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A Tesla Powerwall can absolutely power a home. But there are a few things you should know about before installing this home battery:
Home Energy Requirements
Understanding what your energy requirements are is the same thing you’d need to know if you were installing a solar power system.
If you don’t have an energy monitoring set up in your home, then you can look at your electric bill. Just look at the kWh (kilowatt-hours) used each month to see how much electricity you use on average and divide that number by how many days in the month to see how many kWh you roughly use on a daily basis.
Or, you can create a list of the major appliances you use in your house (like the fridge, stove, TV), figure out how many hours each appliance is being used during the course of a day, and write down how much power they use in watts. (You can usually find this on labels on the device or online.)
For example, if you use your stove (3000 watts per hour) for 1 hour a day, you would write 3,000 watts x 1 = 3000 watts. If the TV (150 watts per hour) is on for 5 hours a day, you would write 150 watts x 5 = 750 watts.
If you add up all these watts used, you’ll start to get a good sense of what your home might use in watts every day.
Then, take the total of those watts and divide them by 1000 to get kilowatts (kW). For example, 3750 watts ÷ 1000 = 3.75 kW (or you can just go to google.com and search “3750 watts in kilowatts” and Google will do the math for you. lol)
Each Powerwall can store 13.5 kWh (kilowatt-hours, or 1000 watts per hour). You can connect up to 10 Powerwalls together to give you more kilowatts per hour, but there are some other things to consider when trying to figure out how many Powerwalls you need to get.
Limitations of Powerwall
Home batteries have limitations for their power output.
The Powerwall has a cap at 5kW continuous power with a peak load up to 7kW. These limitations are per Powerwall. So, if you have 2 Powerwalls, you now have a maximum of 10kW continuous power available.
Continuous Power: The long-term wattage that the Powerwall can supply normally.
Peak Power: The wattage that the Powerwall can supply for a very short period of time when starting an appliance.
So these caps might mean you can’t have all of your appliances on at once unless you get more Powerwalls connected together.
If you want all of your appliances running at the same time, you’ll have to add up how many watts per hour they all use and make sure your network of Powerwalls can handle it.
How many Powerwalls you need to power a home really depends on what your goals are with a battery backup. If you just need an emergency battery backup when there’s a power outage, and your goal isn’t to get 100% of your appliances up and running, you might be just fine with 1 Powerwall.
And make sure to let the Powerwall installer know of your goals. Let them know if you want all your appliances backed up by the Powerwall, or if you’re just looking for a few things to work during a power outage (like the fridge, lights, TV, and desktop).
Another thing you’ll want to discuss with your Powerwall installer is if you want a major appliance, like your HVAC, to work during a power outage. Major appliances like an HVAC have a big spike in power usage when the motor starts.
Since 1 Powerwall has a peak load capacity of 7kW, you risk tripping the Powerwall’s emergency shutdown if you overload it when something like your HVAC kicks on in a blackout. (Your installer might recommend a “soft start” for something like your HVAC… without too many details, just let your installer know if you plan on using an electric-guzzling appliance when there’s a power outage to make sure everything is all good).
Solar Panels vs Winter
Also, consider that wintertime will be your lowest solar production if you’re planning on charging your Powerwall solely with solar panels.
But a really cool feature is Storm Watch.
The Powerwall’s system will detect storm warnings, will automatically charge your battery up to 100% the night before the storm, and keep it charged until the storm is supposed to hit.
How cool is that?
Overview: Can Tesla’s Powerwall Power a House?
Most people can run an entire house with just 2 or 3 Powerwalls, and that seems to be what most people settle on.
One Powerwall could also be totally fine if you just need it for a power outage and you’re fine with cutting back on your energy usage at that time.