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Tesla’s Incredible Shrinking Powerwall Warranty

July 2, 2016

By Paul Homewood 




It appears that Tesla have been quietly making their Powerwall warranty pretty worthless.

John Peterson, a lawyer and expert on energy and sustainability issues, writes in Investor Intel:


On June 21st, Tesla Energy quietly eviscerated the limited warranty for its 6.4 kWh Powerwall “energy storage for a sustainable home.” In an earlier version of the Powerwall Manufacturer’s Limited Warranty Certificate (USA) which is no longer available online, Exhibit A specified the following minimum capacity retention levels:


  1. The Product shall maintain >85% of its initial rated capacity until the earliest to occur of:

(a)        The lithium-ion battery cells in the Product have reached 4 MWh of aggregate discharge throughput (at the battery DC output); or
(b)       2 years have expired from the Original Installation Date.


  1. The Product shall maintain >72% of its initial rated capacity until the earliest to occur of:

(a)        The lithium-ion battery cells in the Product have reached 9 MWh of aggregate discharge throughput (at the battery DC output); or
(b)       5 years have expired from the Original Installation Date.


  1. The Product shall maintain >60% of its initial rated capacity until the earliest to occur of:

(a)        The lithium-ion battery cells in the Product have reached 18 MWh of aggregate discharge throughput (at the battery DC output); or
(b)       10 years have expired from the Original Installation Date.


While I didn’t think it necessary to archive a copy of the original Powerwall Manufacturer’s Limited Warranty Certificate (USA), I was able to find somebody else’s archived copy of Tesla Energy’s January 22, 2016 Powerwall Manufacturer’s Warranty Certificate (Germany) which uses this graphic to show the minimum capacity retention levels during the warranty period for a Powerwall with a daily duty use profile.


Tesla Powerwall Capacity

In a May 6th article titled, “Solar Panels and Battery Storage ­ Heaven or Hell?” I explained,

Traditionally, the battery industry has used a 20% capacity loss as the definitive end-of-life metric because most batteries lose capacity rapidly once they cross the 80% threshold. It’s my understanding that lithium-ion batteries do lose capacity more slowly than other chemistries, but I don’t have a deep enough knowledge of the technical aspects to judge whether Tesla Energy’s capacity retention estimates are conservative or aggressive. In fact, I’m not sure that Tesla Energy knows the definitive answer in 2016 because current estimates are based on computer modeling rather than real world performance data over a 10-year service life. Since human beings are far more clever than computers when it comes to abusing their stuff, I’m not willing to assume that the current estimates will prove to be realistic over the long term.

It appears my speculation about Tesla Energy’s confidence in their capacity retention warranty was well founded because the revised Tesla Powerwall Limited Warranty (USA) published on June 21st eliminates the specific capacity retention requirements of Exhibit A and relies instead on a sweeping exclusion that says:

In addition, this Limited Warranty does not cover (a) normal degradation of your Powerwall’s energy capacity over time; (b) normal wear and tear or deterioration, or superficial defects, dents or marks that do not impact the performance of your Powerwall; (c) noise or vibration that is not excessive or uncharacteristic and does not impact your Powerwall’s performance; (d) damage or deterioration that occurs after the expiration or voiding of the warranty period; or (e) theft of your Powerwall or any of its components.

Under the original Manufacturer’s Limited Warranty Certificate (USA), there were iron clad performance standards that told customers exactly what they could expect over the useful life of a Powerwall. Under the revised Tesla Powerwall Limited Warranty (USA) there are no standards whatsoever.

Apparently “normal degradation of your Powerwall’s energy capacity over time” is an ad-hoc decision that Tesla Energy will make in the future as warranty claims arise.



If Tesla are not even confident enough to quantify what “normal degradation” is, it can hardly inspire potential customers. This also appears to be evidence that Tesla’s finances might not be all they should be.

  1. July 2, 2016 7:22 pm

    That warranty never made sense. Market splash, then stealth change to no warranty beyond manufacturing defects.
    Neither does Tesla. Fast charging to overcome range anxiety increases battery degradation and shortens battery life. It is simply not possible to get appropriate range for a general purpose auto except in a full hybrid (Prius) or a range extended EV (Chevy Volt, max 40 miles electric only range). Tesla has never made money even with all its subsidies and sales of California emission credits. The only question is when to put on the big short position.

