Charging cost and time

[Ankh87]

Just got my Tesla M3 LR and done a few trips to work and back.
So now I'm trying to work out the cost and how long I need to charge for.
I only have a 3 pin socket at home at the moment. From what chatgpt is telling me, I'm not entirely sure it's correct. Also I'm trying to work out the savings by changing tarrif.

So my journeys total energy used is 15.5kWh. Currently the tarrif I'm on is 0.27p all day.

The tarrif I'm looking at is 5 hours at 0.089p and then the rest of the it's 0.2937p.

If someone who's smarter then me obviously could work this out, I'd appreciate it.

Chatgpt is saying current tarrif would cost £4.03 but if I change tarrif it would be £2.19.

Would also be good to know how long it would take for a standard 7kW home charger.

[samoht]

For timing, 15.5 kWh on a three-pin charger at ~2.2 kW will take approx 7hours (15.5 / 2.2 = 7.05).
With a hardwired home charger at 7kW, it would be 15.5 / 7 = 2hrs 13 mins

For costs:
- On your current all-day tariff, 15.5 kWh x 27 p/unit = £4.18 (whatever sort of charger you use)

- On the split rate tariff with the three-pin charger you pay
5 hours x 2.2 kW x 8.9p = 98p
+2 hours x 2.2 kW x 29.37p = £1.32
for a total of £2.30

- With a 7kW home charger, all charging is at the lower rate, so
15.5 kWh x 8.9p = £1.38


If you go to the split rate, obviously you're paying a higher rate during the day. 2.37p a unit surcharge at the UK average electricity consumption of 2700 kWh is £63.99 a year, or 17.5p/day.

However you'd only have to shift about 15% of your domestic consumption into the overnight period (a dishwasher or laundry run, say) to break even on domestic usage, thus leaving the charging savings undiminished.


If I were you, I'd just sign up for Intelligent Octopus Go. I believe it natively supports Teslas, so you could do that with either the three-pin or a 7kW charger. With IOG you charge the car at 7p a unit for as long as it needs charging, without paying a surcharge in daytime. So swap electricity supplier, zero upfront cost, cheaper overnight for as long as you need, and no extra daytime cost.

Edited by samoht on Thursday 18th September 23:10

[Mammasaid]

Ankh87 said:

Just got my Tesla M3 LR and done a few trips to work and back.
So now I'm trying to work out the cost and how long I need to charge for.
I only have a 3 pin socket at home at the moment. From what chatgpt is telling me, I'm not entirely sure it's correct. Also I'm trying to work out the savings by changing tarrif.

So my journeys total energy used is 15.5kWh. Currently the tarrif I'm on is 0.27p all day.

The tarrif I'm looking at is 5 hours at 0.089p and then the rest of the it's 0.2937p.

If someone who's smarter then me obviously could work this out, I'd appreciate it.

Chatgpt is saying current tarrif would cost £4.03 but if I change tarrif it would be £2.19.

Would also be good to know how long it would take for a standard 7kW home charger.

15.5kWh @ £0.27/kWh = £4.19

15.5 kWh @ £0.089/kWh = £1.38

HTH

[Ankh87]

samoht said:

For timing, 15.5 kWh on a three-pin charger at ~2.2 kW will take approx 7hours (15.5 / 2.2 = 7.05).
With a hardwired home charger at 7kW, it would be 15.5 / 7 = 2hrs 13 mins

For costs:
- On your current all-day tariff, 15.5 kWh x 27 p/unit = £4.18 (whatever sort of charger you use)

- On the split rate tariff with the three-pin charger you pay
5 hours x 2.2 kW x 8.9p = 98p
+2 hours x 2.2 kW x 29.37p = £1.32
for a total of £2.30

- With a 7kW home charger, all charging is at the lower rate, so
15.5 kWh x 8.9p = £1.38


If you go to the split rate, obviously you're paying a higher rate during the day. 2.37p a unit surcharge at the UK average electricity consumption of 2700 kWh is £63.99 a year, or 17.5p/day.

However you'd only have to shift about 15% of your domestic consumption into the overnight period (a dishwasher or laundry run, say) to break even on domestic usage, thus leaving the charging savings undiminished.


