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The Great Myth of Solar Panels and Batteries

Estimated time to read: 11 minutes

When it comes to solar panels and batteries, customers often have concerns over how these panels and batteries work with each other. Do you need both solar panels and batteries or can you just have the panels? What about generators? What’s the deal when the grid goes down?

In this blog post, IES Energy Solutions Manager Justin Charles talks about one of the greatest myths in the world of solar energy – the relationship between panels and batteries.

Justin has 12 years of experience in the alternative energy space, specifically the solar industry, and runs the solar division of IES where he focuses on building commercial opportunities, particularly in regard to creative design, engineering, and helping customers with finance solutions that allow them to afford the projects they want.

Do you actually need batteries to go with a solar powered system?

One of the largest misconceptions about solar is that you need batteries to go with it. In reality, this is actually a myth. Much of it boils down to how you want to design your system.

“A lot of people think that in order to have a solar energy system, you must have batteries to connect to it. In reality, this is not true. Batteries are something that only a few customers need or want, but most solar energy systems are connected directly to the grid without any sort of storage system between them. Your energy goes right back into the grid and to the utility company, and it’s used by your home in real time. Any excess energy you produce goes to the utility company. Then, when you need more energy, it comes back in from the utility company. You’re not storing the energy you produce on site in any way.”

Why Batteries?

“Some customers will choose to add batteries to their system, and that’s a choice that happens for a couple of reasons. First, one of the biggest reasons is usually because your utility company doesn’t give you credit for energy you send back to the grid, and if they do, they give you a small amount of credit for it. Most companies work on a system called net metering. When you send the excess energy back or it comes to you, they’re giving you credit in the form of kilowatt hours. So you don’t really have to ask yourself “Did I use my energy right now, or am I using it later?” They’re just tracking how much you sent back and how much came in before reconciling it and giving you a bill for the difference.”

“You might pay the utility company 10 cents for your electricity, and they buy it back from you for two cents because that’s what they pay for electricity in some mathematical calculation that they don’t let you see. In those situations, some consumers will try to store their energy. During the middle of the day, when they’re making more than they’re using, they’ll store it up in a battery, and then in the evening or overnight when they’re not making energy and they’re pulling it in from the grid, they’ll deplete the battery to use that energy.”

“That’s one of the two reasons that people will look at a battery. The second reason is for backup needs when the grid goes down. Right now, when your normal solar energy system is connected to the grid, when the grid goes down, the solar energy turns off. You’re not producing power when the grid isn’t on. That’s a safety feature because when you have linemen and other people out working on the power grid, they’re doing it with the assumption that there’s no power there, and it’s a safety issue. It doesn’t take a lot of current at 12,000 volts to kill a person.”

There’s this inherent requirement for all PV systems that they turn off when the grid turns off, and that feature’s been there for 20 or so years now. When people who want their PV to continue to produce energy and want to have reliable energy during an outage, they add batteries. They then add a transfer switch or a disconnect just like you would have with a generator to prevent any power from going back out into the grid in those circumstances.”

This all means that batteries are an option that you can use to still have power in a safe way in the event of a power outage. Batteries are an option that allows you to have power during an outage in a safe way.

“During power outages, when you’re looking at a system like this, you need to design it very carefully. You’re looking at two calculations. You have to figure out what you want to run and how long you want to run it. The battery system has to have its own inverter, which is converting the battery energy back to usable AC energy. It also has to be able to handle everything you want to run at the same time, so it has to be a certain size. A good analogy for this is like an engine in your car. If you’re just taking two passengers, you have that small four-cylinder engine and it can work well for a couple passengers. But if you wanted to tow 10 tons of cargo in the back, that’s going to be a big problem for your four-cylinder engine.”

“You have to think about what you want to power all at once, and then you have to have the storage in kilowatt hours. That’s like the size of your gas tank. You’re taking into account questions like “Do I just want to run a couple of refrigerators, my TV, and the AC in one room so that I’m comfortable until the power comes back on?” or “Do I want my hot tub, my pool, my water heater, my sauna, and my five HVAC units in my mansion to keep running?”

“That affects how big the equipment is and how much battery storage and energy you need. Because when we’re doing things with solar, the idea is that the energy from the sun is going to regenerate and recharge those batteries. But what if this is in the middle of winter? What if there’s snow on your panels for a day? What if there are clouds and it’s not a beautiful, bright, sunshiny day? How long do you need to have certainty that this stuff is going to run in the event that there’s no energy from the sun to recharge it?”

It’s clear that batteries provide significant advantages when it comes to power outages. But how does a solar powered system with batteries compare to one equipped with a generator?

