Inspirations and More Four Chairs Furniture and Design

energy storage is becoming more and more interesting to smart home owners and we recently spotted this write up of a Tesla Powerwall 2 installation on Michael Vorstermans Blog. A great account of the practicalities of installing the domestic battery, how it functions and the finances behind it. read on for all the details….

Late last year, Elon Musk surprised everyone by announcing a new version of Tesla’s less-than-a-year-old Powerwall home battery system, with double the capacity for the same dough.

The other players in this industry must have been gnashing their teeth, but bravely soldiered on with the expectation that “it’ll take them forever to deliver”.

Not so – my Powerwall2 was installed yesterday, one of the first in new South Wales, Australia – read on for the blow-by-blow and decide if you also want to be free from power blackouts and 3-figure power bills.

What is a Powerwall Anyway?

If you don’t yet know what a Powerwall2 is, read this section – if you do, skip to the next heading.

Simply put, it’s a slim, no-maintenance, weatherproof and near-silent rechargeable Lithium battery system with the front profile of a bar-fridge, located near your power board, paired with a Gateway box that manages power flows from and to your home and the battery system.

Inside it, there’s heaps of cylindrical battery cells, assembled into packs, which will also be used to power the upcoming model 3 electric car.

They are made in Tesla’s Nevada Gigafactory, and packaged inside a shiny white-painted steel enclosure, along with a charger, inverter, and water-cooling system.

The system has an installed cost of just over $10,700 in Sydney [Ed: currently £5,900 + installation in the UK] and you can get one with around a 2 month lead time today.

It’s designed to save the output of your solar power system during the day, so when the sun sets (when your solar generation falls away), it will power your entire house until it’s nearly discharged. And, if there’s a power blackout, the PW2 switches to powering your house from the battery instantly, so you still have power for your entire home until power gets restored, or the battery runs down.

It’s capable of supplying 13 kWhr, or so, of stored energy when fully charged, which for most homes will carry them through the night, and therefore saving you the cost of the power you would otherwise have to buy. The power level it can handle is 5kW Steady, 7kW Peak, enough to run most kitchen appliances, a split-system airconditioner, or even charge a short-range electric car (such as a Mitsubishi Outlander PHEV, which only draws 2KW to charge, taking 5 hours).

For me, with 4.8KW of paid-off solar on my roof, a rough calculation says the PW2 could pay for itself in 6 to 9 years, and it’s warranted for 10. If you don’t have solar power, it’s not for you, but given prices for power are only going to rise, you should consider getting solar cells anyway, if you own your home and have roof space available. I’ll go through the financial aspects in detail towards the end.

The install Process

I reserved a Powerwall2 via Tesla’s site in October last year – it’s a quick and painless process, pricing is entirely available online, it’s transparent and up front, so you have no need to chase around for quotes.

This is a significant advantage Tesla has, as there’s more than a few cowboys in this industry in Australia. Tesla’s checkout took a $500 deposit by credit card at order time, they followed up with several phone calls over the intervening months, a contractor (Downer EDI) did a site visit a few weeks before install, and then Tesla requested payment by bank transfer for the balance of the $10k this week.

7.00am: two tradie vans arrived promptly as promised, from a local solar outfit called Flash point Solar in Punchbowl. another guy from Downer also arrived to supervise. As it turns out, this was the first install for all of them.

The gear came in two large cardboard boxes – the Gateway, and the Powerwall2 itself. The PW2 weighs over 125kg (290 pounds says the sticker, but another one next to it says 67Kg, so clearly the whole “metric system adoption” in the us still has some bugs in it), with the result that a trolley is needed to shift it around. It is just wide enough to fit through a standard door.

8.00: Hardest part so far is figuring out where the wall studs are for the mounting bracket. My house has plastic cladding, so they can’t easily find the studs. .

The PW2 is expected to rest on the ground on feet, and the bracket is meant to prevent it from tipping over.

8.30: looks like they are working it out as they go – 5 guys here now – 3 from Downer, of which 2 were here just to learn, and they said they had done some training with a prototype.

9.00: Mounted, and then had to remove it.

They ended up putting a big piece of ply against the cladding to help spread the load (and give them more opportunities to bolt into the elusive frame studs). since they didn’t allow for the height of the PW2 bracket placement before bolting the ply to the wall, the ply ended up sticking out beyond the top of the PW2. The mounting bracket has a silver spring clip in the middle of the “T” that locks the frame to the PW2, and the clip can only be accessed with something very long and thin, like a spring-steel ruler. I made them a feeler to dismount it, (Tesla didn’t provide any tools with the PW2), and they pulled it off, and cut the ply down so it wasn’t visible.

9.15: apparently all the cables go in the side, to a junction box under the cooling radiator – this is a decent size one, like an inter-cooler from a car. They don’t need access to the back of the unit, although there is a wiring gland just visible there, for use with installations that require the cabling to pass through a wall. The black sides are plastic, and clip into place.

9.30: Gateway mounted, now they are discussing how to wire all the cables between the 3 boxes. There is an installer manual on an iPad, and a set of paper manuals, which are mostly safety advisories.

1.30: All cabling done. There is a clamp on the solar active input to measure it’s generation, and the gateway measures the house load from the power cable directly. The PW2 charges only from solar at the moment.

Tim from Tesla arrives to help the installer commission the unit. The Gateway has a built-in Neuros Wifi access point (TEGxxxx, username is installer’s email, password is SN#) and a Telstra 3G telco SIM, but the SIM has yet to be activated by Telstra, so Tim connects it to my home Wifi and uses a webpage to update the firmware. He says that the preferred connection method in future is via 3G so they do not need to rely on Wifi availability.

