Imagine you’re enjoying family time on a summer’s eve when the power goes out. Right about then, you immediately start to think about what you wish you could back up with a battery. Correct expectations will help set up the best ownership experience for home storage, especially the first time you use your home battery.
The power your house can run on a home battery storage for any given period will depend on several factors, such as the battery type, battery size, the amount of power drawn by the appliances currently connected to the home battery, and the size of the house. But the primary aspects to consider are how much power you need and how much power your battery can provide.
How much power do you need?
You must know which appliances (or circuits) you intend to back up to calculate your required electricity. In the US, 200 amp electrical panels are found in many residences. You would need a lot of electricity to power up every circuit simultaneously while backing up the entire electrical panel. But as you’ll discover in the section after this, batteries often deliver much less power.
Batteries give power ratings in kW and current ratings in amps. By finding the wattage of each appliance, you can calculate the power needed for backing up your home: 250 watts for a refrigerator, 10 watts per light bulb, 5 watts for a phone charger, 150 watts for a TV, and so on.
How much power can your battery provide?
Once you’ve determined how much power you’ll require to power a portion or all of your home, you can choose the size of an energy storage system appropriately. The most essential power metrics to consider are instantaneous and continuous power.
Instantaneous power determines whether or not you can provide an additional surge of energy to appliances that require it. For instance, a good pump or sump pump may use a lot of energy when you initially turn them on, but its energy needs will decrease throughout its operation. A Tesla Powerwall 2 with 13.5kWh of storage capacity can sustain 6.4kW peak or instantaneous power. The Enphase IQ Battery 10T has a peak surge power of 5.76VA (kilo-volt-ampere) while the PowerPod 2 has 5.76kVA. Look closely at this specification if your appliance requires a power spike when you initially turn it on.
Continuous power is the amount of energy (in kilowatts) your home battery storage can provide. This metric determines how many different appliances and circuits you can power simultaneously for hours. Most batteries have a constant power rating of 5 to 8 kilowatts, which means they can power several circuits or a few appliances simultaneously.
Factors that influence how long a battery can power your home
The primary factors to consider when determining how long batteries can power your home are your battery’s usable storage capacity and which appliances you’re using. However, it is also essential to consider whether your home battery storage is paired with solar and whether you are incorporating any load management systems in addition to your storage system.
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Your battery’s usable storage capacity
The first thing to consider is how much power your battery stores. Look for usable storage capacity when reviewing spec sheets or your storage quote. Usable storage capacity is measured in kilowatt-hours (kWh) because it represents the use of a specific amount of electricity (kW) over a particular period (hours).
If your battery has a usable storage capacity of 10 kWh, you can use 5 kW of power for 2 hours or 1 kW for 10 hours. As with your phone or laptop, your battery will lose charge faster as you use the device more frequently.
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Which appliances are you using, and how long you use them?
When you know how much usable capacity your home battery storage has and how much power your appliances consume, the next step is to decide which appliances you want to use and for how long. If your battery has a usable capacity of 10 kWh, you can power the following devices:
For less than 3 hours, a 3,500 W air source heat pump;
33 hours of 300 W TV;
50 hours in a 200 W refrigerator;
For 100 hours, use five 20-watt light bulbs.
For 400 hours, a 25 W phone charger;
A 6 W WiFi router for 1,600 hours.
Because you’ll likely be running multiple appliances simultaneously, the backup calculation will be much more dynamic, with many tradeoffs. For example, if you watch TV for two hours, you can only run your refrigerator for three hours. However, if you plan to keep the essentials running during an outage, a 10 kWh battery should last nearly 24 hours.
A monitoring system like the Emporia Smart Monitoring device will allow you to monitor and control how much power your appliances consume. It is designed to give users insight into their energy usage and help them better manage it. The device can be connected to solar and traditional power sources and measure energy production and consumption in real-time. It also provides advanced features, such as load shedding, time of use monitoring, peak demand notifications, and more.
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Are you charging your battery with solar?
If you install a standalone battery, you cannot recharge it until the grid service is restored.
When solar and storage are combined, you can provide backup power to your home as long as the sun rises. Even if you have cloudy days, when the sun shines, you can recharge your battery and keep your home powered.
How load management devices can help you extend the life of your stored energy capacity
Due to battery limits, most storage installations include a critical load panel and a secondary electrical panel with fewer circuits that a home battery storage can power during an outage.
The theory is that if you didn’t know there was a power outage and tried to turn on your air conditioner and washing machine simultaneously, you could overload the battery capacity and not be able to turn on what you want to operate.
When the home battery is installed, you’ll designate rooms, outlets, and appliances you want your battery to back up. And that would be for the lifetime of the battery.
However, combine your home battery with a load management device, such as an energy management system from Enphase and others. You can allow the software system to run your battery efficiently and safely. There’s no need for critical load panels anymore: you can keep nearly every circuit powered by the battery because an energy management system can perform the same function as critical load panels. It can monitor and control power to prevent overloading, provide remote access to the system, display current and past consumption, and make it easier to identify usage trends.
Want to partner your battery with solar?
If you think going solar with a home battery is the best choice for your home, DroneQuote will help you determine if it does. DroneQuote will assess if installing solar panels and backing them up with batteries in your home is worth the investment. As your solar fiduciary, the company will provide honest answers to anything solar. To get you started, DroneQuote’s consumer guide will help you determine which questions to ask your solar installers. Contact us by clicking the link here.