You and your family are enjoying dinner together when the power suddenly goes out. No one bats an eye because your home battery storage system kicked in so fast that the lights didn’t even flicker. After dinner, your kids crank up the air conditioner and watch TV as you run the dishwasher and throw a load of laundry into the washing machine.What’s wrong with this picture?
The primary reason that homeowners buy home battery systems is to provide backup power when the grid power goes down. It’s easy to assume that you should size your home battery to match the amount of energy your home usually consumes.
In reality, home battery systems are typically not sized to meet all of a home’s normal electricity needs for an extended duration. In fact, they can provide better and more prolonged backup support when you size your storage system to meet just your home’s essential energy needs.
Only in very specific circumstances does it make sense to use a battery for whole home backup. Below, we break down when a battery is best for “partial home backup” versus “whole home backup,” so that you can size your home storage system most effectively.Partial home backup: best for short-term blackout support
If you are looking for reliable backup power during a temporary grid outage, it is more efficient and economical to size your battery to power only your most essential devices: lighting, internet, central heating, and water pumps. You may not need to back up your entire house.
The average U.S. household has an energy demand of about 30 kilowatt-hours (kWh) per day, but much of that demand comes from powering big appliances – like dishwashers and washing machines – that you can live without for a day or two. Plus, just turning on those power-hungry appliances requires up to eight times more power than they need while running. This makes it even more important to optimize your energy use during a blackout, to prolong the amount of time that you have for backup power while waiting for the grid to come back on. Some larger appliances are therefore considered less-essential, at least for a short period of time. Examples of these appliances are listed in the table below.
Common household appliances for backup
|Essential appliances||Less-essential appliances|
Not to worry, if you do need to turn on your air conditioner during a blackout, smart features like Power Start™ can help you mitigate power surge demands. You can also work with your installer to configure your backup electrical panel so that when the power goes out, your essential appliances can be powered.Whole home backup: best for powering all home devices or off-grid mode
If your goal is to operate all your electrical appliances and power your entire home during grid outages, it may make sense to match all your home’s power and energy consumption with backup power. Off-grid simply means that your home can function when the utility power grid is down. Power can come from a combination of energy storage, solar, and sometimes a traditional generator to create a microgrid that can operate independently of the grid, sometimes in perpetuity.
You could even complement a solar plus storage system with the use of a traditional generator for extreme situations when an extra boost is needed. For these situations when you need extra piece of mind, the Enpower™ smart switch includes integrated generator support.So, should I choose whole home or partial home backup?
Whether your home is a grid-connected suburban house or an off-grid cabin in the woods, sizing your battery begins with understanding your home’s power requirement and energy usage (and energy production, if you have solar).
Our System Estimator Tool makes it easy for you to understand your electricity needs and size your all-in-one solar plus storage system appropriately. Plus, Enphase installers can work with you to figure out a system that meets your energy goals.