Calculating journey cost with home charging
Discussion
Hi all, any spreadsheet pros can work this out?
I did 321 miles at the weekend starting with a full battery of 57.5KWh, filled at 7p/kwh.
I supercharged twice, totalling £17.44, for 40.5kwh. For 4 miles/kwh, that's 162 miles, 12p a mile.
How do I factor in the remaining 159 miles at 2p a mile? I though about averaging 12p and 2p to make 6p, that does kind of work here as the split is almost even, but if the supercharged miles were a lot higher, averaging like that wouldn't make sense.
Any ideas?
I did 321 miles at the weekend starting with a full battery of 57.5KWh, filled at 7p/kwh.
I supercharged twice, totalling £17.44, for 40.5kwh. For 4 miles/kwh, that's 162 miles, 12p a mile.
How do I factor in the remaining 159 miles at 2p a mile? I though about averaging 12p and 2p to make 6p, that does kind of work here as the split is almost even, but if the supercharged miles were a lot higher, averaging like that wouldn't make sense.
Any ideas?
Ideally you need to know how much it cost to refill the battery (to the same level as the start of the trip) at home after the trip.
For example I did a long round trip over the weekend:
About 430 miles. Started with a 100% battery, and recharged last night to 100% as I have a reasonably long drive today.
On the trip I added 81.8 kWh via superchargers at a total cost of £35.36
According to my Ohme app last night my home charger added 63.7 kWh at a cost of £4.46
So total consumption for the trip was 145.5 kWh and cost was £40.02 for the 430 miles. So average cost per mile 9.3p and 2.95 miles per kwh. I got home with 20% battery so could have saved some money by not filling as much at the last charging stop.
During the trip the car generally displayed a better consumption rate than this, maybe 3.5 miles per kwh. The weather (and speed!) had an impact on the average consumption rate, as I can get 4 miles per kph on a steady drive in mild weather. Also I had more charge stops than needed so I guess battery preconditioning added to the consumption.
I am new to the EV game so keeping an eye on the costs at the moment. I don't think 10kwh delivered via a charger equals 10kwh added to the car, due to some inefficiencies in the charging system.
As a comparison if this trip ad been in my previous diesel SUV cost per mile would have been about double.
For example I did a long round trip over the weekend:
About 430 miles. Started with a 100% battery, and recharged last night to 100% as I have a reasonably long drive today.
On the trip I added 81.8 kWh via superchargers at a total cost of £35.36
According to my Ohme app last night my home charger added 63.7 kWh at a cost of £4.46
So total consumption for the trip was 145.5 kWh and cost was £40.02 for the 430 miles. So average cost per mile 9.3p and 2.95 miles per kwh. I got home with 20% battery so could have saved some money by not filling as much at the last charging stop.
During the trip the car generally displayed a better consumption rate than this, maybe 3.5 miles per kwh. The weather (and speed!) had an impact on the average consumption rate, as I can get 4 miles per kph on a steady drive in mild weather. Also I had more charge stops than needed so I guess battery preconditioning added to the consumption.
I am new to the EV game so keeping an eye on the costs at the moment. I don't think 10kwh delivered via a charger equals 10kwh added to the car, due to some inefficiencies in the charging system.
As a comparison if this trip ad been in my previous diesel SUV cost per mile would have been about double.
P675 said:
Hi all, any spreadsheet pros can work this out?
I did 321 miles at the weekend starting with a full battery of 57.5KWh, filled at 7p/kwh.
I supercharged twice, totalling £17.44, for 40.5kwh. For 4 miles/kwh, that's 162 miles, 12p a mile.
How do I factor in the remaining 159 miles at 2p a mile? I though about averaging 12p and 2p to make 6p, that does kind of work here as the split is almost even, but if the supercharged miles were a lot higher, averaging like that wouldn't make sense.
Any ideas?
To solve this, first sum up the total journey cost, then divide by total mileage.I did 321 miles at the weekend starting with a full battery of 57.5KWh, filled at 7p/kwh.
I supercharged twice, totalling £17.44, for 40.5kwh. For 4 miles/kwh, that's 162 miles, 12p a mile.
How do I factor in the remaining 159 miles at 2p a mile? I though about averaging 12p and 2p to make 6p, that does kind of work here as the split is almost even, but if the supercharged miles were a lot higher, averaging like that wouldn't make sense.
Any ideas?
Supercharging is £17.44, that's easy.
Home charging is 57.5 kWh x £0.07 / kWh = £4.03
Total charging cost = £21.47
Miles = 321
Cost per mile = 321 / £21.47 = 7p per mile
The above assumes that you ran the car down to 0% charge at the end of the 321 miles, which is unlikely.
If you know what % charge you had remaining, subtract that from the 57.5 kWh battery capacity. So if for example you had 25% charge left at the end, the home charging cost would be three quarters of the full tank, so £3 instead of £4, so £1 cheaper.
Except that..if you're charging from AC at home there are significant charging losses through the DC converter. I think it's around 10%.
Most people look at the the kWh sent to the car when paying at a DC charger, but only look at the kWh received by the car when AC charging and have ignored the AC/DC losses.
Most people look at the the kWh sent to the car when paying at a DC charger, but only look at the kWh received by the car when AC charging and have ignored the AC/DC losses.
Paul Drawmer said:
Except that..if you're charging from AC at home there are significant charging losses through the DC converter. I think it's around 10%.
Most people look at the the kWh sent to the car when paying at a DC charger, but only look at the kWh received by the car when AC charging and have ignored the AC/DC losses.
The losses may be 'significant' but 10% of £4 is an extra 40 pence. Which lifts the total cost of the 321 mile journey from 6.69p to 6.81p a mile.Most people look at the the kWh sent to the car when paying at a DC charger, but only look at the kWh received by the car when AC charging and have ignored the AC/DC losses.
If you truly care, measure the electricity draw and add the % losses to the electricity price (e.g. 7.7p per kWh delivered), and put that in the calculations. But I think we're getting into the trivial at this point.
The whole thing is just deranged wibble.
There is no point averaging the cost of charging home and away.
It's like worrying what the average price of coffee is when you drink 20 cups at home every week at 20p, and 5 cups out at £3.50.
No point averaging the cost, because there is no average cup of coffee which costs you 86p.
You have a base cost of home charging, then any journey which involves 'away' charging costs x-amount after the first 150 miles or whatever.
Short journeys are cheap going on free, long journeys cost similar to petrol. The End.
Generally, the big cost is owning the car, it's costing you thousands a year whether you use it or not.
There is no point averaging the cost of charging home and away.
It's like worrying what the average price of coffee is when you drink 20 cups at home every week at 20p, and 5 cups out at £3.50.
No point averaging the cost, because there is no average cup of coffee which costs you 86p.
You have a base cost of home charging, then any journey which involves 'away' charging costs x-amount after the first 150 miles or whatever.
Short journeys are cheap going on free, long journeys cost similar to petrol. The End.
Generally, the big cost is owning the car, it's costing you thousands a year whether you use it or not.
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