If I were you, I'd just sign up for Intelligent Octopus Go. I believe it natively supports Teslas, so you could do that with either the three-pin or a 7kW charger. With IOG you charge the car at 7p a unit for as long as it needs charging, without paying a surcharge in daytime. So swap electricity supplier, zero upfront cost, cheaper overnight for as long as you need, and no extra daytime cost.

Edited by samoht on Thursday 18th September 23:10

Thanks. So I'm better off with a wall charger obviously and the prices from chatgpt were right.
I'm with octopus but i were looking at the other tarrif. The intelligent tarrif is cheaper so probably best going off of that. I could nearly get the car charged up in those 6 hours which would be cheap.

[Gone fishing]

Intelligent Octopus Go may also give you extra slots at the cheaper rate when needed so you might find it’s a little cheaper still. We’ve an EV with a 100kwh battery and even at 7kw it can take 15hours to fill, we got home yesterday after a long trip and near empty, plugged in and Octopus put us on the cheap rate from 4pm all the way through, and the washing machine worked all evening too on the cheap rate as a result. There’s no guarantee it will, but I’ve found it gives extra slots more often than not.

So I’d be more inclined to say switch to IOG and worry less about your charger at the moment,

[gmaz]

Ankh87 said:

Thanks. So I'm better off with a wall charger obviously and the prices from chatgpt were right.
I'm with octopus but i were looking at the other tarrif. The intelligent tarrif is cheaper so probably best going off of that. I could nearly get the car charged up in those 6 hours which would be cheap.

IOG will give you more hours if you need it, so if you are in the unusual position of needing a 0% to 100% charge it will provide 10 hours cheap rate as long as you plug it in in the evening.

[Tony1963]

And, with IOG, you sometimes receive a notification from Octopus that there’s a free hour coming up.

If I can, a put the car on a charge, the oven on self-cleaning, the dishy and washy on, tumbly on, and maybe use the microwave.

They offer that when renewable energy is going to provide too much energy for the predicted demand.

[Ankh87]

Thanks all.

Going to arrange IOG then. I'm with Octopus now but I don't have a smart meter. So I will have to wait for that to be installed before fully switched. My plan is to get a home wall box at some point, assuming the prices will drop maybe a year or so.

[ShortBeardy]

Isn't the fuse for a 240V AC 3 pin domestic plug 13A.
240 x 13 is 3.1kW not 2.2
?

Other options include a higher current rating 240V supply such as you might see for a cooker or dryer. If your panel is close to the desired charging point, then having a high current charging outlet installed might be beneficial on the basis of shorter charging times (and perhaps a bit more freedom to choose electrical supply plans). You can use the Tesla mobile charger and the `Blue adapter' which offers 32A rating.


As an aside I charge at home (US) and use the cheap Tesla mobile charger but we had a 2 phase outlet (240V) put in the garage so it will charge at 32A 240V. This more than enough for us as charging speed is not ultimate requirement when you have all night.

[Gone fishing]

ShortBeardy said:

Isn't the fuse for a 240V AC 3 pin domestic plug 13A.
240 x 13 is 3.1kW not 2.2?

No. 13amp is ok for short durations but a continuous load like charging the limit is 10amps.

[plfrench]

Consider Ovo Anytime too.

I’m paying 7p/kWh for EV 21.8p/kWh for house. No limited window. Check your regional household price though as that does seem to vary depending on where you are in the country.

Also works well with multiple vehicles simultaneously should that be useful.

[sixor8]

Tony1963 said:

And, with IOG, you sometimes receive a notification from Octopus that there s a free hour coming up.

If I can, a put the car on a charge, the oven on self-cleaning, the dishy and washy on, tumbly on, and maybe use the microwave.

They offer that when renewable energy is going to provide too much energy for the predicted demand.

They offer that on any tariff, I believe. I used to get it regularly on just Octopus Go. I still get notified of them by email a few hours before, even though I switched to EON Next Drive in May.

[Tony1963]

sixor8 said:

They offer that on any tariff, I believe. I used to get it regularly on just Octopus Go. I still get notified of them by email a few hours before, even though I switched to EON Next Drive in May.

But charging a car battery at 7.5kw is quite a chunk of energy compared to the usual domestic usage.

[blueacid]

Tony1963 said:

But charging a car battery at 7.5kw is quite a chunk of energy compared to the usual domestic usage.

Indeed - in my case the car represents just over half of all my electricity use; and I was a high user to begin with (no gas: electric cooker, electric heating, immersion heater for hot water).