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How much, roughly, might one be looking at for installing some solar panels on a garage roof to charge an EV?
 

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Many variables....

Assuming you have a 3 pin charger (granny lead) that would need 2.5kWh. A garage roof may well not be big enough to mount enough panels. A 150W panel is over a meter tall and at least 500mm wide. You would need 8 as a minimum, but preferably 12 plus so it also works without direct sunlight.

People typically pay many thousands to install that size array. Actual hardware, plus inverter comes in at few thousand.
 

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Unfortunately it is "how long is a bit of string"
If the car is not available to charge when the sun is around then zilch but if a 2nd car for the school run etc plugged in most of the day then poss. Then how many miles are you doing and .......

In pure economic terms this is probably a non starter as with Smart meters and time of use tariffs it makes more sense to charge at night.

However economics to one side slightly it can work and help run the house, heat hot water and other things particularly for people working at home. Return on investment could be of the order of 6-7% and the capital cost of the order of £5K-5.5K. Do need something close to a south facing roof.

I have solar panels and i get a inner satisfaction knowing i am helping the planet.
 

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I've got a 4kW setup on my roof; 4kW is the most it ever produces, on a a perfect summers day around noon and the daily total might reach 30 kWh. No probs charging at 10A for quite a few hours. 3.3kW charging is sometimes possible, but there's the house drawing a bit, and I prefer to not import, plus my car only takes max 12 kWh at a max 14A rate for a full charge anyway, so I use 10A a lot in summer.

Right now a perfect day might produce 6kWh, and the max is about 1.2 kW, so even charging at the lowest 6A as per today (sunny) I'm importing from the grid. But it's nice to offset the grid imports!

Over a year, my panels produce 4000 kWh, and coincidentally that's what my house (without the car, and without panels) is using up. With the panels in, my house bill has dropped to 3000 kWh, so the panels have contributed 1000 kWh to that. My car also takes 1500 kWh for 6000 miles leccy driving, so in total my panels at the moment are giving me 2500 kWh, and exporting 1500 kWh back to the grid. If I change to a full Bev then I'd be doing 12k miles p.a. which would use up that exported 1500 kWh nicely!

House is a 4-bed det, attached gge, 70's brick box of zero architectural merit. 2.5 adults resident for the figures I gave. Hopefully this might give you some idea of what your usage & savings could be.
There's another useful saving around £150 p.a., as I have a Solic 200 diverter which feeds excess leccy to the immersion tank. So ancient inefficient gas boiler is now off from April to Sept, reducing that bill & CO2 a bit.

Some people deliberately "over-panel", where they put maybe 20 panels rated 250W each on their roof, but these feed into an inverter rated 4 kW. The panels might be trying to output 5 kW on that perfect day, but the limit on the inverter clips that. The effect is they get a more reliable 4 kW for more hours in the day, but at a noticeable increase in capital cost. My system peaks at 4 kW with nothing in hand, so when a cloud comes over, you see the dip immediately.

I have Solaredge microinverters, one per panel, so a single panel shaded by the chimney doesn't affect the rest. Also if one panel or inverter dies, it's trivially easy to work out which one died! But this is probably a bit more expensive than the single-inverter systems. I used http://goinggreenrenewables.co.uk/ who did me a very good system, competently done, and working fine for the last 4 years. Very happy with them.
 

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I've got a 4kW setup on my roof; 4kW is the most it ever produces, on a a perfect summers day around noon and the daily total might reach 30 kWh. No probs charging at 10A for quite a few hours. 3.3kW charging is sometimes possible, but there's the house drawing a bit,..
Get as much solar as you can, then use a time-of-day tariff, drive the car when it is sunny (that is what it is for, isn't it?) and charge it overnight.

I bought a 6 amp EVSE lead to help charge on solar, as it only takes 1.4kW and my 4kWp panels can supply that easily....

Except, they can't in winter (they are producing 400w currently) and they can't on a typical summer's day - which is half cloud and half sun, so you would need an intelligent charger.

Solar PV goes really will with economy 7 - you get the cheap units overnight, when you want to charge, and the PV offsets the higher cost units for most of the day, even in winter. Then move your dishwasher and washing machine usage to overnight with a timer. I now use (import) much more electric overnight in the 7 hours than I do over the rest of the day: 2781 versus 1997 kWh p.a.
 

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Agreed about the cheap rate overnight, but you have to do the sums for yourself! As I'm retired, my car's on the drive often enough to be charged usefully off the panels in summer. Eco 7 wouldn't work for me as I don't do enough overnight charging/washing to offset the greater charge on daytime units. Horses for courses.
 

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With Eco 7 already installed I just charge overnight and let any solar panel surplus be exported to the grid. The price difference between my overnight E7 rate and the export rate for the (presumed) exported kWh is so small as to not be worth worrying about (I might be interested in V2G). For those without E7, the Zappi chargers can be configured to use as much surplus solar output as possible for charging.
 

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Agreed about the cheap rate overnight, but you have to do the sums for yourself! As I'm retired, my car's on the drive often enough to be charged usefully off the panels in summer. Eco 7 wouldn't work for me...
I'm very surprised. Ecotricity were my electric suppliers at the time I switched and they were good enough to give me the consumption spreadsheet from the smart meter. At 5K miles per year in the EV it was just about break-even for me, and I'm expecting to do 10K this year, so I'll be quids in.
 

