Tesla Powerwall 2 Owners

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SQLGeek

135 posts

Master Geek

#225973 13-Dec-2017 16:03

I have just ordered and paid a deposit for a Tesla Powerwall 2, I would been keen to hear from other NZ owners.

Telsa are sending someone round to do a quote in January. It is expected to cost $13K to $14K installed. The deposit is refundable.

My place in Christchurch has a PV system with 15 x 270 Watt panels with Enphase M215 micro inverters. I have 3 phase power, so there is only 5 panels per phase. I often export on 2 phases and import on the other! This makes my system very inefficient, hopefully the battery will help with this.

Like most people I really only have excess supply in the summer. The aim is to top up the battery with cheaper night-rate power at other times.

Solar without a battery you are limited to power retailers who support buy-back. Once the battery is installed I can look to switch to a retailer like Flick which should help reduce my bill even further.

How have you found your Powerwall? Any tips? What was the impact to your monthly bill?

TIA

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2074 posts

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#1919153 13-Dec-2017 16:12

I don't have a PW2 but am very interested in getting one potentially. I am in ChCh as well and have 3.2kW of panels (into a Enasolar grid-tied inverter). I am only single phase and have a diverter setup to heat up my HWC with any excess, but in summer the cylinder gets up to 80 degrees pretty quickly and then I am exporting most of my PV.

I wouldn't have any excess solar available in winter to top up my battery but I am interested to know if they can be charged using cheaper night rates - I didn't think they supported that yet? That would be a clincher for me if they could do that. Charge them up overnight in winter and use during the day. And in summer charge via solar during the day and use in the evenings before 9pm.

Will be watching this thread with great interest!

zenourn

271 posts

Ultimate Geek

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#1919309 13-Dec-2017 20:57

I also don't have a powerwall but am interested in how they are looking at setting it up with your 3-phase power, which we also have.

From my understanding you can configure the gateway to monitor all three phases and when getting solar input it will cover load on all three phases with any remaining surplus going to the PW2. However, the PW2 can only actually supply load/backup for a single phase. I don't see this as a big limitation as can be intelligent about how loads are split between the phases.

I think the real advantage of the PW2 is being able to have power (via solar and PW2) during a power outage. Living rural we pump our own water, have a mini water treatment plant, etc, so without power everything shuts down. Also have an electric vehicle so a PW2 gives advantage that can still charge it during outages. Always remember earthquakes when were without power for over 4 weeks...

PhantomNVD

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#1919335 13-Dec-2017 22:48

While I’d love one of these, I’m personally awaiting the launch of an EVSA that allows dual direction sharing of the 24KW battery my Leaf already has... charge up during the night and use excess ‘mileage’ each evening to power through the peak times! When I already have 24KWh of batteries, why buy another set? \_o_/

Zeon

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#1919343 14-Dec-2017 00:20

Are these DC or do they have an inbuilt inverter? If DC do you know what input/output voltage? Looking at options for DC only....

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Aredwood

3885 posts

Uber Geek

#1919347 14-Dec-2017 01:24

@SQLGeek I have been told by Flick that they will be allowing solar customers to sign up early in the new year. And also that Flick will pay you the wholesale rate for the power that you export. So could be worth waiting for Flick to start offering solar first, and see how it goes with them.

Also have you done an energy audit on your house to identify which load is the one that always causes the 3rd phase to always be importing? And whether it would be possible to rearrange the loads across the phases to improve the balance?

If the load that is causing the importing is a hot water cylinder, Consider getting solar hot water installed instead. And if that load is an electric stove - get a gas stove.

Lots of electric cars support 3 phase charging, so consider just buying an EV and enjoy the fact that you are lucky enough to have 3 phase connected. I want to get 3 phase for my own house. But Vector (my lines company) would probably ask for big $$$ to upgrade their street cables before they will let me get it. And that is in addition to the costs of an underground mains cable and switchboard upgrade.

epr

260 posts

Ultimate Geek

#1919349 14-Dec-2017 05:38

Really interested in this topic as I just installed 6 300 watt panels with enphase inverters with enough workspace for probably up to 4 more that I would probably get if I ever got a battery system and interested in others experiences I am in Christchurch.

kryptonjohn

2523 posts

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#1919379 14-Dec-2017 08:33

What's the efficiency of charging/draining the battery like? My gut feel is that the losses from AC-DC and DC-AC conversion plus any battery losses(?) would outweigh the off peak saving?

