Speak EV - Electric Car Forums banner

1 - 20 of 26 Posts

·
Registered
Joined
·
149 Posts
Discussion Starter #1
Has anyone tried using the Tesla Powerwall storage battery to store the solar energy on using for home charging. I have read in an article one of the customer from wales was the first to use Powerwall1 for home usage but not for EV charging.

I have had a discussion with Solarplants (a Solar provider) and the max energy can be harnessed would be around 6.5 Kw for Powerwall1. But for Powerwall2 this could go to 14 Kw (as powerwall2 would be available in the UK during first quarter of 2017).

As the home charger has max power of 7.4 Kw connected to Grid at the moment, If the combination of Solar Plus Grid would really help to bring the cost of electricity down than the current energy prices, as I would like to explore this.

Any views or thoughts on this would be much useful to explore OR Anyone had any sort of information on solar providers who does this type of installation.
 

·
Registered
Joined
·
18 Posts
Hi Anto. Yes, this is indeed possible. As soon as I get hold of my MS I'll be doing just that...well, when there's enough solar generation to do so anyway! Have a Powerwall 1 DC coupled with a 3.6kW inverter.

As well as the capacity, there's also the power output of the battery to consider, as well as how that is delivered - via a single inverter for on site generation or separate inverter each for battery and generation.

Powerwall currently has power limit of 3.3kW constant. With my installation I can charge up to 3.6kW for "free" (until the battery empties) if there's solar over 300W too.

Without going into more explanation for now (though happy to do so if you're interested! There are just a fair few considerations...), it can help keep bills low, particularly if you limit charge to something lower...unless you need charged more quickly. It is only fairly low capacity (for ev charging), so charging at night will only ever save you less than the 6.4kW capacity..

Powerwall 2 will help...

A subject of great interest to me, too!
 

·
Registered
Joined
·
612 Posts
I have my Powerwall1 set up so it explicitly does not charge the car - I use E7 for that, and the Powerwall is best used to replace expensive daytime grid power.
The Powerwall is set so it never discharges below 20% (don't want it empty all winter), and doesn't discharge at all between 00:30 and 07:30 GMT. My car takes between 8 and 35 kWh per night to recharge it, so the Powerwall wouldn't make much impact on that even it were used.
 

·
Registered
Joined
·
612 Posts
@bryand I was not aware that it was possible to alter parameters on the Powerwall. Was this done by the installation contractor or is there some interface to a computer or phone app so it can be changed by the user ?.
It was done by the installation contractor, whose SolarEdge portal has a lot more tabs to it than ours does (I just get 'Dashboard' and 'Layout'). They don't trust us to fiddle with it ourselves!
 

·
Registered
Joined
·
18 Posts
yes, powerwall is very configurable via SolarEdge so that you can set it up for needs, exactly like above. What it will do nicely is grab as much solar as possible so you can use it how you want. That market leading power input and output really helps.
 

·
Registered
Joined
·
1,220 Posts
I have panels but no storage facility yet. I am about to get an Economy 7 meter though, and since I am an Ebico customer I pay no standing charge (though kwh rate is higher).

Currently my meter is going backwards but I am monitoring it, keeping it under my previous billed reading, and so using my "free" power until my meter gets changed....

E7 should let me charge the car for about £4.50 overnight...
 

·
Registered
Joined
·
85 Posts
I think this is a great idea and love the idea of running my house and car from my own solar, but not sure it is cost justifiable yet.

I would need 2 x Powerwall 2.0's plus the panels to charge them and would put about 15 - 20 KWh back in to the car each night. The remainder would run the house. I would also benefit from daytime usage as I often work from home so my usage is pretty constant around the clock.

I am waiting to see what deals are available when these new Powerwall's are out in the wild for real.
 

·
Registered
Joined
·
193 Posts
Coupled with an immersion heater diverter these new power walls could work well with a much bigger pv system. I would be tempted to put on 8 kwh or 12 kwh on multiple facing roofs. Cost would not go up in proportion to kwh. And not qualifying for fit is not really a problem with the amount they're offering now anyway
 

·
Registered
Joined
·
18 Posts
Definitely a good call there. More consumption and storage requirement means more solar generation requirement. Barring grid connection limits (a pain generally, but less-so with storage) there's no reason not to go to said decent sizes to really get the most out if the whole set up.

FIT (although small) is still payable on these sizes of systems...unless it's an extension to existing system.

More storage gives more flexibility make best use of E7 or other time dependant billing likely to be implemented with smart metering too.

It's just a case of the cost being right...Powerwall 2 available early next year I understand.
 

