Monthly Cost Calculation

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Discussion

uuf361

Original Poster:

3,155 posts

227 months

Thursday 20th April 2023
quotequote all
I'm about to get my first EV and trying to calculate my monthly fuel cost but it seems to low!

Is it as simple as follows:

I do roughly 1,000 miles per month and the car will get roughly 200 miles per charge from a 60kwh battery, thus it would need charging 5 times from empty to full (I appreciate it'll always be topping up), and therefore I would use 300kwh of charge at my night time rate of 9.3p/kwh

My simple calculation equates to only £27.90 (+VAT) per month which seems rather low.

Am I doing it right? confused

TheRainMaker

6,523 posts

247 months

Thursday 20th April 2023
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Yep, just add on 15-30% for charging losses and you are there.

Sheepshanks

34,201 posts

124 months

Thursday 20th April 2023
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Your range (as in, miles per kWh) figures may be a little optimistic, especially in winter. What kind of journeys are you doing? Bear in mind economy in an EV is the opposite of an ICE - so they can be better around town than on long trips.

If you didn't realise already, if you're charging at home the VAT is only 5%.

uuf361

Original Poster:

3,155 posts

227 months

Thursday 20th April 2023
quotequote all
Range for the car is 280 miles, and all the reviews online say c.200 is achievable even through the winter.

My journeys are mostly local (a/B roads) of 10 miles each way) plus a 120 mile round trip to work once each week on the M25/M4 where 70mph would be aspirational and it's more like 50-60mph.

I had forgotten about only 5% VAT, and the cost just seems exceptionally low, but that's good, especially as I should also be able to charge at work for free too, if I get up early enough!

poo at Paul's

14,311 posts

180 months

Thursday 20th April 2023
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At that price per unit, should be about 6p per mile in practice, I reckon.

Mr E

22,032 posts

264 months

Thursday 20th April 2023
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You may also burn a bit of power while cabin/battery preconditioning.

But yes, typical EV is 250-400Wh per mile (so 4-2.5 miles per KWh). At an overnight low cost charge rate, pennies per mile.

manracer

1,546 posts

102 months

Thursday 20th April 2023
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We cover around 800 miles a month (80% local, 20% motorway) and over the last 4 months the average cost per month is £35.

We use intelligent octopus for overnight charging.

This is for a model 3 performance that always has the heating on 28 degrees when O/H drives and when I drive, I dont think about economy i.e. drive quickly and usually at night. O/H covers around 85% of the driving

Sheepshanks

34,201 posts

124 months

Thursday 20th April 2023
quotequote all
poo at Paul's said:
At that price per unit, should be about 6p per mile in practice, I reckon.
confused - it should be way less than that?

TheDrownedApe

1,151 posts

61 months

Thursday 20th April 2023
quotequote all
Sheepshanks said:
confused - it should be way less than that?
yeah ours averages 28.5Kwh/100 miles which is about 2p a mile on our 7p kwh leccy rate

Sheepshanks

34,201 posts

124 months

Thursday 20th April 2023
quotequote all
You may also need to do that other thing some people have got their knickers in a twist about and see how much your 'daytime' electricity bill is going to increase on the the EV tariff (if the day rate is higher than standard).

uuf361

Original Poster:

3,155 posts

227 months

Thursday 20th April 2023
quotequote all
I'm on a (great) fixed rate until the end of next summer with economy 7 so won't be changing anything until then and only charging overnight when it's cheap.

SWoll

19,074 posts

263 months

Thursday 20th April 2023
quotequote all
TheRainMaker said:
Yep, just add on 15-30% for charging losses and you are there.
What EV loses 30% during charging on a 3 pin or 7kWh charger?

10% is about right from what I've experienced across 3 different EV's and 50k miles of home charging, so based on the OP's numbers I'd suggest 3 miles/kWh, or 3.1ppm at 9.3p kW. So £31 for 1000 miles including losses would seem about right.

Edited by SWoll on Thursday 20th April 12:10

Penny Whistle

5,783 posts

175 months

Thursday 20th April 2023
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For the purposes of your calculation, the car's range is irrelevant. All you need to know is how many miles you can do per kWh (over the last 11 months mine has averaged 3.28 mls/kWh), which will tell you how many kWh you need per month. Then multiply that by however much you pay per kWh. So : 1000/3.28 = 305kWh which at 9.3p/kWh will cost £28.35. As you are buying all that (rather than getting any from PV for example), then you need to add on say 10% for efficiency losses and 5% for VAT. I'd budget £35/month.

manracer

1,546 posts

102 months

Thursday 20th April 2023
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I also find that even though I should get 6hrs off peak electricity that I usually get 7 or 8 hrs if that is how long the car will take to reach the specified charge limit.

Regarding the increase to the daytime rate, I just switched my dishwasher, washer and dryer to kick off at 11.30pm and this alone has reduced my overall daily spend.

Equally, moving the gas to octopus tracker has reduced my gas spend significantly. I was on 10p/kWh and now its usually around 6p, today is 4.88p!

TheRainMaker

6,523 posts

247 months

Thursday 20th April 2023
quotequote all
SWoll said:
TheRainMaker said:
Yep, just add on 15-30% for charging losses and you are there.
What EV loses 30% during charging on a 3 pin or 7kWh charger?

10% is about right from what I've experienced across 3 different EV's and 50k miles of home charging, so based on the OP's numbers I'd suggest 3 miles/kWh, or 3.1ppm at 9.3p kW. So £31 for 1000 miles including losses would seem about right.

Edited by SWoll on Thursday 20th April 12:10
Reading up on it,

https://www.energate-messenger.com/news/225482/ada...



SWoll

19,074 posts

263 months

Thursday 20th April 2023
quotequote all
TheRainMaker said:
smile

According to a completely unbiased test funded by the German automobile association..

Remember reading it at the time, and the big losses were all seen on a single model (Zoe) in winter. Here are the results for the rest of the cars tested.



Using a dedicated wallbox charger would appear to make my 10% estimation a little high, and even on a 3 pin every other model is at 15% or lower.

TheRainMaker

6,523 posts

247 months

Thursday 20th April 2023
quotequote all
SWoll said:
smile

According to a completely unbiased test funded by the German automobile association..
Don't shoot the messenger hehe

SWoll

19,074 posts

263 months

Thursday 20th April 2023
quotequote all
TheRainMaker said:
SWoll said:
smile

According to a completely unbiased test funded by the German automobile association..
Don't shoot the messenger hehe
Fair enough. smile

They've always had it in for the French, as well all know. wink

UrbanAchiever

188 posts

141 months

Saturday 22nd April 2023
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If you choose OVO energy and use their charge anytime tariff, you won't pay any more than 34p/kwh for non-EV use. And the EV charging cost is 10p/kwh.

Costs us £6.90 to charge from zero to 100%. And that is good for 200 - 240 miles depending on weather/conditions/driving style.

So between 3.45p and 2.86p per mile.

uuf361

Original Poster:

3,155 posts

227 months

Monday 24th April 2023
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Until my fixed rate ends I won't be changing as my daytime rate is under 25p and the night time is just over 9p.