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What do you do with your excess solar power?

Wol747

Member
Aug 26, 2017
978
451
Tea Gardens
FWIW (I'm in Australia so sunshine ain't a problem!):
My panels generate about 18 - 20 KWh/day, no battery. I set the car to start charging at 10.00 and at a low amperage so that most if not all the electrons come from the roof and not the grid. I pay 25c per KWh from the grid and receive 9c per KWh for any excess that goes back to the grid.
My retirement community (278 homes) is currently being sized up for a company to install a Community Embedded Electricity Network - they put panels on all the common buildings such as restaurant, clubhouses, bowls rinks etc and a 1MWh battery, all at no cost to us - and charge us 20c KWh for our usage from their "grid" and pay 15c KWh for any surplus each house generates.
I looks like a great deal and shows that all the misinformation about "all the land will be overrun with solar panels" is so much BS - there are millions of sq. m of roofs just waiting to be used for generation, everywhere.
 

KendoNagasaki

Member
Oct 30, 2019
68
34
Edinburgh
No, not lucky enough to have a feed in tariff. That would be great..

Yes 27 kWh isn’t that much to export, but it’s frustrating that I’ve actually imported / purchased almost 100 kWh in the same time. Albeit at off peak rates.

But still…

That’s my 27 kWh of electricity. I made it!

I will admit to being tempted to put the kettle on for a cup of tea, but I draw the line at using the tumble dryer on sunny days. The laundry has to go on the line.
Last I checked, my export tariff on OVO is 5.5p per kWh vs 5p per kWh on Octopus Go to fill the car during the night.

honestly, other than basic things like aiming to run the laundry or dishwasher mid afternoon, and trying to have only one on at a time, I don’t worry too much about using all the generated electricity.

biggest gain is in making sure you don’t exceed what you are generating during the day.
 

RedMod3

Member
Oct 21, 2020
131
97
Hampshire, UK
We are all electric with heat pumps for heating in winter and cooling in summer. Steady state power consumption is 1.2kW ( we have a lot of IT running). The 16 panels we have produce a peak of 3.6kW, and we use a solar diverter to automatically send surplus power to our electric heater in the water cylinder. It is rare for us to export any power to the grid. As we have E7, out Tesla and Smart car are only charged at E7 rates (8p) at night.
 
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browellm

Member
Oct 4, 2019
501
447
Notts
My agile export is now live, so when I do have a bit of export available I actually get some tidy rates, especially around that 4pm spring/summer time when the battery is already full.
 

Llama.

Member
Jan 25, 2021
179
88
Leeds, UK
My agile export is now live, so when I do have a bit of export available I actually get some tidy rates, especially around that 4pm spring/summer time when the battery is already full.
Do you discharge your battery into the grid when the Agile rates are good?
 

browellm

Member
Oct 4, 2019
501
447
Notts
Do you discharge your battery into the grid when the Agile rates are good?
I don't plan to aggressively because I can consume most of what I produce. Although I can get 14/15p at peak times you also have to consider round trip efficiency means the real figure is less.

It's just handy to know that the few kW of overage I sometimes have is softening the iffy import rates that Agile has right now and works a lot better than the flat 5.5p export tariffs.
 
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Peter 224

Member
May 9, 2021
185
137
Salisbury
I've got a November 2011 4kwh set of panels that are on the old, high, FIT, the revenue last year was £2200, tax free. I have a Solar Boost gizmo that turns on the immersion heater if we are not using all our generated power and a 3kwh battery as a soak. But now I have a 77kwh battery in the Tesla and I'm researching the possibility of allowing the grid to take power from the car and put it back when power is cheap.
The claims are tempting, as are the reported Government Subsidies, but I do wonder if it is really possible and even if it is, what are the downsides?
One that springs to mind is shortening the battery life through repeated charge/discharge cycles.

Has anyone here gone down this route?
 

Cardo

Member
Sep 22, 2020
444
300
Surrey, UK
I've got a November 2011 4kwh set of panels that are on the old, high, FIT, the revenue last year was £2200, tax free. I have a Solar Boost gizmo that turns on the immersion heater if we are not using all our generated power and a 3kwh battery as a soak. But now I have a 77kwh battery in the Tesla and I'm researching the possibility of allowing the grid to take power from the car and put it back when power is cheap.
The claims are tempting, as are the reported Government Subsidies, but I do wonder if it is really possible and even if it is, what are the downsides?
One that springs to mind is shortening the battery life through repeated charge/discharge cycles.

Has anyone here gone down this route?
Current Teslas don‘t support V2G, so you’re going to struggle with this idea. Elon has previously said he’s not a fan of this. Currently, the only vehicles that support true V2G (without using a 3 pin socket) are Chademo equipped vehicles, and I think the Leaf is the only one that actually supports it.
 