    Full hybrids make imminent sense even with current oil prices. We drive a MY2007 full hybrid Ford Escape AWD with class 1 tow hitch for fishing boat and motorcycles. Small SUV. 120 HP Atkinson cycle 2 liter I4 with 80 HP electric machine, idle off, 80% regenerative braking (battery charged by deceleraring/braking), ability to run all electric under 20mph until battery management kicks engine on (charge floats between ~48and ~52% to max battery life– on minor grades we have run up to several miles all electric on gravel forest roads at 15mph. Pulling away from full stop is electric only, acceleration is electric boost. Regular gas. 32 mpg city, 28 mpg highway at 65MPH, 27 at 75-80mph, 26.5 with AC on. No change since day 1. We do about 8-10 k miles/year, and saved about $1500/yr on gas (crude at $80-100) compared to equivalent AWD 3l V6 Escape requiring premium gas. Hybrid upcharge was $3500. Hybrid upgrade paid for itself in just over 2 years with no vehicle performance sacrifices. We are still saving $750/yr with crude at $50.
    There are 2wd versions of this hybrid Ford Escape in NYC cab fleet that have reached 300,000 miles with the battery still good. We are at ~80,000, zero sign of any problem. No significant service repairs, either. Just oil, lube, filters, wiper blades, second set of tires, one engine sensor.

    • July 3, 2016 12:33 am


      I recently purchased a 2010 2WD Escape Hybrid for the reasons you noted above. There are many used in San Francisco as taxis that have exceeded 300K with no battery swap and more importantly NO NEED FOR NEW engines or transmissions. San Francisco hills and streets are so punishing to vehicles that several automakers give free units to cab companies here for stress testing.

      Escapes also seem to have lower accident rates than other vehicles, also contributing to the low cost of ownership. It’s a real shame that they stop making them after 2011.

      • July 3, 2016 10:12 pm

        CtM, you will be pleased. The other thing about the first generation Escape (hybrid or not) was its very clever engineering. It is a frame rail vehicle–what gives it the towing capability we use. Like F series pickups. But on the front end, everything foreward the axle mount/frame rail end is just bolted on stamped sheet metal designed to crumple and absorb impact. Even the stamped frame extensions to which all else bolts, such as radiator, fan, bumpers, headlights, grill. We slid off our mountain cabin driveway in North Georgia (Inholding of Chattahoochee National Forest) in 4 inches of slushy snow one Christmas morning several years ago trying to go to church in Blue Ridge. Snow compacted to slick ice on a steep driveway (about a 25 degree slope), AWD helped but not enough, we almost stopped at the 90 degree right turn below the cabin–but not quite. So went over the the edge and down the mountain into the forest, even taking out a 8″ pine sapling along the way. About 30 feet of vertical in about 75 feet of horizontal because the driveway is dozer cut into the mountainside-so down mountain is even steeper than the natural mountain slope. Took a week for the roads to clear enough to get a wrecker in to winch the Escape back up to the driveway (using the frame rail mounted tow hitch) and out to Blue Ridge. We were assured it was a complete total loss.
        Wrecker took it into Chattanooga, nearest Ford dealer with full body repair. We were going to scrap it out after insurance adjuster confirmed total. Not totaled by a long shot. In a month, they had it back together good as new. What saved us was all the front crumple zone stuff just bolted onto the frame rails. Unbolt, rebolt new crash parts, paint. Guts of car was perfectly fine. Wheels did not even need realignment when checked.
        So whether or not Escape hybrids have fewer accidents, they are easier to repair than unibodies, and so have lower insurance rates.

  2. manicbeancounter permalink
    July 2, 2016 10:53 pm

    I think Tesla have miscalculated the 10 year part of the warranty.
    If you assume a daily charge, then the following figures are calculated.
    6.4kwh*85%*365*2 = 3.971Mwh. That is the 4Mwh over two years.
    6.4kwh*72%*365*3 = 5.046Mwh. Add to the above gives the 9Mwh over 5 years.
    6.4kwh*60%*365*5 = 7.008Mwh. Add to the above gives 16Mwh over 10 years.
    The 18Mwh is seems to have been calculated by taking the expected output over 5 years and doubling it.

    • Graeme No.3 permalink
      July 3, 2016 10:24 am

      Ah! But if you only use 1 kwh per day…. Battery dead Sir? Did you exceed the limit?
      Bad Luck!
      Although it is likely that Tesla’s bankruptcy will prevent that scenario. Obama only has 7 months to go ( and less if you include the lame turkey time).

  3. July 3, 2016 9:28 am

    Tesla’s warranty: now you see it, now you don’t.

    ‘Clean’ energy claims fizzle out yet again.

  4. July 3, 2016 12:23 pm

    More green BS, sold to “green” bozos.
    Can’t say I feel sorry for them.
    A fool and his money are soon parted.

  5. July 3, 2016 1:24 pm

    Reblogged this on Petrossa's Blog.

  6. Coeur de Lion permalink
    July 3, 2016 2:08 pm

    I get 54.3 mpg out of my diesel medium sized Citroen Picasso and am happy with that. (English Gallon)


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