Tesla's New Powerwall Battery - Q&A's

By Kristy Hoare on in New Solar Technology

Update 28/08/2017: Tesla Powerwall 2 is now being produced, but availability in New Zealand is still limited.  Click here for Tesla Powerwall 2 specs.

Rongomai School was one of 130 winners of Vectors 'Future of Energy' competition. The competition was aimed at Auckland’s most deserving families, schools and community groups. Over the next few months, the 130 Tesla Powerwalls will be installed.  Once they are installed, Vector will announce the second phase of installs.

@Vectorltd Tesla Powerwall Install at Rongomai School

The Tesla Powerwall is an amazing new product that's about to come on the market in a few months time.  It is not completely revolutionary in terms of technology, but it is revolutionary in terms of making solar power storage available to a lot more people.  I would compare it to the ipod, where before there was mp3 players - basically this product is just a lot better than what we had before, and cheaper!

Elon Musk gives an amazing presentation about the Tesla Powerwall, check out the clip below.

Extra Information:

The 7kW Powerwall is meant for daily cycles, for example, solar powered homes that want to store their solar power collected during the day and to be able to use their power at night.

The 10kW Powerwall is designed for backup applications, for example, this system will be a good option for homes located in areas that frequently experience black outs.

Multiple batteries can be used in one home, up to 90 kWh total for the 10 kWh battery and 63 kWh total for the 7 kWh battery.

I've started to answer a few questions New Zealanders have about the Tesla Powewall.  If you have any questions please write them in the comments field below and I will endevour to answer them.

Are there any available in New Zealand?

Vector are importing the first 100 units in January 2016.

Do you have to go off the grid with a Tesla Powerwall?

No, when you get battery storage installed you can use as much of the stored energy stored as you like or as much as you can, then the power you use will seemlessly change over to drawing power from the grid or possibily solar power if it is being produced at the time.

You can go off the grid if you like, but you would need to make sure you have enough Powerwalls stacked up to make sure you will have enough power for your energy demand. It would be advised that you trial the Powerwall system first before you go off the grid. The true test would be to make sure you have enough power to live on over the coldest, darkest few days of winter.  Also you'll need to consider if there will be occasions you'd like to have more power e.g. if you have relatives to stay over at Christmas - there will always be a maximum amount of power you can use if you go off the grid. You could give it a trial - you could get the amount of Powerwalls you think you'll need to match your energy demand while staying connected to the grid, and when you are comfortable you could then disconnect.

What is the price for Tesla Powerwall?

A 7kW unit starts at US$3,000, which converts to approximately NZ $3978, and we can expect to see some shipping costs on top of that.

This is the game changer for battery storage, as in the past it has cost a minimum of $10,000 for battery back-up in New Zealand.  Battery storage with a solar power system has been hard to justify the cost in the past because the return on investment has been well above 10% ROI.  Depending on your power use patterns, I think for most people buying a solar power system and a Tesla Powerwall the ROI will be below 10%.

To compare prices for a solar power system and battery storage installed click here to go to our quote request form.

How is the tesla powerwall different from other batteries use for solar storage?

The big difference is that the batteries tesla are using are lithion-ion batteries.  The same type of batteries used in Tesla vehicles.  Traditionally lead-acid have been the most cost effective type of batteries used in New Zealand for solar power storage.

Lead-acid batteries are high maintenance, complicated to set-up, bulky, need ventilation and not pretty to look at.  The Tesla Powerwall is complete opposite.

How many cycles does the Powerwall 10kW pack last for?

One cycle a week for 10 years.

Is it just another toy for the rich?

Yes it kind of is. There is no subsidies for solar power and storage in New Zealand which keeps it away from people that it would benefit from it most. The Tesla Powerwall allows for cheap renewable energy that will be a big upfront cost, but will save the homeowner thousands of dollars over the years.

The good part is that the Powerwall will help smooth out the peak electricity demand curves. Those New Zealanders with one of these systems will have less demand for grid power in the mornings and in the evenings when there is peak demand. Less peak demand will mean the lines companies can relax a little, because when ever they put up their prices it usually to do with their costs for increasing capacity for peak demand.  So once there is a big enough up-take of solar battery storage in New Zealand, it will bring down the price of grid power for everyone.

