How many solar panels should you install with a Powerwall 2?

powerwall and solar mix up

Installing more rooftop solar is a better investment than a Powerwall 2, so always rack up as much solar on your roof as you reasonably can first. Unlike this guy.

The Tesla Powerwall 2 is going to be big.  Really big.  I mean that literally and not figuratively.  It’s going to be big as in 13.5 kilowatt-hours of storage big.  From the point of view of most Australian households that is huge.

This large capacity presents households with two main problems:

  1.  It is more than the average Australian household uses at night.
  2. Those that do use that much electricity overnight may not have a rooftop solar system large enough to fully charge it.

So if the average Australian home buys a Powerwall 2 they will use it at less than its full capacity. As Tesla’s warranty is fixed at a maximum of 10 years, this increases the cost of each warranted kilowatt-hour substantially.

The obvious solutions are:

  1. Don’t install a Powerwall 2 unless your household regularly uses 12+ kilowatt-hours of electricity overnight.
  2. Don’t install a Powerwall 2 unless your solar system normally produces enough surplus electricity to fully charge it on a mostly clear day.  Normally this will require at least 5 kilowatts of solar panels.

[Read more…]

Should you go off grid with a Powerwall 2?


bloke with powerwall 2 cutting the wires to his house

Thinking of getting a Powerwall 2 and taking yourself off grid? Then you need to read this first.


Note from Finn:

Since this post was published Tesla have canned the DC Powerwall 2 in Australia. We will now only be able to get an AC Powerwall 2. A regular AC coupled battery is no good for off grid because it can’t talk to the solar inverter to balance energy demand and supply. So if you live in Australia and want to go off grid do not use a Powerwall 2.



A long time ago, back in the days before we knew how lame the original Powerwall was compared to its hype or how good the Powerwall 2’s hype is compared to the original Powerwall, I wrote about whether or not my parents in sub-tropical Queensland could save money by going off-grid using lead-acid battery storage.

My conclusion was they could not save money even under almost ideal circumstances.  The benefit of staying on-grid and receiving even a low feed-in tariff for surplus solar electricity was too great to make saying sayonara to the grid connection wire worthwhile. [Read more…]

Cost Of Powerwall 2 Drops 9% Overnight

powerwall 2

The Tesla Powerwall 2 is now $800 cheaper in Australia.

Tesla appears to be unsure about how much to charge Australians for the Powerwall 2.

Or maybe they are sure, but confused about how the Australian dollarydoo works.

Perhaps they’ve been confusing it with the New Zealand doubloon or the Fijian guilder?

I know I often do.

"Crikey! 900 Dollarydoos to the New Zealand doubloon and 6 centaroos to the Fijian guilder!"

“Crikey! 900 dollarydoos to the New Zealand doubloon and 6 centaroos to the Fijian guilder!”

[Read more…]

Powerwall 2 Full Spec Released: Low cost but ‘unlimited cycles’ warranty has limits.

powerwall 2 spec

The full spec and warranty of the Powerwall 2 reveal a cost per warranted kWh almost half that of its nearest rival.

[Update March 13: Tesla has cancelled sales of the DC Powerwall 2 in Australia and the first installations of the AC version of the Powerwall 2 will now apparently be done in April.]

Yesterday, Tesla kindly sent me the Powerwall 2’s full data sheet and warranty. We already knew the headline specs:

Storage: 13.5kWh

Power: 5kW steady, 7kW Peak

Price: AUD$8,000 + GST and Installation

But there were lots of questions over the exact configuration and warranty details that could make or break Tesla’s shiny new battery. Most of these questions have now been answered.

Here’s what the new specs reveal: [Read more…]

Is Tesla’s Solar Roof Fair Dinkum?

elon musk on tv

Tesla’s solar roof tile announcement raises more questions than it answers.

On Saturday the 29th of October, Elon Musk made an announcement that thousands of Australians were waiting to hear.

He spent 37 seconds making that announcement.

Then he spent most of the rest of the time spruiking Tesla’s new solar tiles. [Read more…]

The Tesla Powerwall 2: Batteries Can Finally Pay For Themselves

Elon Musk proclaims the coronation of Powerwall 2.0

Elon Musk proclaims the coronation of Powerwall 2.0

Today at 12:15 Eastern Standard Time, Elon Musk announced the arrival of the Tesla Powerwall 2.

Some people were enthusiastically looking forward to this announcement, but I was not. I fully expected to be underwhelmed, and as soon as Musk finished his two or three sentences on the actual system, I felt a near fatal lack of enthusiasm sweeping over me. [Read more…]

New LG Chem RESU Batteries: Smaller, More Powerful And Cheaper Than A Powerwall

powerwall and LG Resu 6.5 to scale

Smaller, cheaper, more powerful. LG Chem’s new batteries look very compelling compared to a Powerwall.

If you are in the market for a home battery and are tempted to buy a Powerwall, then I urge you to also consider the new range of LG Chem batteries announced last week.

Whilst LG have been unable to compete with Elon Musk for mainstream media coverage, the LG Chem RESU, or Residential Energy Storage Unit for the long winded, has been one of the biggest successes in on-grid home energy storage in Australia. While solid figures are hard to come by, it may have been used in almost half of all on-grid home battery installations.

[Read more…]

Misleading Statements On Sunrise Hurt Solar Industry


The scene in the Brakels’ household last Sunday morning.

On Sunday morning the program Sunrise had a segment on solar power and battery storage. While I am glad whenever popular TV takes the opportunity to educate people on these topics, that wasn’t what happened here. It was the opposite of education, as anyone watching it could easily come away believing the following three things:

1. Battery storage pays for itself.
2. Battery storage cuts CO2 emissions.
3. Rooftop solar needs batteries to be worthwhile.

None of these things are true.

Battery storage does not pay for itself when used on-grid and it may be years before it does.

Home batteries do not cut emissions, they increase them. In the future they may allow us to decrease greenhouse gas emissions, but that point is still years away.

Rooftop solar by itself is cost effective. It is adding batteries that can make it uneconomical.  The mistaken belief that rooftop solar needs batteries to be effective is causing harm to both the solar industry and the environment, as people are delaying installing rooftop solar until batteries become affordable. [Read more…]

Tesla Quietly Release New Powerwall Warranty: But There’s One Big Problem…

powerwall warranty

The new Powerwall warranty quietly introduced into Australia last month says you are not covered for ‘normal degradation’. Whatever that means.

Can I interest you in buying a revolutionary new energy storage system? It is called the Brakulator 7000. It has a usable storage capacity of 6.4 kilowatt-hours with a continuous power output of 3.3 kilowatts.  And the great thing is it comes with a 10 year warranty.

Are you interested? [Read more…]

ZCell Battery Review: Better Than Lithium-ion?

redflow zcell vs powerwall etc

How does the Aussie Redflow ZCell compare to lithium ion batteries?

The Australian company Redflow is accepting pre-orders for its new home energy storage system, the ZCell battery.  It has a 10 kilowatt-hour usable storage capacity, can provide 3 kilowatts of continuous power, and is suitable for on-grid and off-grid use.  Deliveries will begin in August 2016.

In this Z-Cell battery review I go deep into the zinc bromide technology’s pros and cons compared to its main challenger: lithium ion batteries.

While there are many lithium-ion storage systems on the market, the Redflow ZCell stands out as the only zinc bromide flow battery.  Its unique chemistry gives it several advantages over lithium-ion systems.  One is it can lie dormant for long periods at any level of charge without suffering from deterioration.  And another is its storage capacity will never decline over its over its entire lifespan.  [Read more…]