When you install a home battery, you’re gaining a backup energy reserve in the case of an outage.
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Whether you have a solar panel system at your home or not, a home battery can be used to store electricity and deliver it to your home appliances and devices. The benefits of a home battery are clear, especially during short or long-term outages, and in areas with Time-of-Use (TOU) rates or weak net metering policies. In this article, we’ll show you how to calculate how a solar and battery system can power your house during a grid outage, and give you some tips for maximizing your battery usage. Compare bindings quotes for solar and battery systems to backup your home. Without running AC or electric heat, a 10 kWh battery alone can power the critical electrical systems in an average house for at least 24 hours, and longer with careful budgeting. When paired with solar panels, battery storage can power more electrical systems and provide backup electricity for even longer. In fact, a recent study by the Lawrence Berkeley National Laboratory found that when heating and cooling are excluded: “(A) small PVESS with just 10 kWh of storage (at the lower end of sizes currently observed in the market) can fully meet backup needs over a 3-day outage in virtually all U.S. counties and any month of the year.” PVESS stands for photovoltaics and energy storage systems. But exactly how long you can power your home with solar battery storage varies for each home and depends on three main things: We’ll show you how to budget your electricity to meet your solar and battery capacity below. First, let’s start with identifying your battery storage capacity. Home battery capacity Capacity — the amount of energy a battery can store — is one of the main features that influence how long a battery can power a house during a power outage. Battery capacity is measured in kilowatt-hours (kWh) and can vary from as little as 1 kWh to 18 kWh. Multiple batteries can be combined together to add even more capacity, but a 10 kWh home battery is typical for most homes. Related reading: What Size Solar Battery Do I Need? During a power outage, assuming you have a fully charged home battery, you will be able to use most of the 10 kWh of stored energy. However, depending on the battery type, you’ll want to leave a minimum charge of 5-10% on your battery for a couple main reasons: To start your solar inverters in the morning so you can recharge your battery with solar power For a 10 kWh battery, you’ll want to leave at least 1 kWh of capacity in reserve at all times. That leaves you with 9 kWh of battery capacity to power your home during a grid outage. Related reading: The 8 Best Solar Batteries (and How to Choose the Right One For You) The beauty of pairing battery storage with solar is that you essentially create your own miniature utility to power your home. This is especially useful during prolonged power outages because unless you have battery storage, your solar system will be turned off by the local utility to prevent the backflow of electricity from injuring workers trying to repair the grid. But if you have battery storage, your system can operate independently when the grid is down. This is called “islanding.” Solar panel systems are measured in kilowatts (kW) which represent the amount of energy the system can produce in an hour of peak sunlight. So a 5 kW solar system can produce 5 kWh of electricity per hour in ideal conditions. However, since conditions aren’t always ideal, we typically assume a performance ratio of 75%. The average number of peak sunlight hours per day varies from 3.5 to 5.5 in the US. Multiply the system capacity by sunlight hours and 0.75 to find the daily output of a solar system. For example, here’s how you would find the daily output of a 5 kW solar system getting 4.5 peak sunlight hours per day equals: 5 kW solar system x 4.5 sunlight hours per day x 0.75 performance rating = 16.875 kWh per day In many cases, that’s more than enough to power essential electrical systems and recharge a 10 kW battery to use overnight. But electricity needs vary from home to home, so let’s run through some common appliances and how much energy they use. Your electricity needs during a power outage How long solar battery storage can run your home depends on how much electricity you use. And how much electricity you use depends on which appliances and systems you’re running. During a power outage, it’s recommended to budget electricity for the most necessary things first and then make a plan for the remainder of the capacity. For many homeowners, the list of priorities includes: It’s worth noting that heating and cooling take a ton of energy, and typically aren’t configured to be powered by critical battery backup systems. Whole home backup is possible, but