How Many Tesla Powerwalls To Go Off-Grid? (A Look at Both the Powerwall 2 and Powerwall+ & How Many You’ll Need To Power a Whole House)

How Many Powerwalls To Go Off-Grid?

Most people can run an entire home with just 2 or 3 Powerwalls, and that seems to be what most people settle on.

But how many Tesla Powerwalls would you and/or your family really need to go completely off-grid and keep living the same lifestyle as you’re accustomed to?

While the price of Tesla’s Powerwall batteries has come down since they were first introduced, they are still not cheap. So before making the decision to purchase 2* or more of these batteries, it is important to do your research and figure out exactly how much they will benefit you.

You’ll first need to calculate how much electricity your household uses on a regular basis.

* Powerwall’s Off-Grid system requires a minimum of 2 Powerwalls.

How To Calculate How Many Powerwalls You Need

When calculating how much electricity you use in your home, it is important to understand the difference between kWh and kW. A kW measures instantaneous power usage, while a kWh measures energy used over time.

To size a Powerwall system for your home, you need to know how many kWh of energy you use on an average day. This will help you decide what size battery is right for your needs.

Knowing your home’s energy requirements is also important when deciding if a Powerwall is right for you. If you only use a small amount of electricity each day, a more traditional solar power system or portable power station (Amazon) may be a better option than a Powerwall.

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Home Energy Needs

If you don’t have an energy monitoring system 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) for 1 hour a day, you would write 3,000 watts x 1 = 3000 watts. If the TV (150 watts) is on for 5 hours a day, you would write 150 watts x 5 = 750 watts. If you add up all these watts used during a typical day, you’ll start to get a good sense of what your home might use in watts daily.

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.)

How Many Tesla Powerwalls Are Needed?

For the rest of this example, we’re going to take the average electricity consumption of a US family of four, which is 27 kWh per day.

Since each Powerwall unit can store 13.5 kWh, you would think that a family that uses 27 kWh would only need 2 Powerwalls to give us enough power every day. Right?

13.5 kWh x 2 = 27 kWh

But not so fast!

Days of Autonomy (Off-Grid Backup Power)

Even though you might think that you only need a Powerwall system that can supply us with 27 kWh every single day, we also want to have enough power for backup, or what is called “days of autonomy”.

Typically, a good figure is 3 to 5 days of autonomy. So what this means is if you have a cloudy, rainy, or snowy day, you will have enough backup power to power your house during that duration of reduced solar power output.

So, if you live in the United States where you can sometimes get up to 3 days of rain, you would multiply your home energy needs (in this case, 27 kWh) by 3. If you live in a cold climate, let’s say in Northern Canada, then you might want to multiply your home energy needs by 5.

So let’s say we decide that a 3 days of backup power is good for us, we multiply 27 kWh by 3 to get 81 kWh (which should be the total size of your home battery system).

Since each Powerwall gives you 13.5 kWh, then you would need 6 Powerwalls to go off the grid.

How Many Tesla Powerwalls Can Be Used Together?

You can connect up to 10 Powerwalls together to give you more kWh, but there are some other things to consider when trying to figure out how many Powerwalls you need to get.

Keep reading…

Powerwall & Power Limitations

All home battery systems have limitations in the amount of energy that can come out of the system at once.

Here are 2 terms you want to know when trying to figure out how many Powerwalls you want to get for your home; continuous power and peak power.

Continuous Power: The amount of power that the Powerwall can supply continuously (long-term).

Peak Power (sometimes called peak surge power): The maximum power that the Powerwall can sustain for a very short period of time when starting an appliance. Powerwall’s peak power lasts about 10 seconds. (Appliances like an HVAC have a big spike in power usage when the motor starts. Your Powerwall installer might recommend a “soft start” for these types of appliances.)

A 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.

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.

Conclusion: How Many Powerwalls Do You Need?

A Tesla Powerwall might not be for everyone.

For example, if you only need to power small appliances and charge devices like a phone or laptop, a smaller battery bank or portable power station (Amazon) may be sufficient.

My wife and I have been living off-grid for awhile now and we solely live on our Ecoflow portable power stations (Amazon) and Renogy solar panels (Amazon). We have the River Mini, the River, the River Max, The River Pro with an extra battery, and an Ecoflo Delta Pro to run our entire off-grid home (my wife and I also work full-time from our home office).

However, we are very aware of how much energy we use and we downsized our fridge to a 58-quart Alpicool CF55 Portable Refrigerator/Freezer (Amazon) and got a gas-powered generator (Amazon) to run our washing machine and dryer.

Nevertheless, if you want to live completely off-grid and you need a system to run your entire house (especially if you have kids or you use a lot of electricity), then you really should think of investing in a bigger solar system like a Powerwall.

For an average-sized home, off-grid configurations will probably demand 2 to 3 Powerwalls, depending on the climate. And keep in mind that you’ll need an internet connection for your Powerwall system to work completely.

Also, you really want to buy as many solar panels as your Powerwall system and budget will allow. Solar panels are cheaper than batteries, and it makes sense to spend a little more money to buy solar panels that can produce more energy than you need at any given time.

It is also advised that you include an alternative gas, diesel, or propane generator (Amazon) to your setup so that there’s an uninterruptible power supply.

One powerwall would be insufficient to completely power a house year-round. But how many Powerwalls you would need depends on a variety of factors, including the size and usage of the home, the climate, and the number of solar panels. Generally speaking, though, it is recommended that you have at least 2 or 3 Powerwalls in order to maintain a consistent level of electricity.

Yame Smith, OffGridPower101.com