Western Solar Lays Out Details On Tesla Powerwall

MAY 24 2015 BY MARK KANE 39

Tesla Energy Powerwall Multiple-Packs

Tesla Energy Powerwall Multiple-Packs

When Tesla Motors introduces new products, it raises a lot of excitement, which seems to be the core strategy that enables Tesla to spread the word across the world without advertising.

Although not all seem to share the excitement. For example Western Solar, a company installing solar system in Washington, recently referred to the Tesla Powerwall products in a blog post to its customers in the state

Western Solar finds that Tesla Energy will not necessarily be a viable solution in Washington and pointed out several drawbacks that makes installation expensive.

Besides solar array, minimum cost could land at $11,000 – $15,000 for a single Powerwall unit.

  • Did Tesla just invent a new battery technology? Not really.
  • Do I need a battery backup system for my home? Not really except specific situations.

    “Most homes in our area probably don’t have much need for battery backup systems. If you’ve got a good connection to the electricity grid and grid power is reliable, battery backups don’t usually pencil out. If you’ve already got a Western Solar system, and talked with us at the time of installation about battery backup and decided against it, the answer likely hasn’t changed.

    Battery backups are mostly installed in situations where a customer wants to have a completely off-grid system, a customer experiences frequent power outages, or a customer is concerned about future events that may affect the stability of the power grid system.

    One major idea behind the Powerwall is that it’s designed for “peak load shedding” in California and other states where they have tiered utility rates structures that allow this system to be charged at night when rates are low and then be discharged mid-day when rates are higher. We don’t have tiered rates here in Washington, so the primary function of this system doesn’t apply.”

  • How much power will the Powerwall system store? Not enough energy or power until you add more units.

    “The Powerwall is not a backup alternative to a traditional generator. One of the most important issues we see is the extremely limited power output of the system as compared to other battery systems previously on the market.  The Outback Radian system that we currently install for these types of installations comes with a battery bank that has up to 58 kWh of backup with the ability to run a house for a couple of days.  The Powerwall comes with either a 7 or 10 kWh option and usually batteries cannot be discharged more than 80%, resulting in an availability of only 5.6 to 8 kWh of actual backup power.

    With the 5.6 to 8 kWh of backup power per unit, and using Tesla’s example loads on their Powerwall site, there is an extremely limited availability.  Assuming that you run absolutely nothing in your house but a refrigerator and three lights during an outage, you could run for 11 hours on the 7 kWh unit and 16 hours on the large 10 kWh unit.  If you used anything more than the refrigerator and three lights, this time would shorten dramatically.  For example, if it were winter and you simply tried to run a tiny plug-in heater along with the lights and refrigerator, this system should provide backup for only about 1.5 to 2 hours maximum. However, this system has a peak output rate of only 2 kW or 2,000 watts continuous, which is less than most tiny plug in heaters, again limiting this system to primarily lights and a refrigerator.  Multiple batteries may be installed together to provide a greater storage capacity, up to 63 kWh and 90 kWh for the 7 and 10 kWh batteries, respectively.”

  • What additional equipment is required to make the Powerwall system work, and how much will it cost to add to my system? A lot.  Even the smallest installation will in the end cost $11,000 – $15,000, not including a solar array.

    “The cost of the Powerwall to installers is $3,000 to $3,500, excluding the cost of an inverter and installation.  However, detailed specifications showing the installation of the system have not been released yet.  Without these specifications we cannot know exactly how this will interface with our solar systems and what we will need to charge for the system. Additional installation fees/requirements in place here in Washington will make the installations very complicated and much more expensive than what is being advertised.

    In order to use the Powerwall system with a solar array, you will need an inverter. Tesla has thus far announced two manufacturers that they have partnered with, whose inverters will work with the Powerwall system, however we currently have no details as to which additional inverters will be compatible. A grid-tied battery backup inverter that will interface with this system can run anywhere from $3,000 to $8,000 just for the inverter equipment, not including installation, and customers will want one of the Made-in-Washington inverters in order to qualify for the in-state incentives on the installation.

    Adding battery backup to a solar system also requires the installation of three meters, not just the two that are required for a traditional grid-tied solar installation. These meters are substantially more expensive, with the PSE fee to the customer being $425 just for the meters alone after the installation is complete. For comparison, the standard cost for a PSE customer with two meters is $83.

    Installing a battery backup system also requires the installation of a “Critical Load Panel” where the backed up loads are isolated and moved to/from your primary electrical/breaker panel.  The fee for this can run from $500 to $1,000 on top of normal installation costs. This is a required component here in Washington and according to NEC code and is often difficult to install in some locations.

    All in all, for equipment alone, you’re looking at $11,000 – $15,000 minimum to install a battery backup system only, not including the cost of a solar array.”