The installer used an iPad to connect to the PW2 Gateway’s AP, and defined the size of the solar inputs, identified my inverter model from a list, selected which measuring inputs in the Gateway are monitoring the load and generation, and entered my Tesla account login (you make this when you order, and there’s no ongoing costs involved).

At the end of this, the Gateway’s webpage showed the current state of the home current draw, solar generation, and charging status of the PW2. However, the power consumption figure for the home seemed too high for the few lights that were on, and closer examination of the metering setup in my powerboard showed that the solar net meter is summing the solar generation into the input to the home, so they end up running another clamp into the powerboard to measure the consumption load separately.

2.30: Done – I reckon they could shave off a couple of hours, now that they have the install experience, and if they had a brick wall to mount it on, instead of the foam pillows my house has.

To test the system, I turned on a TV that was visible from the powerboard, and then switched off the mains-input circuit breaker to simulate a power blackout – there was a slight clunking of relays in the Gateway, and the TV didn’t even flicker.

Tim said the switch-over takes only 30milliseconds, which should be fine for running PCs, and you do get a notification from the Tesla app on your phone that the house is now running on backup power. switched on the main circuit breaker again, and with some more clicks, the gateway changed over to the mains about 10 seconds later.

For solar installs here, local rules require any grid-connected solar system to shut down when the grid-power fails, to protect pole-and-wire workers. I expected this to apply with the PW2 as well, but, it doesn’t, and the solar system stays up when the grid goes down.

 

Tidbits

Other than the Tesla app, the only visible sign of the PW2’s operation is a LED light strip down the side of the unit that blinks when there’s a problem, is steady when nothing is happening, and pulses slowly when charging or discharging.

Monitoring: I’ve been monitoring the house load and solar generation via PVOutput for the last 6 years – this service provides a free portal to your house power flows via a webpage and phone app, once you install a small monitor in the powerbox.

There is no provision for PVOutput data from the PW2 yet – apparently it generates a huge amount of info, and Tesla are going to expose this at some time in the future, but, Tim said, they are focused on the app experience for now.

 

As only my dog is at home during workdays, my home’s generation was mostly exported up to now, and the majority of consumption occurred at night, so my home represents an ideal use case for the PW2. In the graph above, the green line is instant solar output, and the red one is instant consumption, with the shaded areas representing totals for each.

How long before you can get it: Apparently, there are installs booked here in the “thousands” range. Backlog for hardware is 2 months if you order now. Each team of installers could only do 1-2 installs per day, I reckon.

To some extent, the distributor you are chained to controls how soon the install will take place, due to the varying rules and equipment approval timeline processes they have, which are beyond Tesla’s control, so Tesla is prioritising the installs to customers chained to distributors that have the approvals ready now.

As usual, Elon is stepping on toes in this industry, by making it possible for us punters to reduce our dependence on the energy monopolies – they naturally will do whatever they can to limit the uptake of residential battery storage.

AC vs DC: Whilst Tesla initially talked about both DC- and AC-charged Powerwalls being available, they settled on only doing the AC-charged ones – Tim says this eliminated any issues that might arise from varying DC capabilities of the many different solar arrays used worldwide, since the AC output from an existing solar inverter is fairly standard by comparison. Yes, there’s some losses in converting the AC power to DC in the battery, and back again, but it meant a shorter time to market, simplified certification, better control of the charging process, lower prices due to scaling of one type only, and no requirement for the PW2 installers to have to muck around with rewiring existing solar cabling setups.

Commissioning: enabling it on the day of install depends on the customer’s energy distributor’s regulations. There is a switch on the battery, and another inside the Gateway to bypass the system.

I’m with Endeavour NSW, who are happy to have the sparkys sign off on it, whereas some other distributors insist on L2-certified inspectors, and such to commission it. Apparently, Endeavour are also fine with up to 10KW of solar on a single-phase home.

Overloads: I asked what would happen if the house current draw exceeded the power output of the PW2 – Tim said the output voltage will begin to drop, and then the unit would reset, to shed the loads and give you an opportunity to switch off whatever is drawing too much – this would be the same scenario as when I popped a circuit breaker last week, as there was a car charging+dishwasher+microwave+column heater all on at the same time, and the load went over 8KW.

Acoustics: it makes the occasional faint “tick”, and a low-pitch whirring sound when the fan runs. You’ll only hear these if you sit right next to it. The fan blows air out the top-right corner, opposite the radiator. It’s quieter than the solar inverter, which always makes a ticking-buzz noise.

Theft: Some people mentioned worrying about the unit being knocked-off, since it’s not behind a locked door. I don’t have any way to put it behind one at my home (no garage), but since it weighs 130Kg, random junkies are not going to be strong enough to lift it, and they would need a tow-truck to yank it off the wall, because of the fiddly clip.

Given Tesla’s no-advertising policy, I imagine the vast majority of people here would have no idea what this mystery white box on my wall does, or what it’s worth. And, I have a backup security system just in case…

The Tesla Phone app

You can download Tesla’s free Android or iphone app to manage your Tesla cars and Powerwalls. My Tesla app did not have any registered devices in the day after install, and Tim said, at the time, that someone in Tesla USA would need to tick a box. I chased up the Tesla email contact I had for the payment process, and he called back an hour later to say it was done (on a Saturday morning, as well).

Basically, it lets you know if all is well with the system, by monitoring the state of power flows and battery charge state. Herewith some screenshots:

This is the home page you get after signing in. It takes about 5 seconds to fetch the current state when you open the app, and gives a quick glance to see what the battery is doing and how full it is. In this shot, mine is almost discharged, and very little power was used from my solar