[Mark Brownlee]

Hi all

Fuel Cost Calculator

I am currently in the market for an EV and have created a simple excel based calculator to compare fuel prices between different cars and fuel types. From speaking to colleagues and friends I think there is a wide misunderstanding of the actual cost per mile and associated cost of ownership of a BEV so I created this tool to better understand it and justify the investment for myself. With new more affordable cars coming out soon with a more usable 200+mile range such as the Jaguar I-Pace, Hyundai Kona, Leaf 60kWh and eventually the Tesla M3. The low running costs are the most attractive factor in choosing an EV as my next car and I believe these next batch will be a game changer for the market as switched on people will want to make a monthly saving. Beyond the environmental benefits which we all know, cost benefits are what drives the market.

Costs such as monthly finance, insurance etc are easy to track as you can look up bank financing or talk to dealers for a specific hire purchase costs etc. But the cost per mile driven and fuel costs are often calculated using the ((battery capacity x charge cost) / (battery range)).
I believe this is an incorrect method of calculating the driving cost as there are several variables surrounding batteries actual usable capacity and the claimed ranges at different temperatures.

Most cars seem to provide information on energy consumption such as (miles/kWh) or (kWh/100km). Using these values I have created a tool to provide per mile, monthly and yearly costs. You can add these to your usual personal monthly costs for financing, insurance, servicing, tyres etc.

For most here this will be old information that you have been taking advantage of for many years. But some people may not realise the savings they could be making or could use this to illustrate it to colleagues. From my personal figures of 22000 miles per year, I think I could be saving £230/month in fuel if I moved to an EV from my current petrol mid-life crisis.

Even comparing overall costs of ownership to a second hand efficient diesel honda civic with zero road tax, the new BEV may be still coming out cheaper in whole life cost if your a mid - high mileage driver. Maybe some of you experience hands here can pick holes in my calculations and recommend changes to the calculator. I know if doesn't account for public rapid chargers and variable electric rates, but i see most usage of these new high range BEV's being charged only 2 or 3 times per week, likely on economy 7 power plans.

I have seen a few similar posts on here with similar excel based calculators which are all excellent at their target function, but either used the battery charge cost/max range method for calculation example, or were primarily aimed at calculating the difference between battery rental and ownership example2.

Let me know your thoughts and have a play about with the sheet. I think I possibly need a fact check as i have been sucked in by the savings possible. Are real life figures which you have experienced mirrored in the calculations?

 

[GavJ]

Couple of points. Biggest one being Wh/mile. 256 seem very optimistic. While it may be achievable slipstreaming a lorry on a motorway in summer as a yearly figure is seems somewhat low. I use 333Wh per mile as a more real world figure. Also if you are doing 22,000 miles a year you don't want to be sat doing 52mph being lorries.

Also while you may charge only using economy 7 there will be times when you don't. Also you have to take into account by having economy 7 you will pay more for your daytime electric and a higher daily charge.

So based on my tariff and 333wh/mile the real world cost would be £855 for 22k. The same (@10p per mile) for ''gas' would be £2200. So a saving of £1345. But as I only do about half that it would be £673.

The other one is how long will the battery last (covering 22k per year) 4 years? Where the ''gas' one you would expect at least 6.

Anyway for me I can't charge at home so the numbers will be so far out (plus wasted time at chargers) that I'm unlikely to ever get an electric car.
I'll form an orderly queue at the 'gas' dealership in 2039 to collect my '89' plate car.

 

[cah197]

There are Teslas out there with 300,000 miles on the clock and minimal battery degradation. I’d expect most EVs to last twice as long as an equivalent ICE. Maybe three times in terms of miles driven.

In a small EV such as a Zoe/Leaf/Ioniq you’d expect 250-300 Wh/m. 330 is Tesla territory. Depends how you drive of course.

 

[GavJ]

Wow 300k! People are keeping that quiet. The only car I know if that has done that kind of mileage is Bjørn's model S. But 300k doesn't really count when you have your first battery pack replaced at 53.5k (86k km).

I'm sure my petrol car will last much longer if I replace the engine every few years.

There just doesn't seem to be enough examples about to find out how long batteries last. On autotrader there are 4 cars with over 70k on the clock. Three i3 (rex) and an 11 plate leaf.

As for usage. I'd want to drive it exactly the same way as a 'gas' car. So 70-77mph on the motorway which I'm guessing with him doing 22k per year he spends much of his time. In summer it will be less but in winter on the motorway at 70mph with the heater on (not sat in a big coat and hat with gloves). Obviously year one will be better than later years.