  • How and when can I get one? Through Western Solar you can’t, at least for now.

    “The Tesla Powerwall is going to be sold through a dealer network.  Western Solar has put in a request to be a dealer, but we have not heard back from Tesla as of today. Once the Powerwall becomes available this summer, SolarCity, the largest solar company in the United States which is also owned by Elon Musk, will take the first shipments.”

Source: Western Solar

Categories: Tesla


Leave a Reply

39 Comments on "Western Solar Lays Out Details On Tesla Powerwall"

newest oldest most voted

Because of the way Washington State’s incentives are set up, including net metering, plus low electricity prices and no time-of-use rates, the Powerwall is not particularly useful here, and Western Solar’s article was talking about that.

It doesn’t mean that it’s not useful other places, like remote areas in developing countries or in areas where electricity is very expensive at certain times of day, or where net metering is unavailable or the grid is unreliable.

I think this company was shooting from the hip and haven’t really given it much thought. It sounds like a sell job for their products. The writer also took Washington’s case and used it to generalize the non-case for Powerwall.

This company doesn’t make their own products that compete with the Powerwall — they said they will sell the Powerwall once Tesla lets them. They’re just saying that battery systems aren’t particularly useful in Washington.

You’re right that the InsideEVs author didn’t do a very good job of making it clear that the original article was written to answer questions from Western Solar’s customers, all of whom would be in Washington State.

It is pretty accurate from what I can tell. Washington state requirements seem a bit over the top.

Care to point to anything that you believe is incorrect?

Stating facts for one case doesn’t make it true for all cases. Care to disagree?

Maybe the article was edited in response to your first comment. But it seems pretty clear that these statements were directed at people in Washington.

“Western Solar, a company installing solar system in Washington, recently referred to the Tesla Powerwall products in a blog post to its customers in the state

Western Solar finds that Tesla Energy will not necessarily be a viable solution in Washington and pointed out several drawbacks that makes installation expensive.”

But the situation may be similar for people in other areas and thus it may apply to them too. As Peder pointed out, the Powerwall doesn’t really make sense for people in California with net-metering:

Whoa! This is devastating. A refridgerator plus three lights? A small space heater for 2 hours?

Don’t get too depressed. I don’t know where that company got the idea that small space heaters are more than 2 kW, but that is very much not true. My in-laws use a lot of those things (and my wife has one) and they are generally on the order of 1 kW to 1.5 kW. Still a lot, but definitely not more than 2 kW. Hell, my heat pump uses just about 2 kW!

Space heaters are typically between 1kW to 2kW. My family used them as the main source of heat for years, and you need 2kW per room even in fairly mild climates where it never gets below freezing.

That already maxes out the Tesla unit, so true, one unit wouldn’t be very useful. I originally suspected they intended multiple units to be used, but there’s still no info out on daisy-chaining them, so it’s unclear.

Well, if you are using resistant electric heat to heat a home, you are already doing it wrong.

Anyone with solar panels plus energy monitoring that actually watches it a little can lay out real usage facts. I have an eGauge energy monitoring with my solar panels and can tell you specific usage patterns for just about anything in my house. Energy efficient refrigerator consumes 100 Watts while running and maybe 3 watts in idle, spends about 1/3 of the time running so about 35 Watt Hours per hour. 3 LED light bulbs running for an hour is 30 Watt Hours, 3 CFLs = 45 WH, 3 incandescent = 180 WH (all assume about 60 watt comparable output/600 Lumen or so). So, energy efficient refrigerator + 3 LED bulbs = 65 WH / hour, assume 80% of that 7KWH battery pack = 5600 WH, divide by 65WH / hour and you have about 86 hours of run time for those. You would have to assume worst case scenario to come up with their 11 hours – old refrigerator running non stop consuming 300 Watts and incandescent bulbs = 480 WH / hour – 5600 /480=11.6 hours. Who is going to spend the money on solar + battery without first getting reasonably energy efficient first? You can replace every… Read more »

Nice back-of-the-envelope numbers. I wouldn’t mind installing a powerwall as a little backup system just for the fridge & a few LED lights.

I’m not sure what type for refrigerator or lights they are using.

An energy star Refrigerator uses about 500 kWh of electricity per YEAR. So at 1.3kwH per day, you could run for over 5 days on the 7kWh battery (more if the solar panels charge the battery during the day)

Similarly a 60W equivalent LED bulb is 4W, or .096 kWh per day. You could run 10 of those bulbs for more than 7 days.

Now if they are using a Refrigerator from the 1976 at 2200 kWh per year and old incandescent light bulbs, the number are much worse.

I don’t know how they got to those numbers, but they sure aren’t right. A modern fridge uses ~ 1 kWh per day and an LED light is 5-10 W.