Also, as Elon Musk points out in the video presentation, that the Powerwall will help people in remote areas that don't have access to power.  Tesla have brought the price for energy storage down quite significantly.  So for some people in remote areas who could not previously afford a small scale electricity generation system and have been going without, might now be able to afford one.

Will the Powerwall be able to connect with a solar power system that has micro-inverters?

With an Enphase micro-inverter system you are able to attached any generating source as long as it is made to comply to NZ electrical standards.

What is unknown at this point is how the system will be managed, so how it will balance the generation from the solar panels with the customers energy demand and send power to the grid?  The question remains; will the solar pv inverter be able to communicate with the Tesla Powerwall?  Many inverter companies have optional energy management systems, so the question will be whether the inverter will controll Tesla Powerwall or vice versa?

Enphase are bringing out their own lithium-ion battery storage system at the start of next year, therefore micro-inverter customers will definitely have battery storage options in the future.

Showing 25 comments

Posted by Kristy on 2017-04-21 13:06:42 PM

Hi Sheldon
Yes you can purchase them from Vector.

Posted by Sheldon Reddie on 2017-04-21 12:40:46 PM

Can Powerwalls be purchased in NZ as yet. If so where from and if not why not

Posted by Tiny on 2017-04-08 14:38:59 PM

If i understand vectors offer of a free power wall unit correctly it will cost me approximately $90.00 per year to run the built in cooling system and the only benefit to me will be limited power to some circuits when the grid goes down.(This does not happen often or for long where i live). Vector will control the system to ease demand on the grid at peak times for there benefit but i have to pay the running costs. Seems like a one sided deal to me.

Posted by Barry murphy on 2016-10-29 20:00:37 PM

Will the powerwall 2 be stocked by vector rather than the first generation? Comes with an inverter and double the storage capacity for the same price and same size

Posted by AKW on 2016-09-05 12:13:08 PM

We've been told the Tesla powerwall system can't be used off grid in NZ because there isn't an inverter available that can work in an off grid situation. Do you know of any lithium-ion battery systems available in NZ currently that can work off grid?

Posted by Kristy on 2016-08-25 16:14:00 PM

Hi Stefan

The Powerwall should be available to residential customers within the next month or two. Vector hasn't yet released specific dates.

Posted by Stefan on 2016-08-25 16:11:18 PM

I'm very disappointed that Vetor is not suppling the 3 phase version. They are available in Australia. When can I get one in New Zealand?

Posted by Superg on 2016-04-15 21:12:06 PM

When a battery specification refers to cycles, these days it means a "full cycle" even if composed of incremental parts of a cycle. So for example a 50% discharge, 40% recharge, 60% discharge, 60% recharge adds up to 110% discharge and 100% recharge. A cycle is 100% in both directions (effectively back to where you were in normal situations), so the example above is one half of 10% over a full cycle, therefore 1.05 cycles.

What this means is that if you buy a large enough power pack, you may indeed only use one cycle a week.
Battery performance does in fact reduce if you try to get 100% cycles at each use. For lead acid deep storage I believe a 40% discharge is the recommended limit to drop to, or perhaps 50%. I am led to believe the Tesla Powerwall has to some extent mitigated this perception by actually installing batteries larger than the rated specification and including management controls that reduce the discharge to less than 100% of the real capacity, but possibly close to 100% of the rated capacity.

It is indicative that a cycle of once per week is quoted, as that potentially infers that you should spec your battery system so that it can support you on 1 cycle per week, for best performance and longevity of the system. If they are giving a 10 year guarantee then there will be conditions and controls. The discharge level and the cycles per week is likely to be part of that.

It is really great to see the comments here and the discussion on controllers, compatibility and so forth.
I think the reference to above and below ROI 10% may be interposed in the story, as ROI is return on investment and a higher return is surely more attractive. Calculate what you spend, what you get back and the deduct what you would get leaving the money in the bank from the return or add the cost of interest if you are borrowing money, to the cost of the system.

There is a new type of PV panel being researched that could reduce the cost of PV panels to 10% of their current cost, provide almost the 7% conversion rate currently available, yet work at greater incident angles and lower light. These panels use chemical processes found in chlorophyl and oxygenating blood and the manufacture of these is magnitudes less harmful to the environment. We should see them by 2020.