Dilly

Active Member
Feb 24, 2020
1,871
1,534
Norfolk
I've got a November 2011 4kwh set of panels that are on the old, high, FIT, the revenue last year was £2200, tax free. I have a Solar Boost gizmo that turns on the immersion heater if we are not using all our generated power and a 3kwh battery as a soak. But now I have a 77kwh battery in the Tesla and I'm researching the possibility of allowing the grid to take power from the car and put it back when power is cheap.
The claims are tempting, as are the reported Government Subsidies, but I do wonder if it is really possible and even if it is, what are the downsides?
One that springs to mind is shortening the battery life through repeated charge/discharge cycles.

Has anyone here gone down this route?
I’ve got 2 Tesla Powerwalls. There is tariff which will draw from the PW’s and pay the same rate as I would pay to draw from the grid. About 8p/Kwh.
It’s not for me though.
The PW’s store 27Kwh of power. More than enough to run the house and heat water when the sun’s gone down. I can also use some to charge either car.
inevitably I export some!
 

Peter 224

Member
May 9, 2021
185
137
Salisbury
Current Teslas don‘t support V2G, so you’re going to struggle with this idea. Elon has previously said he’s not a fan of this. Currently, the only vehicles that support true V2G (without using a 3 pin socket) are Chademo equipped vehicles, and I think the Leaf is the only one that actually supports it.
Cardo, thanks for this information: if Tesla doesn't support V2G then the idea seems a blind alley. Once again, it seems, a sales person was making unsupported claims to try and sell something....
I have a python tech 3kwh battery and have looked at adding to that, but the ROE doesn't make any sense. At. the moment on a sunny day I get 24 to 25kwh per day and to properly make use of all that I'd need to be able to store about 22kwh as we use, on an annualized basis 21 kwh a day: if I could buy that at 8p/kwh when we are not generating it might be worth exploring further...
 

bctomuk

God
Apr 24, 2021
27
9
United Kingdom
I signed up for the ‘A Shade Greener’ free solar panels so I don’t own them or benefit from FIT but benefit from using electricity produced. Would I be able to purchase a powerwall or similar storage device to store energy during the day to use at night?
 

Dilly

Active Member
Feb 24, 2020
1,871
1,534
Norfolk
I signed up for the ‘A Shade Greener’ free solar panels so I don’t own them or benefit from FIT but benefit from using electricity produced. Would I be able to purchase a powerwall or similar storage device to store energy during the day to use at night?
unless your contract states otherwise, I’d assume that you can. You are after all, just benefitting from the solar power.
The rights of the owner to collect FIT and presumably deemed export, remains unchanged.
 
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Llama.

Member
Jan 25, 2021
179
88
Leeds, UK
I have a python tech 3kwh battery and have looked at adding to that, but the ROE doesn't make any sense. At. the moment on a sunny day I get 24 to 25kwh per day and to properly make use of all that I'd need to be able to store about 22kwh as we use, on an annualized basis 21 kwh a day: if I could buy that at 8p/kwh when we are not generating it might be worth exploring further...
Sorry no vehicle to grid for Tesla’s. I’d like that too. I don’t think this is upgradable through a software update either.

I have a 4.2kw solar panel set up, with 7.2 kWh of Pylontech battery. Mine are set up so they only discharge the top 80%. So really it’s much less than 7.2 kw usable power.

And I make a very similar max solar in a day to you 20-25 kWh.

I know what you mean about the ROI on batteries if this is calculated purely based on ability to store solar production , but I wanted to be able to charge the batteries off cheap off peak power at night to discharge during the day. So this accelerates the ROI as I’m able to get electricity for 1/3 of the peak rate.

Why are you saying you would need to store all 20 kwh of your daily generation to justify more batteries? Is it because you want to be able to run off grid in a power outage? My setup needs grid power to run my inverter, so no good when the power is out. But my power never goes out.

Aside from running when the power is out. At the most you only need to store enough to get through the night to when you are running directly off live solar again.
 
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Tattersky

Member
May 17, 2019
30
27
Bilston
Sorry no vehicle to grid for Tesla’s. I’d like that too. I don’t think this is upgradable through a software update either.
It is possible for EU Model 3s to do V2G from a hardware perspective, but I cannot see Tesla doing a software update that would hurt their Powerwall sales.
 

VanillaAir_UK

Former Moderator
Jun 17, 2019
7,980
5,483
Surrey, UK
It is possible for EU Model 3s to do V2G from a hardware perspective, but I cannot see Tesla doing a software update that would hurt their Powerwall sales.

Please provide a reference for this. I’d be interested to read about it.

There was a teardown from last year that subsequently got debunked for coming to the wrong conclusion that V2G was supported.

tbh, I'm glad that it doesn't appear to be an option - I just don't think that car batteries make good home batteries and vice versa, even worse when you get no benefit with v2g other than a few pennys for the grids use of your car. You have a bit more control with v2h, but I still think you are better off with a dedicated setup. Its not like the DNO are going to let you plug your car in without going through G9x etc approval and the cost of the inverter is often overlooked.
 

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