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I have a 4Kw system on my house and a diverter to the immersion heater for the excess, only then does it export to the grid, so mostly free hot water (saves spending on gas). So today 11th Nov I have 7.6Kwh produced and exported .2Kwh to the grid. Not much left over for the car.
 

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I have a 4Kw system on my house and a diverter to the immersion heater for the excess, only then does it export to the grid, so mostly free hot water (saves spending on gas). So today 11th Nov I have 7.6Kwh produced and exported .2Kwh to the grid. Not much left over for the car.
Would you do better by firstly diverting the solar excess to the car, even if this means you have to spend a bit more on gas for the hot water?
 

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Hi Dave,
I've had the solar panels for 4 years and the Tesla for 4 days.
No, I get paid over 5p per Kwh for half of all I produce whether I export it or use it, and being as gas (for the hot water) costs a good deal more than 5p it makes sense to export.
Now with Octopus Go (link below) I get 4 hours per night cheap electricity at 5p per Kwh which should be enough for pretty much all my mileage.
So I have almost free hot water at night when I need it, I have very cheap electricity at night for the car when I'm not using it )12:30 - 04:40 am.
I can't see that I could get any more efficient.
 

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Hi Dave,
I've had the solar panels for 4 years and the Tesla for 4 days.
No, I get paid over 5p per Kwh for half of all I produce whether I export it or use it, and being as gas (for the hot water) costs a good deal more than 5p it makes sense to export.
Now with Octopus Go (link below) I get 4 hours per night cheap electricity at 5p per Kwh which should be enough for pretty much all my mileage.
So I have almost free hot water at night when I need it, I have very cheap electricity at night for the car when I'm not using it )12:30 - 04:40 am.
I can't see that I could get any more efficient.
I'm very similar to above, 6.72kw solar array, Octopus Agile Tariff and an I3s to charge. Have started intelligent charging no idea how the car manages it but it decides when electricity is cheapest before departure time and charges utilising solar and overnight low cost electricity. As has been said previously not much solar electricity to be had at the moment!
 

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Some people deliberately "over-panel", where they put maybe 20 panels rated 250W each on their roof, but these feed into an inverter rated 4 kW.
The 4kW rating is the largest system you can connect to the grid without prior authorisation from the DNO, if you want a bigger system then the process is you have to apply first and then get a permit. I understand it's rare for them to refuse, but they might and they might give you a value that's larger than 4k but smaller than you want installed.
 

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The 4kW rating is the largest system you can connect to the grid without prior authorisation from the DNO, if you want a bigger system then the process is you have to apply first and then get a permit. I understand it's rare for them to refuse, but they might and they might give you a value that's larger than 4k but smaller than you want installed.
The limit is actually 16A or somewhere between 3.6 & 3.8A according to local grid voltage. But that limit applies to your export so you could as HandyAndy suggested fit a lower rated inverter or even have some sort of diverter arrangement.
 

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The limit is actually 16A or somewhere between 3.6 & 3.8A according to local grid voltage.
I believe the limit is 16A per phase, so if you have a 3-phase supply you can export up to 16A on each of the three phases. I suspect for more than this the DNO would want to be sure that you cannot push the incoming P-N supply voltage above a maximum of 253 (or 254) volts, remembering that on rural distribution networks this is the low load output voltage of the 11kv - 240v transformers.
 

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How much, roughly, might one be looking at for installing some solar panels on a garage roof to charge an EV?
We install a lot of solar, plus batteries, and generally, unless it's a very large garage, it's not likely to be very cost effective. There are unavoidable fixed costs with the electrician, inverter, etc. so that you really want to maximise the number of panels installed to get your money's worth. A standard panel is 1.7m x 1m so you can probably work out how many will fit your garage - you really need to fit at least 12 (3 x 4) to be worthwhile which is why most people put them on the house roof - typical cost £4-5k. Of course, you can do the house and garage roof at the same time to save money - they'll usually all be connected to your main consumer unit. If you're out most of the day then you need to add a battery (starting at about £3k).

As suggested most UK installs have a 3.68 kW inverter as that avoids the DNO paperwork, though you can have as much as twice that in panels (e.g. 7 kWp). Myself I've gone for 10 kWp, got the DNO permission, and installed a 5kW inverter with full UPS functionality.


 

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I'm very similar to above, 6.72kw solar array, Octopus Agile Tariff and an I3s to charge. Have started intelligent charging no idea how the car manages it but it decides when electricity is cheapest before departure time and charges utilising solar and overnight low cost electricity. As has been said previously not much solar electricity to be had at the moment!
Hi Dave, I am just in the process of switching to the Octopus Go tariff , it should go live 25 Nov. I also have a 4Kw solar panel system but have the addition of a 6Kw Samsung battery installed in the loft . With this setup I never export energy back to the grid (unless the house is unoccupied whilst we are on holiday). The main rationale for choosing this Octopus tariff is to have the flexibility in the Autumn/Winter months to charge the Ampera during the 5p rate 00:30-4:30. Having read a previous thread during the winter months I will also start to programme the immersion heater to also come on during this time. I have during the summer months enjoyed cost free motoring utilising solar and the Samsung battery :)
 
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