Tesla Powerwall 2 Review

[Barney12]

Good review of the Powerwall 2 here. The ROI aspects obviously need taking with a large dose of salt as the install is in Australia! However, some interesting info:

 

http://www.automatedhome.co.uk/carbon-footprint/tesla-powerwall-2-domestic-solar-battery-installation-photos-details.html

[jack]

Makes even more sense in Australia given the high levels of insolation compared to the UK. From memory you generate something like 50%+ more per annum for a given installation somewhere like Sydney.

 

Interestingly, one of the biggest power drains is air conditioning. Since it's generally sunny when it's hot, load matching is a lot better than in the UK, where we need little cooling in summer but (for the average house) a lot of heat in winter.

 

We paid something like £600 for our utilities last year.  I guess I could get that below £500 with only minor tweaking and lifestyle changes. For a low energy house, the payback just doesn't make economic sense at the moment.  Maybe in a few years when the price falls a further 50%...

[SteamyTea]

22 hours ago, jack said:

Interestingly, one of the biggest power drains is air conditioning. Since it's generally sunny when it's hot, load matching is a lot better than in the UK, where we need little cooling in summer but (for the average house) a lot of heat in winter.

Too true.

 

What a small amount of storage can do is help the national grid by smoothing out spikes.  Think mornings with electric showers and kettles boiling.

If a home runs a 10 kW shower for 20 minutes (more education needed) that is 3.3 kWh, if 10 million homes had 4 kWh of storage that was dedicated to that task, then we could defer that 4 GWh load.

Now I have know idea what people pay to have an electric shower fitted as it is a relatively cheap part of a bathroom refurbishment.  At the moment the cost of battery storage is prohibitive, but if the cost can be reduced to £1000 (highly unlikely for the foreseeable future), then it would become viable.

One way to incentivise would be time sensitive electricity pricing, say 70p/kWh between 6:30 AM and 8:00 AM.  This would make the daily shower cost £2.31, compared to 40p.

Over a year that would be a price difference of around £700.

Trouble is that at £700 a year, a simple vented storage cylinder and pumped shower would be cheaper to install and run (size may be an issue).  Or maybe an Sunamp.

 

I think than rather thinking of payback times, comparing it to alternatives is a better idea.

Edited June 21, 2017 by SteamyTea

[Jeremy Harris]

I've long thought that a system like the one they have in parts of France, where EDF change the tariff when they predict high demand, would make sense.  Over there, or at least where some friends used to live down in the Loire valley, they announce the high price times and dates on the news, so that people can plan ahead and not use high power appliances during the times that the tariff is high.

 

It's pretty low tech, doesn't require any changes to meters, cabling, data collection, etc, all it needs is for the billing software to take account of the high rate periods.  I like the fact that it's nice and simple, with little to go wrong, be hacked etc, and seems a better solution than fitting smart meters, that so far seem not to be very smart at all.

 

The great thing about it is that it effectively transfers part of the demand management task from the energy company to their customer, raising awareness of the challenges of managing peaks and troughs in demand.

 

On the battery topic, I think there's also some value in the power cut supply capability that the Tesla system has.  I'm looking at buying a small generator and fitting a changeover switch and connection point, so that I can run some of the house loads when we get a power cut (a not uncommon occurrence here).  To me, paying up to around £500 to £600 for a solution to reduce the impact of a power cut would be worthwhile, and I might consider paying a bit more for a solution that provided a few hours of full power capability in a power cut.  The Tesla Powerwall 2 would run our house for more than 24 hours, with no load shedding and pretty much no restrictions, just a bit of peak load management when cooking.

 

It's not enough to make the Powerwall 2 viable, in terms of overall cost saving, but it does make it look more attractive.  We generate massively more than the house uses for a large part of the year, and a few rough calculations suggest we could shave around £200 to £250 from a no standing charge electricity bill by having battery storage.  We might be able to shave a bit more off if there was a reasonably cheap E7 tariff, if there's a way to grid charge the Powerwall 2 overnight in winter.  It looks like we could save perhaps £2000 to £2500 over the life of the battery pack in the Powerwall 2, so not enough to make it worth fitting yet.

Edited June 21, 2017 by JSHarris

[Barney12]

1 hour ago, JSHarris said:

On the battery topic, I think there's also some value in the power cut supply capability that the Tesla system has.  I'm looking at buying a small generator and fitting a changeover switch and connection point, so that I can run some of the house loads when we get a power cut (a not uncommon occurrence here).  To me, paying up to around £500 to £600 for a solution to reduce the impact of a power cut would be worthwhile, and I might consider paying a bit more for a solution that provided a few hours of full power capability in a power cut.  The Tesla Powerwall 2 would run our house for more than 24 hours, with no load shedding and pretty much no restrictions, just a bit of peak load management when cooking.

 

 

I must admit is was that part of the review that spiked my interest. We get a lot (and I mean at least 3-4 times a month) of power cuts. Often they are just for a matter of seconds but it's a right royal pain the bum. In today's modern world everything resets and takes several minutes to "come back up". It surely most shorten the life of things like; routers, NAS, PC's, Sky Boxes, TV Boxes etc etc. 

 

I know we could fit a generator but that's a big messy, maintenance heavy solution which also provides no benefit in short outages.

[Jeremy Harris]

My solution to dealing with network connectivity was to build a battery-backed, uninterruptible, low voltage power supply box for all the network kit.  This provides both 12V and 5V regulated DC supplies, and has a 100Ah, ex-server farm UPS, sealed battery.  It works well, and means that both the LAN and internet connectivity remain working during shorter power cuts.  If the power cut is more than a couple of hours the internet connectivity goes down, presumably because the back up battery in the fibre cabinet up the road runs down.

 

It would be be a lot neater to have a whole house backup supply, one that switches over in a few ms, as the Powerwall 2 does, though.

Edited June 21, 2017 by JSHarris

[Barney12]

On 6/21/2017 at 08:32, JSHarris said:

On the battery topic, I think there's also some value in the power cut supply capability that the Tesla system has.  I'm looking at buying a small generator and fitting a changeover switch and connection point, so that I can run some of the house loads when we get a power cut (a not uncommon occurrence here).  To me, paying up to around £500 to £600 for a solution to reduce the impact of a power cut would be worthwhile, and I might consider paying a bit more for a solution that provided a few hours of full power capability in a power cut.  The Tesla Powerwall 2 would run our house for more than 24 hours, with no load shedding and pretty much no restrictions, just a bit of peak load management when cooking.

 

Just to update this thread on the point regarding powercut backup. I've discovered that although the PW does have the capability it is NOT enabled for the UK market as the grid wont allow it. Apparently Tesla are looking to get the required approvals to make it possible but nothing yet.

 

They are also working on a firmware update which would allow off peak charging of the battery from the grid.

[DenkiJidousha]

The update to allow off peak charging has apparently been released, no news on UK support for power during a grid outage.