Portland Tesla Powerwall: Everything You Need to Know

Here in Portland, we are no strangers to frequent earthquakes and subsequent power outages. However, with a Tesla Powerwall, you may be able to avoid this inconvenience and keep your power on, even during grid outages.
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    Tesla Powerwall - Portland, OR

    Here in Portland, we are no strangers to ice storms and the subsequent power outages. However, with a Tesla Powerwall, you may be able to avoid this inconvenience and keep your power on, even during grid outages. 

    What Does The Powerwall Do?

    The Tesla Powerwall is a battery backup system that’s designed to be used with residential solar energy systems to store electricity. There are three main uses for the Powerwall:


    With a Powerwall, you can store your solar energy for later use. During peak daytime solar energy production hours, your solar panels can power your home and often simultaneously charge your Powerwall, and then you can use that stored sustainable energy after dark when your panels are no longer producing. This allows you to self consume more of the solar power that you generate onsite.  

    Backup Power

    The Powerwall has a capacity of 13.5kWh, so it can sustain your home during grid outages. If you pair your Powerwall with solar, the solar system can charge the battery every day while the sun is shinning.  Here in Portland, if you have an adequately sized solar system, 2-3 Powerwalls, and keep your consumption low, you can run continuously from June to September without having to rely on the grid at all!  Now, unfortunately, most of our gird outages happen in the winter when the days are short and the skies are gray.  In those situations you’re really relaying on just the capacity in the battery because very little solar power will be produced those days.  In this scenario, a Powerwall can help you get through short outages (1.5 days or less based on average household energy consumption), keeping you comfortable and preventing the loss of spoiled food.

    Time-Of-Use Rate Avoidance

    Some utility companies charge time-of-use rates, where power is more expensive during peak times and less expensive in the middle of the night.  For now, most of the utilities in Oregon, and SW Washington have flat costs of power, meaning that the cost of power is the same during peak times and non-peak times.  That being said, in our utility districts, the Powerwall won’t really help with Time-of-Use Rate Avoidance.  

    However, Portland General Electric (PGE), does have an option Time of Use Rate Scale that you can elect to be on.  This could save you money over time with the use of a Powerwall because you can store your own power and use it during the highest rate peak times, and then pull from the grid when it’s cheapest (often in the middle of the night) to avoid purchasing energy during peak hours.

    Tesla Powerwall Specs

    • Weight: 251.3 lbs
    • Dimensions: 45.3 x 29.6 x 5.75 inches
    • AC Voltage: 120/240 V
    • Capacity: 14 kWh/13.5 kWh usable
    • Maximum Power Discharge: 7 kW
    • Typical Power Discharge: 5 kW
    • Round Trip Efficiency: 90%
    • Noise: < 40 dBA
    • Mounting: Floor or wall, indoor or outdoor`


    Max Solar Load is the maximum AC load of your solar system. AC loads are usually smaller than the rated DC load. DC load is simply the number of solar panels you have in your system times the wattage of each panel. For example (25) 320W panels would be an 8,000 watt DC system or 8 kW DC. To find the AC system size you need to know the continuous output on the inverter or mircoinverters. We like to use Enphase Mirco Inverters. In this example, we might have (25) IQ 7+s with an output of 295W each. That provides an AC load of 7,375 watts or 7.37 kW DC. Which would be perfect for (1) Tesla Powerwall.

    Max Breaker Load is the largest breaker in your panel that you could power with the designated amount of batteries. For example, (1) Tesla Powerwall can power breakers up to 30 amps. This is usually enough for lights and outlets, but not enough for AC, pumps, or electric heaters. With (2) Powerwalls you can power one breaker up to 60 amps at a time. With (3) Powerwalls or more you can now power multiple breakers up to 60 amps at the same time.

    The capacity is how much fuel you can store in the tank. Each Tesla Powerwall has 13.5 kWh of capacity and the more capacity you have the longer you can run without power and the more solar energy you can store overnight. Typically (1) Powerwall is only good for short outages and won’t last long without sunlight. However, (2) or (3) Powerwalls can typically get you through the night and beyond!

    Peak power is how much output a Powerwall can push out over a short period of time. Continuous Power is how much power a Powerwall can push out over an extended period of time. When looking at Peak and Continuous power for an appliance we want to evaluate the max amp draw and the voltage at which the appliance runs at. For example, an AC unit that runs 240v and draws 40 amps would require 9,600 watts (volts times amps) or 9.6kW. Now you can see why (1) Powerwall wouldn’t be sufficient to power this load, but (2) Powerwalls can do the trick!

    How Much Does A Powerwall Cost?