PV panel salespeople will tell you there is no point in having a solar water panel as you can heat the water with electricity. But compare the energy efficiency of direct solar to water against PV panel to hot water cylinder and I think you would disagree. The only loss here would be if you over-specified the water heating panels and wasted some hot water.

Water is a very effective heat sink, if your intention is to draw heat rather than electricity, so worthy of consideration. Another option is electricity to heat eutectic concrete which can then heat water (and possibly do other work). The sums need to be presented for this.

What you are weighing up is simplicity against efficiency. It might be argued that the most effective system would only buy grid power on night rates, heat water and space heating with solar water panels and provide all electricity up to average daily demand from on-site generated electricity, and in addition charge your electric vehicle during the day.

Where is gets complex is that every time you convert energy from one type to another (AC or DC for example) or add and remove it from storage, or change it's work from say heating to lifting or moving, you lose a bit of efficiency at each conversion. So aim for minimum conversions which implies 'power where you need it, in the form you need it'. We all know that a petrol engine has a lot of waste heat converting fuel to motion.

As an aside, there are transmission losses when moving electricity from the power generation station to the consumer, (around 4%). Slightly less if the voltage is higher. Hence the reason for 11,000 volt lines and upward to 1.15 MV (Ultra High Voltage) on Ekibastuz-Kokshetau line (Kazakhstan) is that power is current x voltage, but more current creates heat from the resistance to flow in the conductor and that heat is just lost energy to the system. So much better to have the same power with massive voltage and less current. Of course there are limits to all this.

One argument I have heard espoused on the Tesla Powerwall is that it is not suited to a high power demand. So don't expect a Powerwall to concurrently drive a heatpump, oven and hot water cylinder for example. Do your research on this aspect. It perhaps adds more weight to the idea of using solar hot water panels as well. It may be that several Powerwall packs can indeed cope with this demand. Don't be scared off by the calculations, just be sure to get all the figures checked by an electrical engineer rather than relying on sales talk.

The opportunities abound, even if all you do is charge your car and provide your own daily base demand figure to save a few dollars. The mistakes are made with trying to do it all when you have a grid connection, or by assuming that now you have free power you will have 15 minute showers and install a heated swimming pool.

The unknown is how much power costs will rise, but we know that they have risen at about 4 times the inflation rate over the last 10 years since the industry was privatised, so until peak demand is lowered by large scale adoption of storage batteries this is likely to continue (essentially until supply exceeds demand).
The increase in electricity charges may fade into the background if you have to replace your entire investment every 10 years.

If you're not breaking the bank and you don't overthink it - you will feel rewarded by reducing generation demand and moving towards a sustainable future model of energy. Good luck.

Posted by Bright Kiwi on 2015-12-12 11:13:29 AM

Hi, having installed an AC system over 2 years ago I have seen it produce brilliant financial returns, even as far south as Dunedin! My ROI over the past twelve months has been 8.3% and since installation the overall return has been 19%.
Meridian's recent drop in feed in tariff has been a bit of a slap in the face however but until now installing a battery system to store power rather than give it away to the grid has been prohibitively expensive. These batteries may be the game changer that I am looking for.
Is it possible to indicate the likely cost of adding a battery to an AC system? Obviously there is no need for further inverters but I am assuming that there will be some sort of controller for switching power to and from the battery.

Posted by Kristy on 2015-11-04 11:52:15 AM

Hi Jan,

Only Vector has announced they will be stoking these batteries, and it will probably only be available to people in Auckland on the Vector network... to begin with anyway.

Posted by Jan Heijs on 2015-11-04 11:44:42 AM

Which companies are selling these batteries in NZ and is there an update on availability in NZ?

Posted by Kristy on 2015-11-04 09:30:08 AM

Just a quick update:

At present the only solar inverters compatible with the Tesla Powerwall are SolarEdge and Fronius. This is because the high voltage output of the Powerwall is not compatible with standard solar inverters.

Enphase have a similar lithium ion battery solution which is about to come out on the market, more details are here: https://mysolarquotes.co.nz/blog/new-solar-technology/launch-of-enphases-home-energy-solutions-2015

The Enphase AC battery is compatible with both micro inverters and all standard inverters.