·
Registered
Joined
·
612 Posts
... I would need 2 x Powerwall 2.0's plus the panels to charge them and would put about 15 - 20 KWh back in to the car each night. The remainder would run the house...
Make sure you do your sums for the worst-case scenario. If you need 20 kWh a night to charge the car every night all year round you will need a lot more than 20 kW of panels.
 

·
Registered
Joined
·
1,495 Posts

·
Registered
Joined
·
1,524 Posts
Indeed - here is my actual 4kw generation since installed in Aug 2011 in the South east
upload_2016-11-29_12-29-53.png

on 3 days (5/2/12; 20/1/13; 21/1/13) there was no generation at all due to heavy snow on the panels
upload_2016-11-29_12-32-3.png

In these graphs the grey bar/line represents the government forecast averages on which the purchase was based & which you can see for yourselves proved to be quite pessimistic in almost every month every year
 

·
Registered
Joined
·
18 Posts
Very nice. And it's really common to exceed generation estimates - either the mandatory ones or the very good estimates from PVGIS above.

It's almost definitely not cost effective installing enough capacity to provide the required energy all year round as there are a few practical reasons for it getting a bit more costly. Besides, there would also bee too much energy in the summer. Diversion to heat (secondary to batteries) is good, but of course far less of it is required in the summer.

The main issue with this technology is that it's so site specific. It really depends on the load and generation patterns to decide if it's worth it, and if so what equipment to use to make it work as well as possible. EG GaryB above working from home - would need a system large enough to reliably feed the daytime loads as well as to charge the battery bank. It's all good though even in times of not enough excess, as natural self consumption is still offsetting daytime electricity cost.
 

·
Registered
Joined
·
2,398 Posts
I have my Powerwall1 set up so it explicitly does not charge the car - I use E7 for that, and the Powerwall is best used to replace expensive daytime grid power.
The Powerwall is set so it never discharges below 20% (don't want it empty all winter), and doesn't discharge at all between 00:30 and 07:30 GMT. My car takes between 8 and 35 kWh per night to recharge it, so the Powerwall wouldn't make much impact on that even it were used.
Can you charge your Powerwall up from Economy 7 at times of the year when not enough solar to fully charge it? Have wondered about the economics of charging a Powerwall by night then using it in the day. Wonder what the return on investment would be? Probably something like

Powerwall cost = 13p kwh (x)

Where x is the number of kWh needed to equal the Powerwall price?
 

·
Registered
Joined
·
2,398 Posts
Yes, it is possible. I've never done the sums though! I keep meaning to...but it's complicated when paired with solar!
I make it 2,750 charges to re-pay the investment, based on the savings from using E7 electricity stored during the non-7 times.

If you managed to do this daily the Powerwall 2 would pay for itself in 8 years approx.

This does not take into account the transmission losses etc.

It also does not factor the solar energy.

On the face of it, if you have Economy 7 then even without solar the Powerwall 2 can pay for itself as soon as solar - without any fit.

Am I missing anything obvious / getting it wrong?
 

·
Registered
Joined
·
18 Posts
It depends on lots, including the installed cost and the rates for peak and off peak you use. You also need to consume all of the energy charged into the battery too - no use charging the full capacity for it not to be used (until the next off peak). With solar there will be some of the year it's best to use solar to charge for "free"...but then the transition from solar to off peak is complicated - too much off peak charged overnight means no space for "free" solar charging during the day and you'll end up exporting the solar generation at the cost of the "wasted" off peak cost from charging.

I expect electricity tariffs will change format over the coming years too. Likely in a way which will benefit those of us with storage too.

But yes, I totally agree with your sentiment - there's almost certainly a place for storage with or without renewables over the coming years.

AC Coupled Powerwall 2 will vastly simplify this process too in this scale of system, which is nice, as it has its own inverter. This will hopefully keep the installed cost down, which is quite high for the Powerwall 1 (depending on set up).
 

·
Registered
Joined
·
612 Posts
Can you charge your Powerwall up from Economy 7 at times of the year when not enough solar to fully charge it?
No you can't. The way the Powerwall is wired into the DC side of the system you would need a hefty charger to charge up the Powerwall from the grid, and then when it discharged, you would be earning FiT on the E7 electricity and there is no way the power companies would allow that.
 

·
Registered
Joined
·
18 Posts
It is possible to charge DC coupled from the grid with SolarEdge standard equipment.

Your second point on metering is the stumbling block though. I must find it if there is an approved and sensible way around this... The obvious way would be to use a bidirectional meter in place of standard fit meter and subtract one from the other to get Feed in tariff value.
 
1 - 20 of 26 Posts
Top