You won’t use the light 24/7, but say, 10 hrs per day. 10 hrs * 3 lights * 10 W = 300 Wh per day.

So in total the fridge plus three lights is 1.3 kWh per day and you can sustain that from the 7 kWh battery with net 5.6 kWh available for 4 days.


I tried to get some clarification from Solarcity, since they are currently the only ones here in MD, that offer the Powerwall. The multiple salespeople, that I contacted and contacted me didn’t even know the difference between the 7kWh(daily cycling/backup) and 10kWh(occasional backup in case of outage). The last SolarCity rep I spoke too told me, that the 7kW-systems are currently offered on HI only.
None of these units are working with the DC-connector of an EV, which is what I was after. Nissan has a V2G-system in Japan, but it’s not available anywhere else yet.

I think a more appropriate title here should be “Western Solar Lays Out Details on Tesla Powerwall for Washington Residents.” I also found their comparing Outback Radian’s lead acid battery backup systems to Tesla’s Li-Ion battery backup systems disingenuous. They mention you can’t discharge these batteries more than 80% and they are ASSUMING that the rated 7 kWh/10 kWh does NOT account for that difference. And that’s not even getting into the fact that Lead Acid’s useful SoC is a pathetic 40% – 60%, so you’re really only using 20% of the full capacity! And the maintenance. And the terrible cycling and short life span. Need I go on? As for their equipment cost run down, I can’t speak for how Washington works, but here in California, there are no made-in-California incentives on inverters and most of the equipment they refer to is required with a new solar system anyway. My solar has a critical load box and I don’t think you need more than the one if you have your solar and batteries on the same circuit. Same with the meters. Again, I don’t know if this is a Washington thing, but I have three meters, the house meter,… Read more »

Absolutely, the author needs to make it more clear in this InsideEVs article that the original article is written to Washington State residents.

As you noted, the incentives and other programs are vastly different in different states. The differences in how many meters are needed have to do with the way the state incentive program works in Washington. And there are no “EV” meters in Washington, because everyone pays the same low rate for power all the time.

Also, I don’t think they’re really saying that Outback battery systems are vastly better than Tesla’s or anything. They’re saying that neither is really a great idea in Washington.

“As for their equipment cost run down, I can’t speak for how Washington works, but here in California, there are no made-in-California incentives on inverters and most of the equipment they refer to is required with a new solar system anyway. My solar has a critical load box and I don’t think you need more than the one if you have your solar and batteries on the same circuit.”

Well, for a generic grid-tied solar PV system, you won’t have a critical load box. You’ll just dump the solar PV generated electricity into the main panel. You’ll only have such critical load box if you were building a system with battery back-up or plan to have battery back-up in the future.

Yes, you are correct. I was thinking of something else when I said that. My solar has a secondary panel that is a grid disconnect panel with a switch. I think it’s to protect from power surges. The way the setup works is this: electrical line from panels into inverter, then another line from inverter to grid disconnect, then grid disconnect into main panel.

Perhaps people will begin to realize that this whole dog & pony show was done to calm investors and their partner Panasonic. Tesla wanted to show that the gigafactory will have other customers besides just tesla cars thus reducing the risk that the gigafactory will be a big white elephant.

The powerwall market is tiny now but will grow. There’s some market for the powerpack now though.

“Tesla has thus far announced two manufacturers that they have partnered with, whose inverters will work with the Powerwall system, however we currently have no details as to which additional inverters will be compatible.”

Does anyone know which inverters these are?

This is purely off the top of my head, but I believe one of them is Sunnyboy. Don’t recall the other one.

Fronius seems to one.

Given Solar City already announced a $7000 price with inverter and installation (which people already think is on the expensive end), I don’t see where they get the $11-15k minimum from.

And peak power rate is 3.3kW, even though continuous is 2kW. It’s smaller than I expected, but it might be the bi-directional rate (the battery should be able to handle 7kW/10kW discharge easily, so bottleneck is not on battery, might be the DC-DC converter).

It also contradicts itself. It says it carries a system that can be configured up to 58kWh and then complains about the 7kWh/10kWh of the Powerwall. Then further down it mentions the powerwall can be configured up to 63kWh/90kWh.

It also puts another 80% factor on Tesla’s 7kWh/10kWh nameplate rating, however, battery density math (pack is much heavier than capacity suggests even factoring in module weight) makes it so that the packs itself likely already has that limited discharge factored in (also something as large as 80% factor doesn’t seem applicable to lithium-ion; the Roadster used a SOC window from 95%-2% or 93% overall).

Perhaps $7k if installed at the same time as a PV system since the inverter supports both PV and battery.