    The base Powerwall unit costs about $10,000 if you include shipping.  However, to function, the system requires the Gateway ($1,500), additional hardware ($1,500), custom design and permitting ($1,000), and installation ($4,000).  So the total cost to install one Powerwall is around $18,000.  The good news though, is that if you pair the Powerwall with solar, the batteries qualify for the 26% Federal Tax Credit, which greatly reduces the cost.

    Adding a second battery is a great idea!  Not only do you double your capacity, but you’ve already paid for the Gateway, Design, Permits, and most of the additional hardware.  An additional Powerwall is only another $11,000 installed which includes the labor costs and necessary hardware.

    How many Powerwalls do I need?

    Sizing Powerwalls can be tricky since there are a handful of variables to consider.

    • Solar Production – Depends on the size of the solar system and the day and time of year
    • Your Consumption – How much energy you use
    • Your Expectations – How long you want to be able to run without power (Battery Capacity) and what loads you want to back up (Battery Power or Output).

    Solar Production depends on the size of your solar system, the time of year, and the weather on that specific day.  Generally, from June to September solar systems in the Pacific Northwest over produce, meaning that they generate more power than the home might consume in a day.  Conversely, from October to May, the solar system will under produce.  That being said, if the grid goes out and you have sufficient capacity in your batteries (27 kWh to 40 kWh or 2-3 Powerwalls) you can run continuously from June to September.  Those same batteries however in December might only last you 1-3 days because very little solar production would be added to the battery with the short, cloudy days that we see that time of year.

    Your Consumption varies widely from household to household, however we suggest to homeowners that when the power goes out, try to use less of it.  That might mean turning off breakers in your Main Service Panel (MSP) so that you can allow your batteries to run longer.  That’s one thing that the SPAN Panel is great for helping to manage.

    Your Expectations primarily rely on two things; how long you want to be able to run without power and what loads you want to back up.  With (1) Powerwall you can back up loads such as lights and outlets.  When you add a second Powerwall, not only do you double your capacity, but now you can back up lights, outlets, and (1) large load such as your Dryer or AC.  The main limitation with (2) Powerwalls is that you can only run one large load at a time.  If you install (3) or more Powerwalls, you can now run multiple large loads at the same time (Dryer, AC Heat Pump, Oven, Pumps, etc.).  As you add more batteries, you increase the amount of time that you can go without power.  You also decrease your reliance on the amount of solar that’s produced while the grid is out.  The more the merrier, just keep the cost in mind.

    The maximum number of Powerwalls that you can string together is (10) for a total capacity of 135 kWh.  Although, the Tesla Gateway, which is the automatic transfer switch for the system, is also limited to 200 amps.  That’s plenty for most homes, however if you have a 400 amp service with multiple main service panels, you’d need to add (1) Gateway for every 200 amp panel.  Each one would act as it’s own independent system. 

    Where Can I Buy One?

    Currently, you can only buy the Powerwall system directly from Tesla Energy or through a Tesla certified installer like Power Northwest.  Power Northwest is certified to install the Powerwall and Tesla Solar Roof.

    Is The Tesla Powerwall Worth It in Portland?

    While the Powerwall isn’t cheap, it provides unmatched resiliency and back up, allowing you to integrate your solar system for a clean, seamless, back up power source in the event the grid power goes out.

    Tesla Powerwall FAQs

    Have a question about the Tesla Powerwall? Here is a list of the most frequently asked questions we get. If you still can’t find what you need, please feel free to contact us with your question.

    For the average household, 2-3 Powerwalls are usually enough to provide an adequate backup and storage system. However, larger households or those powering things like air conditioners, pools or spas, or electric vehicles may need more.

    Tesla guarantees that the Powerwall will still retain at least 70% of its capacity after 10 years according to their warranty, although the product can of course last longer.

    With an 8 kW solar energy system feeding it and no loads drawing power, the Powerwall can be charged in less than two hours. However, a smaller solar system, poor weather conditions, or using the Powerwall as it’s charging will all increase the time necessary to fully charge it.

    The Powerwall 2 has a Lithium Nickel Manganese Cobalt battery. This newer battery offers double the capacity and three times the power output compared to the Powerwall 1.

    The Powerwall can be charged with only one solar panel, although of course that will take quite a while. In fact, you could just charge it from the grid and not use any solar panels at all. The average home solar energy system is around 10 kW and is made up of between 20 and 30 solar panels, depending on their wattage rating.

    You can, but unless you are living in a very remote area, it’s often cheaper and much easier to remain tied to the grid. But, if you buy a property with no nearby power lines, it can be cheaper to install solar and a Powerwall than to run powerlines.

    At this point, Tesla has no plans to develop a Powerwall 3.  Currently, the Powerwall 2 will be manufactured and supported as the only AC Coupled Powerwall offering next to the Powerwall + which is a DC Coupled System.  Meaning that the Powerwall + only works with the Tesla String Inverter.  This is perfect for Tesla Solar Roof installations.


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