“Batteries are expensive, plain and simple. They are not a small investment. There are a lot of times that, when the customers come to us, the cost of their battery system is as much or more than the rest of the PV or solar energy system that they were looking at.”

A generator is a much lower cost way to get a long-term backup solution. You’ve got an engine and a gas tank, and that gas tank might be liquid propane or it might be natural gas, which is coming from the city, or it might be diesel. You have the ability to, for a lower cost, power a much larger quantity of equipment. The cost to generate a lot of electricity with batteries instantaneously is quite expensive, especially when the cost to do the same with a generator is not that expensive. It’s an internal combustion engine, which is reasonably cheap to produce at this point.”

“Instead of having these lithium ion batteries, your fuel is just the fossil fuel that you’re using. The negative ramification of that is that it’s not a green item. It’s a fossil fuel, you’re burning it, and there is a limit on that. So when you look at maintenance requirements, you have to service it like an engine. If you drive your car, you have to change the oil and things like that. You also have a limited fuel tank. Even if you bury a 500 or 1,000 gallon propane tank in your yard, you will eventually run out of propane. The idea behind solar and batteries is that in a really long outage situation, theoretically, the sun is going to shine every day to some capacity and recharge your batteries to some capacity, allowing you to have power.”

“It comes down to individual concerns. Is it that your power goes out for a few hours every so often? Are you worried about a 10-day outage? Sometimes the solution for people is a generator and batteries, where we size the batteries slightly smaller so that there isn’t as much expense in that. If there is a problem and the sun isn’t shining as much, the generator can kick on and recharge the batteries. If it turns into a really prolonged outage, the generator can kick on and power the rest of the house.”

“There are lots of ways to solve that, but some ways it’s a cost-benefit ratio kind of item. Generators are a lower cost solution that have a carbon-based fuel source, so you’re going to create some pollution with it. It is a limited runtime environment because you’re going to run out of power or fuel eventually. You can always get more delivered, but if you don’t have access to that in whatever the scenario you’re worried about, then you can run out of fuel.”

“The batteries are theoretically going to have an unlimited energy supply if they’re connected to your PV because it will recharge when the sun’s out. It is a green product from the standpoint that it’s not emitting carbon at that moment. However, a lot of people will talk about the pollution or carbon emissions during the creation or manufacturing of the batteries, which is honest and true. You’re not going to have a problem with the maintenance on the batteries by comparison.”

What about new products on the market like Enphase’s new IQ 8? What about sunlight-only backups?

“Enphase has a really amazing product on the market right now. Most of the solar energy systems we install are Enphase based, and it’s their new IQ 8 microinverter. What that system allows is when the grid goes down, it will still produce energy and power your home without batteries. There are pros and cons to this, and it’s a little intricate, but you still have a transfer switch like a generator or you have a battery system that disconnects you from the grid during the outage so that you don’t send power back to the grid in a dangerous manner. But whatever amount of energy you’re producing at that instant in time will be made available to your home.”

“When you think about PV production or solar energy production, it works a lot like a bell curve. As the sun is rising, you start to have this slow but gradual increase in what’s available or what you’re producing, and then you get to the middle of the day and you have most of your energy being produced. It then ramps back down as you go towards the evening until the system shuts off. So, if you’re thinking, “Hey, I’m going to get up in the morning and turn on a couple of outlets and plug in my laptop,” you might have enough energy to do that. But if you wanted to get up in the morning and have your entire HVAC system running for your home, that’s probably going to draw more power than the sun is producing at that moment in time from your PV system. It won’t allow it to turn on.”

“In fact, you’re calling for more energy than it’s producing. Not only will it prevent your HVAC system from turning on, it’s not going to allow anything to turn on because your home as a whole is asking for more than it can produce. It just turns everything off as a safety precaution because feeding less power than things need is dangerous to appliances and it can break them. Then, once you get to the point at which you’re producing enough power that it allows you to run what you’re asking it to, it will turn the system on.”

“You can also manage this manually by looking and seeing how much power you’re producing because it’s going to be connected to a cell phone app. You can, for example, look at the app and figure out something like ‘I’m producing 10 amps of power right now. Okay, I’m going to go run my microwave because that only takes five.’ You can manage yourself. Another example could be that you get to the middle of the day and look at your power production and say ‘I’ve got enough energy right now. I could run the AC for the next couple of hours and cool it down because it’s really hot.’”

You have to balance expectations with what the system can actually produce and do for you. For the people that just want to know that during a long-term outage they would be able to have control over some power in their home and do certain things, it can be a phenomenal solution for them.

If you or your business is considering switching to solar, reach out to us by going to our website, iesenergysolutions.com, or by giving us a call at (855) 447-6527.

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