Posted by Kristy on 2015-10-09 17:27:31 PM

Hi Figjam 001 and Ross

I believe the 10kW system would be suitable for battery backup scenarios. E.g. someone who experiences blackouts often. This model wouldn't be very popular because not many people require battery backup, especially at that price. However the 7kW Powerwall is made for daily cycles, so this would help someone with a grid connect system wanting to achieve higher self-consumption. The 7kW system also has a 10 year warranty.

Posted by Ross on 2015-10-08 14:39:44 PM

Does someone have an answer for the relevant question about the life of a battery used every day - as asked by FIGJAM in August?

Posted by Figjam 001 on 2015-08-04 10:45:39 AM

"How many cycles does the Powerwall 10kW pack last for? One cycle a week for 10 years"

So if I read this correctly the Power wall is only good for 1 Cycle per week 10 years?
Most Kiwis would want a solution that would allow power stored during the day to be used peak times EVERY DAY.

The maths says that this would only last if cycling every day for around 1.5 years.
You wouldn't even come close to getting a return on investment at that rate!

Posted by Pendowr on 2015-07-23 14:16:21 PM

Hi Kirsty,
We are currently assembling the final components for an initially 3 Kwh stand alone system in the marlborough Sounds. We plan to have sixteen 270W PV panels backed up with a wind turbine and diesel generator producing 48v DC managed through a 3kWh "Outback" system. I have yet to purchase the batteries and have been following with interest the Tesla entry into the market. We were initially thinking of using two banks of 6 six Volt 369 Ah Lead acid batteries. If we installed the proposed Tesla battery system with comparable deep cycle storage, how many packs would we need to use and should we increase the storage? Of course now that Samsung are saying that they are entering this market that too becomes an option when we have some idea of their proposed price.

Posted by Kristy on 2015-07-23 14:04:03 PM


It will be interesting to see how the Lithium Sulfur batteries perform. But I think it is likely that Lithium Ion batteries will be the type that will be more commonly used by households, because Lithium Ion has been on the market for a long time, used by all cell phones and laptops.

There are quite a few other companies that are about to launch Li-Ion solar energy storage including Enphase, Bosch and Samsung which all will be really good competitors for Tesla.

Posted by ARKKIWI on 2015-07-18 08:15:09 AM

Looks like there are others competing with Tesla. Any thoughts on the following:


Posted by Kristy on 2015-06-04 13:19:42 PM

Hi Daniel

I would assume that management for the battery would be at an extra cost because they haven't said that the powerwall definitely has it's own management system. Also I have read a few articles that say Tesla have been working with a few different energy management solutions - which also suggests that it doesn't come with the powerwall and management software is not included in the price.


Tesla aren't giving away much information!

Posted by Kristy on 2015-06-04 13:19:02 PM

Hi Daniel

I would assume that management for the battery would be at an extra cost because they haven't said that the powerwall definitely has it's own management system. Also I have read a few articles that say Tesla have been working with a few different energy management solutions - which also suggests that it doesn't come with the powerwall and management software is not included in the price.


Tesla aren't giving away much information!

Posted by Daniel on 2015-06-03 13:00:53 PM

Does the powerwall include a smart management system that decides when to charge or discharge the battery, dependant on peak times/power prices/consumption/solar generation? Or would this be an additional cost?

Posted by Kristy on 2015-05-10 20:53:09 PM

Hi Kevin

Thanks for your question. As far as I know Tesla haven't put out a expected life for these batteries. The expected life largely depends on the amount of cycles that battery goes through, so it could be quite variable.

They have given the units a warranty of 10 years, which the warranty length is normally a good indication of the minimum expected life. Tesla have said that the batteries in their roadsters will last a least 5 years, which may also be used as an indicator.

Hopefully we'll get an exact life expectancy from Tesla soon.

Posted by Kevin on 2015-05-09 17:00:27 PM

How long will they last?

Posted by Kristy on 2015-05-07 10:16:06 AM

Hi Ed

Sorry I am not sure when they will be available in NZ, but I do know that Vector in Auckland are the only ones that have a partnership with Tesla at this stage. So it sounds like Vector are lined up to receive the Tesla Powerwall, but I am not sure when.


Posted by Eddie on 2015-05-07 10:09:15 AM


When would it be available for purchase in Nz?


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