I'd love a Zoe or something to get some real world figures. I suspect on a summer's day when I'm not in a rush and in the mood I would be presently surprised. On a cold wet morning when I'm late for work much less so.

 

[dkelly84]

Wow 300k! People are keeping that quiet. The only car I know if that has done that kind of mileage is Bjørn's model S. But 300k doesn't really count when you have your first battery pack replaced at 53.5k (86k km).

I'm sure my petrol car will last much longer if I replace the engine every few years.

There just doesn't seem to be enough examples about to find out how long batteries last. On autotrader there are 4 cars with over 70k on the clock. Three i3 (rex) and an 11 plate leaf.

As for usage. I'd want to drive it exactly the same way as a 'gas' car. So 70-77mph on the motorway which I'm guessing with him doing 22k per year he spends much of his time. In summer it will be less but in winter on the motorway at 70mph with the heater on (not sat in a big coat and hat with gloves). Obviously year one will be better than later years.

I'd love a Zoe or something to get some real world figures. I suspect on a summer's day when I'm not in a rush and in the mood I would be presently surprised. On a cold wet morning when I'm late for work much less so.

I don't know where in the country you are, but if you want to try one, there's always here:
Home - EV Experience Centre

 

[Aragorn]

I drive my EV like i drive my ICE, as above ~"77" or a GPS 70mph on the motorway, lots of full throttle accelleration etc, and i almost never see 3mi/kwh. The long term average showing on the dash is 2.3, though that needs to be multiplied by 1.2 to give a figure thats comparative with other EV's because Merc is stupid.

So 2.76 over 16k, with a lot of 70mph motorway driving.

It does climb if you drive slower ofcourse.

Its one aspect of EV's thats very different to ICE cars and that non-EV owners might not expect. The efficiency curve of an ICE means you dont take a massive hit doing 70, and often an ICE will be more economical at 70 than it will around town. Whereas an EV will tend to be significantly worse at 70 than in town.

 

[Aragorn]

Anyway for me I can't charge at home so the numbers will be so far out (plus wasted time at chargers) that I'm unlikely to ever get an electric car.
I'll form an orderly queue at the 'gas' dealership in 2039 to collect my '89' plate car.

You could just move house at some point in the next 20 years to a house with the correct facilities...

 

[cah197]

Wow 300k! People are keeping that quiet. The only car I know if that has done that kind of mileage is Bjørn's model S. But 300k doesn't really count when you have your first battery pack replaced at 53.5k (86k km).

There's a few taxis that have done this on the same battery pack:

A Tesla Model S hits 300,000 miles in just 2 years – saving an estimated $60,000 on fuel and maintenance

Finnish Tesla Model S taxi driver crosses 400,000 km, 93% of battery life remains

Of course most normal users won't be above 100,000 miles in four years.

 

[GavJ]

I don't know where in the country you are, but if you want to try one, there's always here:
Home - EV Experience Centre

Yes it's a couple of hours away. I have driven a leaf before but only for 30 mins or so. I really want an electric car to work for me just at the moment it just all doesn't add up. Maybe if petrol prices go through the roof it might be better. But as a percentage my electric has gone up more than petrol.

 

[TomH]

One economic factor you can't exactly evaluate is the 'free' electricity you can get from solar panels.

It won't help you high mileage guys since you have to charge at night unless you get into battery storage as well. See the threads about charging.

For us oldies it can be a key factor. Zero pence per mile costs in the summer except during expeditions.

 

[Mark Brownlee]

One economic factor you can't exactly evaluate is the 'free' electricity you can get from solar panels.

Yes well that would be a separate calculation you could work out if it suited you. it wouldn't be for everyone as it would be a significant investment upfront.

Couple of points. Biggest one being Wh/mile. 256 seem very optimistic.

I think 3 miles/kWh or 16kWh/100km seems to be a reasonable enough figure to estimate average efficiency however this is the key figure which energy costs are based. Maybe this figure is too optimistic however I have based it on the various articles and reports I have read for some of the non tesla EV's.

My point for this is for you guys to question my logic because right now I think the savings are quite good compared to a new petrol/diesel car.

edit* i found an old link i used to base some the efficiency figures on, Hyundai Ioniq owners forum where they have a list of several owners driving figures. Hyundai Ioniq Owners forum