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Can You Store Electricity from Solar Panels?

how long can solar panels store energy

Yes, solar energy can be stored. Solar panels are an incredible tool in combating climate change. Your solar system produces solar power with no coal or gas, no harmful CO2 emissions, and no money coming out of your pocket. The only problem is: that it only works when there is sunlight, while the peak energy demand is early in the morning and late in the evening. Effectively, solar panels produce the most power when it is needed the least – when you are at your work. 

However, solar batteries can solve this problem. As compact solar energy storage, solar batteries are the solution to renewables’ biggest issue – their intermittency. It goes without saying that solar batteries cost a lot, so exploring options you as a solar homeowner or a business owner have is necessary. Of course, larger solutions exist as well, from large-scale batteries to thermal and pumped hydro storage, capable of storing and supplying incredible amounts of power. 

How is Solar Energy Stored? 

The biggest issue with solar energy is how to store it. Current top-shelf solar batteries store over 90% less energy than their fossil fuel-based counterparts. However, with the increasing energy density of solar batteries and with the increasing efficiency of home devices, solar energy storage solutions, such as lithium-ion batteries, can store more energy and provide your home with more emergency power. 

As your solar energy system produces the most power when you need it the least, it goes without saying that you need some kind of energy storage. However, to be able to store renewable energy, it has to be converted into some other kind of energy. This energy is mostly potential energy, thermal energy, or chemical energy. Let’s see what this looks like in the real world. 

Potential energy is a form of energy that solar energy can be converted to. The simplest form of potential energy can be found in hydro-dams – the high elevation of the water column has a lot of potential energy. When you need electricity, you open the valves, and the water starts flowing. In doing so, all the potential energy is converted into kinetic energy, which then spins the turbines and generates renewable energy. This is effective solar energy storage. 

Storing solar energy can also be done in chemical form in electrochemical batteries. Indeed, you have several of these devices in your household now – they are called batteries. When exposed to current coming from solar energy (possibly generated in solar panels), chemical reactions happen in solar batteries. Once the current is removed, the solar energy stored in the battery stays there for a long time. When you connect the battery to a power user (such as a lightbulb, your fan, or laptop), the chemical reaction reverses, and the solar energy stored is released. 

The last type of solar energy storage we discuss here is thermal energy storage. Although rare, it provides a good source of power. In this case, concentrated solar energy heats up an element. The element is either a form of salt or metal. Once heated, the material melts, so it can store energy and act as battery storage. When you need power, the molten material starts heating water, which turns into steam which spins turbines and generates electricity. 

Types of Solar Energy Storage

These types of solar energy storage have found their way into our daily lives. Far from schemes on a paper or numbers in an article, these solutions are practical forms of solar energy storage that have helped us store energy and build the world as we know it. Being able to generate electricity but not postpone its use would limit the ability of every utility grid, as it would not be able to store excess electricity. Here are some commercial and residential ways that we can use to store electrical energy: 

Battery Storage

Battery storage is the most common solar energy storage there is. As solar power is generated by your solar panels, your solar panel system stores all excess energy into batteries. They are usually lithium-ion batteries, which have a good weight-to-energy-density ratio. For this reason, most solar batteries are lithium-ion batteries, from the battery in your smartphone to your Tesla PowerWall 2. 

Batteries, however, come in many different forms and types. The most common type is the lithium-ion battery for devices and domestic use. Your car ignition system is probably powered by lead-acid batteries, while other types exist as well. Gel batteries, for example, are still in the research phase but show promising results for future utility grid integration and expansion of energy capacity used to store excess renewable energy. 

Thermal Storage

When your solar panels produce electricity and your want to store energy that you cannot use right away, the simplest energy storage system is thermal storage. Simply running excess electrical power through a resistor or a heating body of any kind will generate tremendous amounts of heat. Just 1 kWh of electrical energy is enough to boil 10 liters or 2.65 gallons of water. 