As Tyrel mentioned above, I believe that Western’s cost estimate is based on installation in Washington, which the article did a poor job of making clear. Apparently Washington has some…interesting…building code standards.

I think you can up the peak and continuous power through linking more than one of these through series connection (I think, electrical engineering was never my strongest point). But this is probably geared more towards peak shaving for those who pay peak charges (usually $/kW above a certain threshold, usually around 2 or 3 kW).

Yes, it does contradict itself, quite a bit.

Yes, I also found that a bit screwy myself. Especially since the battery backup system they do install for their customers uses Lead Acid which was, from my point of view, an apples to turnip comparison.

I believe the $7k figure is for installation of a leased system from SolarCity.

They assume, perhaps with justification, that Solar City will get priority access to the Powerwall at least as the supply is production constrained (ie. until the gigafactory is up and running). One could imagine Solar City winning new customers with the line that they will be able to provide a compatible backup battery solution before Western or any other installer can. If Western can convince their potential customers that battery backup is not a valuable feature in their territory, it neutralized that selling point.

Well, Western is right. It doesn’t really make much sense to get unless you are off-grid, have a really unreliable local grid, are a prepper, or (I’m adding this one) you have lots of money and don’t want to be inconvenienced ever by loss of electricity. That last one will cover lots of rich silicon valley people.

Well, to be fair, those rich silicon valley people probably have PG&E. You can plan your calendar around their power outages. And hope they don’t blow up your neighborhood.

Speaking as someone who used to design and sell off-grid RE systems back in neolithic times (early ’90s), I’d say their answers to their Washington customer’s questions is factual and objective. It should be noted that the Powerwall is likely going to be installed by customers who are on-grid currently, and I completely agree with Western Solar that unless you have frequent power outages, or tiered and/or exorbitant electric rates, installing a battery system if you’re on-grid makes little or no financial sense. As for comments re the likely loads, on-grid customers are unlikely to have gone as far along the energy-efficient appliances route as off-grid customers have to, because it’s far less-cost-effective to do so. 7 or 10kWh is minimal back-up for an off-grid system which has taken all the efficiency reduction steps already, and which is typically designed to provide 3-7 days of stand-alone power. For the typical on-grid home’s power needs, 7-10 kWh is more of a UPS for the refrigerator and a few critical lights (even CF or LED), just as Western Solar states. On-grid houses aren’t using SunFrost refrigerators and other super-efficient appliances (Energy Star can be better than what was available 25 years ago,… Read more »

It’s not objective when they write “However, this system has a peak output rate of only 2 kW or 2,000 watts continuous, _which is less than most tiny plug in heaters_”. As someone else pointed out, if you have a tiny plug-in heater on a 120V/15A circuit, some simple math tells you that the tiny heater won’t use more than 1.8kW AC. That should be enough for any potential customer to run away from that company.

Huh, what kind of refrigerator and lights are they using? Checking my power usage online, even when I’m watching TV with the lights, DVR, and various other things plugged in and drawing power through the house (refrigerator included), my power usage varies from 0.5 kWh to 1.2 kWh. That lines up pretty well with the 11 hour mark, but it’s running basically most everything I use regularly, and 11 hours for the 7kwh daily cycle battery sounds like it would be pretty perfect for that purpose.

I think this battery pack up system would be more useful for wealthy people in counties who need 24 hour power service when the power grid runs out of fuel.

Here is s a story about fuel running out in Nigeria http://www.msn.com/en-us/news/world/nigerian-airlines-cancel-flights-amid-fuel-crisis/ar-BBkaPd2?ocid=EIE9HP

The trouble these people are facing is that the power grid needs huge diesel generators to run. Also everyone has a small portable gas powered generator to run when the grid stops producing power. In that the grid due to fuel and energy short falls only runs a few hours a day.

Think of what would happen if this county added 4000 to 5000 megawatts of none diesel running solar power.

Gilberto Quezada Jurado

Sale mas caro el caldo que las albondigas. money, money everybody wants to f×+k somebody

Don’t give Western Solar too much crap. They are actually price-competitive on solar installs in WA. If I was in their geographic area they would get my business.

if the CEO of Western Solar where to sell vehicles he would starve to death after convincing every person that walked in they did not have a need for a second or third vehicle. I can understand the concept may not be fully feasible in the state of washington, however a company should at least focus on whatever good selling points exist instead of dwelling on its given flaws for a specific situation. If wester solar is a public company, shareholders must take immediate action or suffer the consequences of such idiocy.

lol… so essentially they are saying, “we have put in a request to be a dealer but are butthurt that Solar City will receive the first shipments because of their ties to Tesla and Elon Musk… so in the meantime, Powerwall is a terrible product and won’t work for you… until we get approved as a dealer, then it will be awesome.”