Confused about kWh charging costs - please help!

[Yorkshire Lad]

So, I'm considering buying a Mini Electric or something similar as a run about for me and my wife. The battery capacity is 32.6kWh with a useable capacity of 28.9kWh and a potential range of around 110 miles.

With this in mind and the fact that we haven't got a wall box charger and would be just using the standard three pin plug method, I am wondering how much it is likely to cost to charge it up.

We are with Octopus and the electricity tariff is currently 22.94p /kWh so I would be grateful if someone with a bit more knowledge about these things can enlighten me on the potential cost to charge the car at this rate. I am going to speak to Octopus as they do a lower overnight tariff between 00:30 and 05:30 so this may work better.

Any help would be greatly appreciated.

Cheers

Andrew

[V8 Stang]

Around £6.50 for a full battery. However its unlikely you will be completely flat when charging?

It will be around a 1/3 of that with an overnight tariff.

I use E-ON as they do 7 hours at cheap rate.

However with a granny charger, that will take around 14 hours to charge.

[silentbrown]

Yorkshire Lad said:

Any help would be greatly appreciated.

It's not rocket surgery: Call it 29kWh capacity, and 23p/kWh = £6.67 to fill from 'empty'.
110 mile range, so ~6p/mile.

With a 13A charger you can't charge faster than around 3KW, so 5 hours of cheap electricity will only half-fill the battery (15kWh).

Edited by silentbrown on Monday 14th July 15:26

[Discombobulate]

Allow for at least 10% loss using a granny so call it 25 - 26p/kWh for ease of calculation so £7.40 for full charge which should give you 100-120 miles range. And it will probably easily add around 10 miles an hour on a granny.
If you switch to Octopus EV tariffs (eg Intelligent) you will be charged 7p / kWh between 23:30 and 05:30 (for whole house not just charger). So £2 for a full charge - equivalent to around 250 miles per gallon for a petrol car
You will need a smart meter.

PS edited to correct poor maths

Edited by Discombobulate on Monday 14th July 18:24

[sixor8]

silentbrown said:

It's not rocket surgery: Call it 29kWh capacity, and 23p/kWh = £6.67 to fill from 'empty'.
110 mile range, so ~6p/mile.

With a 13A charger you can't charge faster than around 3KW, so 5 hours of cheap electricity will only half-fill the battery (15kWh).

Edited by silentbrown on Monday 14th July 15:26

It'll be much less than that. Most EV 3pin charger plugs limit the supply to 10A max. My Honda eNy1 charges at about 1.8 kW per hour (net). Even less in mid winter.

[Sheepshanks]

sixor8 said:

silentbrown said:

It's not rocket surgery: Call it 29kWh capacity, and 23p/kWh = £6.67 to fill from 'empty'.
110 mile range, so ~6p/mile.

With a 13A charger you can't charge faster than around 3KW, so 5 hours of cheap electricity will only half-fill the battery (15kWh).

Edited by silentbrown on Monday 14th July 15:26

It'll be much less than that. Most EV 3pin charger plugs limit the supply to 10A max. My Honda eNy1 charges at about 1.8 kW per hour (net). Even less in mid winter.

...and the lower the charge rate, the greater the charging losses are. 20% is likely, could be more.

On cheap electricity it's still buttons though.

[wyson]

At least change your socket for an EV specific one. They aren’t expensive and will handle the continuous high current and heating effects over time better.

Not sure why you aren’t getting a proper wall box though. It would drive me mad granny charging an EV.

[confused_buyer]

Just get a proper charger, consider it a long term investment. It'll be safer, simpler, you'll have access to better tariffs and you'll be able to top the car up faster if you need to.

[vladcjelli]

confused_buyer said:

Just get a proper charger, consider it a long term investment. It'll be safer, simpler, you'll have access to better tariffs and you'll be able to top the car up faster if you need to.

This.

A 7.4kw charger like the one we’ve got (it’s just been reduced by £60-70 since we bought it) makes it a breeze.

This one -

https://www.electricpoint.com/wallbox-pulsar-max-7...

Don’t know what you’ll pay for installation, I replaced an older, broken charger with this so didn’t need to get a man in as the wiring was ready and waiting. Can’t be much though can it?

[LaserTam]

Be aware of potential risks of using granny charger. Plug socket can over heat.

[Chris Type R]

LaserTam said:

Be aware of potential risks of using granny charger. Plug socket can over heat.

^ this - I believe that you can get EV rated sockets and there's further info in the 'safety precautions' section of this page - https://toughleads.co.uk/products/ev-socket

[ashenfie]

sixor8 said:

silentbrown said:

It's not rocket surgery: Call it 29kWh capacity, and 23p/kWh = £6.67 to fill from 'empty'.
110 mile range, so ~6p/mile.

With a 13A charger you can't charge faster than around 3KW, so 5 hours of cheap electricity will only half-fill the battery (15kWh).

Edited by silentbrown on Monday 14th July 15:26

It'll be much less than that. Most EV 3pin charger plugs limit the supply to 10A max. My Honda eNy1 charges at about 1.8 kW per hour (net). Even less in mid winter.

At that rate a 0-100% would take around 16hours, even a more sendable 20-80 it would be over 9 hours.

[Actual]

You don't need a EV charger installation to get an EV tariff.

For some time I only had a 3 pin plug charger adapter and still had an EV tariff.

British Gas
Electric Vehicle Off Peak
7.90p per kWh
Electric Vehicle Peak
25.98p per kWh
Standing charge
48.69p per day

I could have done the same with Octopus but I had to switch away to get off an Economy 7 tariff and have a smart meter installed (Octopus could not cope with that).

We also run the dishwasher, washing machine and dryer after midnight for cheaper electricity.

[Discombobulate]

LaserTam said:

Be aware of potential risks of using granny charger. Plug socket can over heat.

I charged mine for a year during Covid on a granny. No issues, but we have a decent dedicated, new waterproof outdoor socket.

[gord115]

LaserTam said:

Be aware of potential risks of using granny charger. Plug socket can over heat.

We have a Kia E-niro and use the granny charger all the time. I fitted one of these and it never gets hot.

https://www.halfords.com/motoring/tools/garage-equ...

[Yorkshire Lad]

Thanks for all the information, I'll see what happens once we get the car and decide what will work best for us.

[ScoobyChris]

Yorkshire Lad said:

Thanks for all the information, I'll see what happens once we get the car and decide what will work best for us.

Think this is the sensible approach. I was all set on a wall box, but in the end we re only charging once a week and the granny charger with Octopus Go works fine to get the car close enough to 100% during the off peak window. If/when I get my EV (which will have a significantly bigger battery) suspect that will be the point where we go with a wall box!

Chris

[Yorkshire Lad]

Thanks for all the information, I'll see what happens once we get the car and decide what will work best for us.