With this in mind, thermal storage solar batteries were developed. This type of battery can run current through a material, usually metal or salt, and melt it. Alternatively, other types of medium, such as gravel, can be heated to high temperatures and used as a thermal mass to store energy. When the energy is needed, water or air is run through the molten medium. As the heat expands the air, it spins turbines and produces electricity that is so much needed. 

Alternatively, solar power can be sent to thermal storage in other ways as well. Concentrated solar is a great example where solar power is not converted to electricity by means of solar cells. Rather, mirrors are used to concentrate sunlight and melt a medium, similarly to molten metal batteries. This storage exists worldwide, but issues with the medium solidifying (such as molten salt) during particularly cold and cloudy periods limit the use of this battery technology. 

As the renewable market expands and the need to have the electricity stored increases, many innovative ways have been found to increase storage capacity while at the same time reducing the pressure on the electric grid, reducing your power bills and your carbon emissions. A UK-based company has come up with an idea of a smart water heater

The water heater uses excess solar energy produced during midday (when it is not used) to heat water, which can, later on, be used for a variety of uses – from heating space to providing running hot water for your household. This form of solar energy storage is also called energy use dispersion and is meant to reduce peak energy use. In turn, the electrical grid gets more stable without you losing life comfort. 

Mechanical Storage

As lithium-ions are expensive, and the need to store excess solar production is ever increasing, the need for a cheap battery pack, which would not rely on fossil fuels, has also increased. Having a lot of solar plus storage would also mean that the peak demand would be easier to satisfy and that fewer peak power plants would need to be kept operational. Here are a few of these storage solutions: 


Flywheel as energy storage is a great and a very old idea. Flywheels are basically wheels, usually very heavy, made of different metals which can absorb a lot of kinetic power. When there is a surplus of solar energy, every kilowatt-hour of it can be stored in a flywheel by having an electric motor spin the wheel. Once there is no surplus of power, the wheel keeps spinning as it is very aerodynamic and faces little resistance. Once peak hours arrive, the electric motor is reattached to the wheel, where the spinning motion of the rotor now acts as a power generator. 

Pumped Hydro

Pumped hydro is another form of mechanical storage. Relying on the potential energy of water, pumped hydro consists of two water bodies placed at different altitudes. The upper water body is a lake, either natural or man-made, while the lower one can be a river or another lake. When there is excess solar energy to be stored, powerful pumps pump water uphill: from the lower lake to the upper. 

Once there is peak demand, the water from the upper lake is simply released over turbines, just as it would be in a regular pool. This way, the pumped hydro, or a reversible hydro plant, acts as a solar-powered battery back. The biggest pro of this approach is the high capacity and the ability to provide power in an instant, while it may be geographically and cost-prohibitive, especially in low-lying countries. 

Compressed Air

Compressed air is yet another solution for storing excess energy on a sunny day. Cost-effective and environmentally friendly compressed air energy storage systems can be used on existing sites, especially in places of old, phased-out coal and salt mines. In the process, excess energy is pulled from the grid. It powers huge air compressors, which compress the air and send it underground. When energy is needed, the compressed air is sent into an expander, which powers the turbine. 

Cost of Solar Energy Storage

Solar energy storage does not come cheap. If you want to store solar energy, you will need to cash out between $9,000-12,000. This money should cover a basic solar battery with around 10 kWh of storage capacity. Bigger models will cost more, but the good thing is that renewable energy batteries are scalable, and their price keeps falling year after year. To better estimate how much energy you need to store, check out your monthly power bill or schedule a meeting with an energy specialist. 

Benefits of Storing Solar Energy

As solar energy is highly intermittent, without good solar energy storage, we cannot rely on solar panels to usher in a clean energy era. A solar-powered battery pack costs a lot of money but can provide energy as backup power, improve energy independence, enable you to save on your electric bill (depending on how much energy you consume), and it can even reduce your carbon footprint. Good solar energy storage will also be there during power outages and will provide power even when there is none in the network. 