it takes a large solar system with around 30 kWh of battery storage. Let’s run through an example scenario of powering essential systems during a 24-hour power outage to get an idea of how much solar and battery capacity you’ll need. Use the tables below as an a la carte menu to create your own battery storage budget. A refrigerator is among the most important things to power during an outage so that you can avoid having your food and drink go to waste. If you have a modern, ENERGY STAR-approved model, your refrigerator is using around 1-2 kWh of electricity a day. If your fridge lived through Y2K, you might be looking at closer to 5 kWh per day. Refrigerator electricity usage can be minimized by opening the door less and raising the temperature slightly. If you are preparing for a planned Public Safety Power Shutoff (PSPS), set the temperature very low before the shutoff event, and then set it to a higher temperature once the grid power goes out. That way the fridge starts cold and you can devote less battery capacity to power it during the outage. Let’s say you have a relatively modern ENERGY STAR-certified fridge that uses 1.5 kWh per day. Running total: 1.5 kWh 0.12 kWh per brew / 0.4 kWh per hour on warmer Even during a power outage, people gotta eat. And in a large enough outage, it may not be practical to eat out or order delivery. Let’s say you make a pot of coffee and toast in the morning (0.2 kWh), microwave some leftovers for lunch (.12 kWh), and bake a frozen pizza for dinner (0.75 kWh) because you’re trying to clear out the freezer. That amounts to just over 1 kWh throughout the day. Running total: 2.5 kWh Water heating accounts for an average of 18% of the total energy used in the household, or around 162 kWh per month. On a normal day, a water heater runs for around 2 to 3 hours a day, which means that it will consume roughly 4-5 kWh of electricity a day. Heat pump water heaters are more efficient and can run on around 2.5 kWh per day. But power outages are not normal days. To save electricity, you may want to skip or shorten your shower, wash your hands and rise your dishes with cold water, and hold off on laundry for a day or two. And if you have a gas-powered water heater, water heating is a non-issue in terms of battery use. But for the sake of argument, let’s say you put on some extra deodorant and limit your water heating use to 2.5 kWh per day. Running total: 5 kWh Compared to larger appliances, lights require very little electricity, especially if you have compact fluorescent (CFL) or LED bulbs. Even at the high end, a 38W LED bulb or 150 W incandescent bulb uses just 0.038 kWh per hour. If you want to learn more, please visit our website GECONA SOLAR. So if you budget 1 kWh of battery storage per day for lighting, you could run 26 bulbs for 1 hour each — more than enough to provide light for trips to the bathroom, closet, and getting ready for bed. Running total: 6 kWh Let’s be honest, one of the worst parts of power outages is going without internet and TV. Sure, you try to read a book for an hour or two, but that familiar glow is calling your name. To keep the WiFi on, you’ll need about 0.024 kWh. If you work from home, you can run your laptop for 8 hours for another 0.4 kWh. And if you want to wind-down with a movie or 3-hour Netflix binge, you’ll need another 0.54 kWh. That adds up to 1.18 kWh, but we’ll round up to 2 kWh to account for phone charging and multiple devices running at once. Running total: 8 kWh As you can see from the table, heating and cooling take a lot of electricity. So if you only had a 10 kWh battery you’d have maybe 2 kWh to budget for running fans or space heaters — which wouldn’t last very long at all. To power heating and cooling for a substantial period of time, you typically need two or three batteries that add up to 30-40 kWh of backup capacity. Another thing to consider is powering medical equipment during a power outage. Certain equipment, like a nebulizer, requires a significant amount of electricity and could eat through 10kWh of battery very quickly. Is getting a solar battery worth it? Weather-related power outages in the US increased roughly 78% from 2011 to 2021, and are becoming a reality for more homeowners. If you like clean, quiet, and hands-free backup energy that can power your home for several days during outages, then solar and battery are totally worth it. Not only can a battery keep your home powered, it can keep your local grid running, as we saw in California in September 2022. And, of course, there are the local and global impacts of reducing fossil fuels that pollute the air and contribute to climate change. Compare bindings quotes for solar and battery systems to backup your home.How long can a solar battery power a house?
Solar system output
How much electricity does a solar system produce?
