How long can a home battery last during a power outage?

The length of time a home battery can provide power during an outage depends on the features of the battery. Some batteries, for example, have a higher wattage than others, meaning they can provide more power for a longer period. Additionally, the size of the battery also impacts how long it can provide power. Larger batteries can store more energy and provide power for a longer period than smaller batteries.

So, how long can a home battery provide power during an outage? The answer to this question depends on the features of the battery, including its wattage and size. Some batteries can provide power for a longer period than others.

Factors affecting how much of your home a battery can power

When determining how much of your home’s power you can derive from a battery, there are two main components to consider:

  • the amount of power required
  • and power supplied by the battery.

Power is calculated in either kilowatt (kW) or amps (A).

Amps vs. kilowatts: what's the difference?

The voltage is the electrical pressure, and it’s measured in volts, which is volts divided by 1000. Don’t worry, we’re not going to boring you with technical information; all we want to ensure is that if you’re more familiar with amps or kilowatts than voltages, you’ll understand! A current measure is referred to as an ampere (abbreviated amp). Power is measured in watts (W). To convert amps to watts, multiply by voltage. The United States has two types of electrical panels: 120 V and 240 V. To change watts to amps, divide the number of watts by 1,000 (and then divide by 1,000 to get kilowatts): at 120 Volts, 2,400 Watts or 2.4 kW of power are produced when 20 amps flow through the circuit. Isn’t that simple?

Appliances/circuits you want to back up.

A home’s electrical panel usually has a 200 amp capacity. This means that if you wanted to back up the whole electrical panel and simultaneously provide power to every circuit, you would need a lot of power.

But, most homes don’t need to run every appliance or circuit simultaneously. This means you (or your installer) will need to compute the power consumption of various equipment in your home or circuits on your electrical panel. Batteries are rated in terms of power in kW and current in amps.

To find the wattage of each individual appliance, you can use the US Department of Energy’s appliance load calculator. Once you have the wattage for each appliance, you can calculate the power requirement backing up your home. For example, a refrigerator requires 200 watts, 20 watts per light bulb, 25 watts for a phone charger, and 300 watts for a TV.

You can determine how much power you need based on which appliances/circuits you want to back up.

The capacity of your battery (instantaneous and continuous)

The power rating of your battery is determined by its instantaneous and continuous power. Instantaneous power is the amount of power the battery can provide in a short burst, while continuous power is the amount it can provide steadily over time.

Look at the quick power rating for appliances that require a lot of power when first turned on. This will inform you whether or not the battery can give the extra surge of power required. The continuous power rating should be used to establish how many different appliances and circuits you can power at the same time for hours on end.

You can size an energy storage system appropriately once you know the power requirements of the part or all of your home that you want to back up. The majority of batteries have a continuous power rating of 5 to 8 kilowatts. This implies they may power numerous circuits or a few appliances at the same time.

Factors influencing how long a battery can power your home

The primary factors that impact how long your home’s battery can power appliances are the usable storage capacity and the systems you use. Solar pairing and load management also play a role in shortening or lengthening the time your power supply will last.

Usable storage capacity of your battery

From a storage standpoint, you’ll first want to know how much usable capacity your battery has. This is typically measured in kilowatt-hours (kWh), which refers to the amount of power (kW) over a certain amount of time (hrs).

For instance, if your battery has a useful capacity of 10 kWh, you may utilize 5 kW for 2 hours or 1 kW for 10 hours. As with your phone or computer, your battery will lose its charge faster the more you use it.

So if you’re looking at different storage options, compare the usable capacity in kWh between each option. This way, you can make the best decision for your needs.

What appliances are you using and how long have you been using them?

The next step is to identify which appliances you’ll require and for how long, based on the number of usable capacity your battery has as well as the power consumption of your devices. You may run a 10 kWh battery for approximately 10 hours if it contains a usable capacity of 10 kWh.

  • For less than 3 hours, a 3,500 W air source heat pump;
  • 300 W TV for 33 hours;
  • 50 hours in a 200 W refrigerator
  • For 100 hours, use five 20-watt light bulbs.
  • For 400 hours, a 25 W phone charger;
  • For 1,600 hours, use a 6 W WiFi router.

If you plan to keep your essentials–phones, computers, WiFi, refrigerator and some lights–during a power outage, you’ll need a 10kWh battery to make it through nearly 24 hours. Remember that running multiple appliances simultaneously impacts how long the backup will last.

Whether your battery is paired with solar

Because a standalone battery is not rechargeable without an electricity grid, it is only a viable option for short outages. If longer outages are experienced, pairing a battery with a solar panel system is best. This way, backup power can be provided to your home indefinitely as long as the sun continues to rise.

A battery connected to a solar panel system is useful since it allows you to recharge your battery while still keeping your home powered if the rest of your block is still dark. You can provide backup power for your property even if there are gloomy days as long as the sun shines at some point.

How to load management devices can prolong your stored energy capacity

If you install a battery for your home’s backup power, you’ll need to decide which outlets, rooms, and appliances you want to include in the backup. This could be a problem if you didn’t realize an outage and tried turning on too many things simultaneously.

By installing your battery with a load management device, like an energy management system, you can let the software manage your battery usage efficiently and safely. This way, you don’t need to worry about critical load panels or battery overload. Everything will be handled by the system. This is a much more convenient solution that can prolong the life of your stored energy capacity.

In conclusion, load management devices are a great way to prolong your stored energy capacity and make life more convenient. These devices don’t have to worry about critical load panels or battery overload. Everything will be taken care of by the system.

How to figure out how much of your house you can power with a battery and for how long

To determine how much of your home can be powered by a battery, consider the battery’s power rating as well as the wattage of the appliances you’re using. A 5 kW battery can usually power many devices at once, such as a refrigerator (800 W to start, 200 W to run), furnace fan for gas heat (600 W), cell phone chargers (25 W each), a WiFi router (6 W), a dozen light bulbs (21 W per light bulb, or around 250 W total), and even a microwave.

The battery’s life is determined by how much power each item consumes and how long you use them. Appliances like air conditioners and heat pumps typically used for longer periods can use up a lot of power. A common air conditioner might consume 5 kW of power, whereas a more efficient air source heat pump may require as little as 3 kW to heat and cool your home.

It’s important to keep in mind how long you plan to use each appliance, as the longer they’re running, the less amount of stored energy you’ll have to power other appliances. If you keep your TV on daily, it will use over 7 kWh of electricity daily, a significant portion of many batteries’ typical 10 kWh of usable energy storage.

Always compare battery life when choosing between different options- use an app from your inverter or smart electrical panel to give you approximate numbers. Doing this allows you to find the best possible option for yourself and your needs rather than assuming all batteries are created equal.

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