Backup Power

As a source of backup power, small residential battery packs (usually around 10 kWh of stored capacity, which can be scaled up) are usually enough for a single-family and their energy needs for a portion of the day. However, these solar power packs are usually costly and can require specialized teams to install them in a safe way. Furthermore, as they demand special conditions to be stored in, they can also decrease the amount of available space you have. 

On the other hand, installing a solar battery in your household can provide multiple benefits, especially during power outages, blackouts, or brownouts. There will be no interruption during maintenance works on the grid, and you can rest assured that all your devices and appliances will be able to push through with your needs. Most solar installers can install a battery as well. 

Energy Independence

A good solar battery, combined with solar panels, also means energy independence. Your solar installation, with a solar battery, can provide power to off-grid properties, boosting your independence and ensuring that no nights are spent in darkness. When designing your solar system, you should plan to install batteries right away, as modifications to the system, later on, can cost more than an installation anew. 

Savings on Electric Bill

Your solar battery can also help save on your electric bill. Some countries have a variable-rate electric system, which increases the price of energy during peak hours. Having solar storage can easily help you overcome this issue by storing energy for later use. Peak demand in most households is around dinner time, so 5 PM to 9 PM. You can contact your power provider to see whether you pay more or not. 

Carbon Footprint Reduction

As not all power that is generated by your solar panels can be used right away, it is important to be able to store it. When storing energy for later use, you are effectively removing some fossil-fuels-based electricity from your energy use portfolio. This means that you can enjoy the benefits of solar energy even long after the sun has set. 

Solar Battery vs Power Generator

When thinking about storing excess energy, especially for blackouts, many think that their investment in a solar battery is too expensive and decide to go with a power generator. However, in the long run, a solar battery is much cheaper, especially considering the environmental benefits. Here is a quick comparison between a solar battery and a generator. 

FactorSolar Battery Power Generator 
Max Power Output21 kW10 kW
Max Storage CapacityUp to 40 kWhDepends on gas availability
Can Power an Entire HomePossible but usually noYes
Instant Response in a Blackout YesNo, has to be manually started
Produces GHG in operationNoYes
Noise LevelNext to noneVery noisy
Power Supply Time24 Hours + with bigger modelsDepends on gas availability
Annual Maintenance None, a simple inspection is enoughYes, oil and filters have to be replaced annually 
Warranty Yes, up to 10 yearsYes, up to 2 years
Cost After 10 Years$9,000 - $16,000~$19,000


How do you store off grid electricity?

You can store off-grid electricity in batteries. Solar and wind batteries are the best way to store excess power as they are instantly available, do not take time to build up their power output, and are readily available to be charged even during days of partially overcast skies. These batteries come in many forms, with lithium-ion batteries and lead-acid batteries being the most common types. 

Can you use solar without batteries?

Yes, you can use solar without batteries. To do that, you need a smart meter and net metering policies in place. Net metering enables you to use the grid as a form of energy storage and effectively substitutes for a battery. 

How long will a 10kw battery last?

Depending on how much energy you consume, a 10 kW battery can last for around 8 hours for a typical American household. As an average American home consumes around 30 kWh of energy every single day, a 10 kWh battery will hold enough energy to supply such a home with power for around a third of a day. You can significantly increase this time by reducing energy use: no heating or cooling of any kind for as long as the power is out will result in around 24-hour storage capacity in the same battery size. 

Do solar panels work without sun?

Solar panels can produce some energy on cloudy days or when there are a few passing clouds. Your solar panel system will also produce some power during nights with a full moon. In both cases, however, the amount of power produced is minimal, especially in comparison with direct sunshine power output. 


As the interest in solar energy increases, so does the need to store energy produced by solar arrays. Solar energy storage solutions are multiple and of different kinds, but the high cost is sometimes prohibitive, especially for developing countries. However, as the technology keeps expanding and getting cheaper, we are likely to experience more solar energy storage deployed. 

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