The cost of the panels, battery and setup still look too high to save money with solar? (unless there are subsidies - which to me means working hard working kiwi wage earners paying taxes to support well-off early adopters).

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zenourn

271 posts

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#1919383 14-Dec-2017 08:43

kryptonjohn:

What's the efficiency of charging/draining the battery like? My gut feel is that the losses from AC-DC and DC-AC conversion plus any battery losses(?) would outweigh the off peak saving?

The cost of the panels, battery and setup still look too high to save money with solar? (unless there are subsidies - which to me means working hard working kiwi wage earners paying taxes to support well-off early adopters).

About 90% round trip efficiency is what is claimed by Tesla (panels to PW2 is DC to DC, PW2 to load is DC to AC).

I've measured the efficiency of our electric car charging (AC to DC to charge then compared to kWh actually added to battery) and am seeing 80% efficiency. So Tesla have either done a really good job or numbers aren't quite reality.

Yes, the return on investment for solar and PW2 based upon my calculations is rather negative even with the high usage we have (50 kWh+/day). It does effectively provide a backup power source though.

kryptonjohn

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#1919384 14-Dec-2017 08:47

zenourn:

kryptonjohn:

What's the efficiency of charging/draining the battery like? My gut feel is that the losses from AC-DC and DC-AC conversion plus any battery losses(?) would outweigh the off peak saving?

The cost of the panels, battery and setup still look too high to save money with solar? (unless there are subsidies - which to me means working hard working kiwi wage earners paying taxes to support well-off early adopters).

About 90% round trip efficiency is what is claimed by Tesla (panels to PW2 is DC to DC, PW2 to load is DC to AC).

I've measured the efficiency of our electric car charging (AC to DC to charge then compared to kWh actually added to battery) and am seeing 80% efficiency. So Tesla have either done a really good job or numbers aren't quite reality.

Yes, the return on investment for solar and PW2 based upon my calculations is rather negative even with the high usage we have (50 kWh+/day). It does effectively provide a backup power source though.

That's better than I expected. Hopefully the efficiency of the panels will keep improving and the price will keep dropping.

Aredwood

3885 posts

Uber Geek

#1919456 14-Dec-2017 10:43

zenourn:
About 90% round trip efficiency is what is claimed by Tesla (panels to PW2 is DC to DC, PW2 to load is DC to AC).

I've measured the efficiency of our electric car charging (AC to DC to charge then compared to kWh actually added to battery) and am seeing 80% efficiency. So Tesla have either done a really good job or numbers aren't quite reality.

Yes, the return on investment for solar and PW2 based upon my calculations is rather negative even with the high usage we have (50 kWh+/day). It does effectively provide a backup power source though.

Make sure that you also allow for wear on the battery due to constant charge and discharge cycles. This cost is often the most expensive part of owning a battery system.

zenourn

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#1919884 14-Dec-2017 21:28

Aredwood:

Make sure that you also allow for wear on the battery due to constant charge and discharge cycles. This cost is often the most expensive part of owning a battery system.

Yes, definitely. Tesla offer a ten-year warranty which includes that when used for "solar self-consumption/backup only" that the battery will still offer 70% of it's original capacity when 10 years old with no limit on the number of cycles.

I'm doing analysis on battery health in electric cars. The batteries in Tesla's cars seem to be holding up really well. Their active thermal management, which is also present in the PW2, is beneficial. In general I'm seeing that age (and temperature) is the major factor rather than number of cycles for the chemistry used in cars. Is likely similar for the PW2.

I don't think people are getting battery systems for the economics, more the other benefits they provide such as backup power and problems with solar and unbalanced 3-phase. Under generous assumptions (14kWh into PW2 from solar and used *every* day for 10 years, no capacity loss, 5% interest on capital, depreciation over 10 years, opportunity loss of reselling to grid at $0.07/kWh...) you've effectively paying $0.45/kWh for the power from the PW2.

[edited: half a paragraph disappeared when posted!]

Aredwood

3885 posts

Uber Geek

#1919940 14-Dec-2017 23:49

In relation to the unbalanced 3 phase issue. I hope that the solar installers checked that the property actually has 3 phase connected. I have come across a property that was originally setup for 3 phase. But looking at the power pole that feeds the property - the 3 phases have all been connected in parallel, and there is only single phase on the power pole. The network didn't care that the neutral to that customers property will now be running at 3x it's designed loading.