Refrigerator: 1.5 kWh per day
Model
Energy use
Older 15-cubic foot unit (1996)
5 kWh per day
Newer ENERGY STAR 17-cubic foot unit
1.16 kWh per day
Kitchen and cooking: 1 kWh per day
Appliance
Energy use
Electric oven
2.3 kWh per hour
Oven: surface
1 -1.5 kWh per hour
Microwave oven
0.12 kWh per 5 minutes
Coffee maker
Electric water heating: 2.5 kWh a day
Appliance
Energy use
Electric water heater
4-5 kWh per day (running 2-3 hours)
Heat pump water heater (50-75 gallon)
~2.5 kWh per day
Lights: 1 kWh per day
Bulb type
Energy use
CFL/LED (8 W) equivalent to 25 W incandescent
0.008 kWh per hour
CFL/LED (15 W) equivalent to 60 W incandescent
0.015 kWh per hour
CFL/LED (27 W) equivalent to 100 W incandescent
0.027 kWh per hour
CFL/LED (38 W) equivalent to 150 W incandescent
0.038 kWh per hour
TV and device charging: 2 kWh
Device
Energy use
WiFi router
0.024 kWh per day
Modern TV: LED/OLED 4k or 1080P HDTV (20″ to 70″+)
0.014 to 0.18 kWh per hour
TV: Plasma (40″ to 50″+)
0.4 to 0.48 kWh per hour
Desktop computer
0.06 kWh per hour
Laptop computer
0.02-0.05 kWh per hour
Tablet
0.032 kWh per day
Air Heating and Cooling: Variable
Appliance
Energy use
Heating
Electric furnace (with fan)
10.5 kWh per hour
Portable heater
1.5 kWh per hour
Baseboard heater (6-foot unit)
1.5 kWh per hour
Cooling
Window/Wall AC (8k to 18k BTU)
0.73 to 1.8 kWh per hour
Central AC (3 ton – 12 SEER)
3.0 kWh per hour
Pedestal fan
0.03 kWh per hour
Ceiling fan
0.025-0.075 kWh per hour
Medical equipment
Device
Energy use
Nebulizer
1 kWh per hour
Oxygen concentrator
0.46 kWh per hour
Sleep apnea machine (CPAP)
0.2 kWh per hour
In several places worldwide, solar has single-handedly powered entire communities. Therefore, yes, you can definitely run your house on solar power alone. It is the most flexible power source the world has ever seen – powering everything from pocket calculators to entire cities.
And when you consider the fact that every hour enough sunlight strikes the Earth to power the world’s population for a full year, it becomes obvious that a single house can be powered with solar. The more important question, however, is “how can I run my house on solar power only?”. Let’s find out the answer to that.
The first and probably the most important thing you will need to power your entire house with solar is proper system size. Having fewer than the required panels and your house won’t have enough power, and having more than the required size means you would be unnecessarily spending more money.
The system size is calculated through a system design. A system design takes into account your historical energy consumption and calculates the number of solar panels you will need.
You can use a solar calculator for a rough estimate of the number of solar panels you may need. This will also give you an idea about the potential savings your system will generate. Once you decide to go ahead with the preliminary system size, you can approach a reliable solar expert for a detailed, more precise system design.
However, knowing the number of solar panels is just one part of the equation. Powering your home 24 x 7 with them needs some other considerations too. Let’s take a look.
The biggest limitation of solar power is that it is available only during the day. The typical power consumption of a home, on the other hand, peaks during the evenings. This mismatch means no matter how many solar panels you use, they will be of no use after sunset – unless you choose one of the following two solutions:
Net-metering allows you to send the excess energy from your solar panels into the grid during sunny hours, and use some energy from the grid during darker hours.
Ultimately, you will be billed only if you take more energy from the grid than you give it. If your system is accurately designed, usually net-metering can result in zero or near-zero electricity bills.
Sending electricity back to the grid is like handing it over to someone to safe keep for a while. But what if you do not have anyone to babysit your excess electricity? The most common way to store energy is by using batteries.
