on sunny days, and if needed, can be topped off with utility power from the grid. At night, your house runs on stored solar power instead of power purchased from the grid, dropping your monthly power bill to the utility’s minimum connection charge of around $30 a month.
And that fringe benefit discussed earlier in this story? A solar system with storage batteries can power your house for several days during a prolonged grid outage.
Prices for storage batteries depend on the type of chemistry involved, but most residential solar systems use lithium ion batteries, which can cost around $8,000 to $12,000 each, according to Solar Reviews. A single storage battery will not power everything in your house, so if you want to use your air conditioner after an outage, you’ll need two or more, Hoysradt says.
That can add quite a bit of cost to a rooftop solar system that typically costs around $20,000, but if having a whole-house backup energy generation system after a hurricane is one of your main reasons for getting solar, there’s no other way around it. And you can cut costs by buying everything at once and take a 30% federal tax credit on the entire purchase.
You can take satisfaction from not only reducing your electric bill as low as possible, but also know that you, your family and your pets won’t have to live in discomfort after the next Florida hurricane.