Property is in a dense bush area - so presumably the network got sick of complaints about voltage issues due to tree branches breaking the neutral.

Also if the smart meter happens to be the EDMI Mk10D, That meter has a setting for how to treat a simultaneous import / export situation. It can either nett the phases together, or treat them separately.

It could be worthwhile contacting some different retailers and metering companies. As there is a chance that some of them might use nett phase mode for import / export calculations. As Im not aware of any rule that specifies which setting should be used.

If the meter can be reprogrammed to use nett phase mode - that would be by far the easiest and best way to solve the multi phase export / import issue.

Linuxluver

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#1919946 15-Dec-2017 00:35

SQLGeek:

I have just ordered and paid a deposit for a Tesla Powerwall 2, I would been keen to hear from other NZ owners.

Following. I want to go this route as soon as I can get it organised.

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desultory

6 posts

Wannabe Geek

#1919969 15-Dec-2017 07:48

Another good option / alternative to the PW2 (for people who don't want to have the long wait time, or who want more expansion options to further easily expand their battery capacity) is this 14.4kW Retrofit system here

https://www.hiteksolar.co.nz/products/14-4kwh-retrofit-solar-hybrid-storage-add-on-system

It can be upgraded to 28.8kW also just by bolting on a second battery set to the same inverter (one of my friends down CHCH runs the 28.8kW version and he has 2 nissan leaf cars that he charges up from solar + his stored energy and it works great for him).

It's using long life lead carbon battery storage rather than lithium like the PW2 does, so yeah about 10-12 years of good usable battery life also and with a cheap battery replacement cost (half price) at the 10-14 year period if / when you need another set.

Also for people who are off-grid and want to upgrade their existing battery storage (or add more) you can purchase the lead carbon battery storage separately (ie without the inverter / kit), where as that's not an option for current off-grid clients to buy the PW2 for dedicated off-grid system use (it's made as an on-grid storage battery only).

I run one of these systems at my own house and it runs great. I pay the power company $150 for my yearly bill, and they pay me $200 for exports to the grid + the $600 TECT cheque, and now I've just been given the option to also supply upto 5 friends 50kW units per month (each) making 250kW units per month total where they can buy my excess Power from me at whatever rate they want (7c seems fair seeing that's all most retailers pay anyhow) so that means for those friends instead of buying at 50kW each month at 32-34c they now get it at 7c which is awesome (I'd rather friends get it at that, than be forced just giving to the power company at that price while friends are stuck paying retail for that same power).

Any questions please let me know thanks.

SQLGeek

135 posts

Master Geek

#1920047 15-Dec-2017 10:09

Aredwood:

In relation to the unbalanced 3 phase issue. I hope that the solar installers checked that the property actually has 3 phase connected. I have come across a property that was originally setup for 3 phase. But looking at the power pole that feeds the property - the 3 phases have all been connected in parallel, and there is only single phase on the power pole. The network didn't care that the neutral to that customers property will now be running at 3x it's designed loading.

Property is in a dense bush area - so presumably the network got sick of complaints about voltage issues due to tree branches breaking the neutral.

Also if the smart meter happens to be the EDMI Mk10D, That meter has a setting for how to treat a simultaneous import / export situation. It can either nett the phases together, or treat them separately.

It could be worthwhile contacting some different retailers and metering companies. As there is a chance that some of them might use nett phase mode for import / export calculations. As Im not aware of any rule that specifies which setting should be used.

If the meter can be reprogrammed to use nett phase mode - that would be by far the easiest and best way to solve the multi phase export / import issue.

Defiantly 3 phase, the house was an Earthquake rebuild so is only 2 years old.

The load is quite well spread over the 3 phases, the main problem is the spa pool, it draws more than 5 panels produce even on the sunniest day. I have gas hot water so that’s not a factor.

I’m with Ecotricity on their spot price plan. They only buy from renewable sources so it’s probably a tad higher than Flick. They don’t have an iPhone app and their website is terrible, I have to login and can’t bookmark the page with the current price, useless!

Here’s my November export and an example day. The spa comes on at 3:45am and again at 11am. I chose these times as it should be cheap and night and I should be generating solar at 11am.

I’ll investigate the nett phase mode of the meter, this could be a good solution. Thanks for the suggestion.

From what I’ve read from Australian owners firmware v2.0 is going to support topping from night-rate power. Telsa recently released v1.9 so everyone is hoping it’s not too far away.

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