Batteries are chemical devices that undergo a chemical reaction when charging, and when you need energy, they undergo a reverse chemical reaction that generates almost the same amount of energy you used for the first reaction. Isn’t that cool?
Both net-metering and batteries have their own pros and cons. Net-metering saves the cost of batteries, which can be a significant amount. Batteries, on the other hand, ensure energy security when the grid itself is not reliable, or worse, absent from your location.
Therefore, batteries are a favorite for remote, off-grid cabins and even in places where blackouts are common. But technology keeps evolving, and you don’t necessarily have to choose between net-metering and batteries. With the advent of better hardware and even better software, you can have system configurations wherein you can enjoy the benefits of both.
Let’s go over the types of system configurations, and how effectively they help you run your house on solar power alone.
The most basic configuration is having grid-connected solar panels with net-metering. This allows using some solar power during the day, sending some of it back to the grid, and then using power as needed from the grid when the panels aren’t generating anything. Although simple and useful, this configuration has a couple of flaws.
Firstly, in the event of a blackout, you cannot use power from your panels, even during sunny hours. Regulations in most places do not allow solar power systems to operate when the grid is down (also known as islanding protection), to protect any technicians from solar power flowing back into the grid.
Secondly, this option is not useful if you have no grid connection, or have an unreliable grid.
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Enphase, the giant in microinverters recently coined the term “sunlight backup”, which means backing up your appliances with solar power when your grid shuts down. This is a solution to islanding protection.
This option makes use of technology that severs the connection between a solar power system and the grid while keeping the connection between your solar panels and some key appliances intact. You may not power heavier appliances like ACs, but you can keep powering your phones, lights, fridge, etc. as long as the sun shines.
The home essentials backup option differs from sunlight backup in the fact that it is not restricted by “sunlight” hours. In this case, you can power several appliances during the day as well as the night.
This option makes use of a battery bank, and also allows you to connect an AC generator (such as a gas generator) that turns on seamlessly when grid power goes down. This way, you can power any and every device, grid or no grid.
Through the use of intelligent software, this option also allows you to manage which appliances you want to operate. Because let’s face it, running an AC on a generator is not a wise thing to do, unless you own an oil well.
The home essentials backup option also allows you to transmit metered energy into the grid and earn money from it, given that such programs exist in your location.
The last, and ultimate system configuration is full energy independence, which, as the name suggests, does not need grid support at all. With sufficient solar panels, a full-fledged battery bank, and possibly an AC generator, your system is capable of powering through the worst and longest of blackouts, and even without a grid at all.
Such a system offers all the benefits of the previous three configurations and goes beyond that. This configuration is the most expensive among all four, but it also saves the highest amount of money over its lifespan – which is a whopping three decades or more.
Here’s a table that gives an overview of all four system configurations:
The size of a solar power system needed to power your whole house depends on your consumption, your home’s location, and its orientation. However, on average, most homes need anywhere between 5 kW and 10 kW to power everything inside.
As mentioned in the previous answer, anywhere between 5 and 10 kW is needed to power a whole house. In terms of the number of solar panels, roughly three panels make a kW, so 15-30 solar panels are needed to power a house.
As long as you have clear sunlight falling on a correctly designed solar power system, your house can run continuously on solar panels. However, if the weather is overcast, your system may generate less power. Also, if your consumption increases say by adding in a new electric vehicle, then the available solar panels may not be sufficient.
Solar power is a magnificent source of energy. The sun powers everything on our planet, and it can definitely power a single house. To do that, you only need to ensure you have a correctly sized and properly installed system.
The intermittency of solar did not allow homes to be powered effectively and efficiently through nights or darker days in the past. However, with modern batteries and smart technologies, customers can choose from several types of backup systems that ensure that a part or the whole house can run on solar power alone.
Ultimately, it is your choice how you want to power your appliances, and how much reliance you want on the grid and solar power. Whatever option you choose, either way, choosing solar is a win in itself!
If you want to learn more, please visit our website All In One Solar Power System.