Calculating Energy use over a Year

[Staypuffman]

With all the energy price increases, i wanted to work out how much energy, on average, it would take to charge my Model 3 (when it arrives) over the year.

And i know the mileage you get on a full battery would vary due to different factors, but after a standard achievable mileage.

Battery size is 50kWh for a standard Model 3(?) . And my mileage would be 8000 for a year.

 

[PITA]

Say 300 Wh/m (which is high consumption)

3 miles per 1 kWh

8000 miles = 2,666 kWh

2,666 kWh @ 5p per 1 kWh = £133 for 8000 miles

2,666 kWh @ 30p per 1 kWh = £800 for 8000 miles

 

[MrBadger]

Simple answer - Completely different to what you plan on. Its a rabbit hole. How often will you use sentry, what's your long/sort trip split like, how warm do you like the cabin, what fan speed are you going to use, how much charge losses are you going to experience etc etc. Not everything comes into how far or how efficiently the car is going to be driven.

Loads of threads elsewhere explaining why expectations and reality differ for so many. Here is one for starters - Stated Range vs Real World

 

[PITA]

Say 250 Wh/m

4 miles per 1 kWh

8000 miles = 2,000 kWh

2,000 kWh @ 5p per 1 kWh = £100 for 8000 miles

2,000 kWh @ 30p per 1 kWh = £600 for 8000 miles

This is why Home Charging at cheap rate tariffs are important & cost effective

 

[26ct2143]

Say 300 Wh/m (which is high consumption)

3 miles per 1 kWh

8000 miles = 2,666 kWh

2,666 kWh @ 5p per 1 kWh = £133 for 8000 miles

2,666 kWh @ 30p per 1 kWh = £800 for 8000 miles

Agreed, if you go with 3 miles per 1 kwh you will probably be looking at it fairly pessimistically.
You should normally manage better than this. But winter use etc, it'll be about this.

 

[tonyj01]

You can use an app like TeslaFi to connect to the car and give you long term usage figures retrospectively.

Also if cost is a concern, (nobody likes to pay more!) get Economy 7 installed or a tariff like Octopus Go. The latter has a four hour night rate of 5p per kWh.

Overall, in my home, over the last six years, we have run two EVs, averaging about 16,000 miles pa, cost has been about £40 a month extra on the bill using night time charging.

So your 8000 miles pa might cost £20 a month with home connection.

Tony

 

[GeorgeSymonds]

Its also further confused by how much you use sentry mode (that uses not an inconsiderable amount of energy over a year) and charging inefficiencies and of course the mix of charger types as the price per kwh can vary quite a lot. Unless I'm mistaken the 5p per kwh is simply not available now unless you already have it, and those that have it I believe its going up when any fixed period ends. If I'm right I wish people would stop quoting the unobtainable as it doesn't help anyone going forward.

While an EV is cheaper in general that a petrol or diesel car to run unless you live of expensive rapid chargers, the cost isn't negligible unless you have access to free electricity somehow.

As a rough, cautious guide, home charging, not a particularily special tariff of 22p/kwh, allowing for 25% charging inefficiency and low use of sentry mode so little vampire drain, a back of an envelipe estimate might be:

8000 x 0.275 (kwh per mile) x 1.25 (charging inefficiency) x 22p (price per kwh) = £600 or about 7 to 8p a mile. Thats about half the price of an efficient ICE.

 

[PITA]

Its also further confused by how much you use sentry mode (that uses not an inconsiderable amount of energy over a year) and charging inefficiencies and of course the mix of charger types as the price per kwh can vary quite a lot. Unless I'm mistaken the 5p per kwh is simply not available now unless you already have it, and those that have it I believe its going up when any fixed period ends. If I'm right I wish people would stop quoting the unobtainable as it doesn't help anyone going forward.

While an EV is cheaper in general that a petrol or diesel car to run unless you live of expensive rapid chargers, the cost isn't negligible unless you have access to free electricity somehow.

As a rough, cautious guide, home charging, not a particularily special tariff of 22p/kwh, allowing for 25% charging inefficiency and low use of sentry mode so little vampire drain, a back of an envelipe estimate might be:

8000 x 0.275 (kwh per mile) x 1.25 (charging inefficiency) x 22p (price per kwh) = £600 or about 7 to 8p a mile. Thats about half the price of an efficient ICE.

What do you mean "quoting the unobtainable"

EDF are quoting 4.5p right now on their GoElectric Tariff... so it could be even cheaper....

Or charging from Solar Panels in 2 months time, in which case it'll be FREE...

 

[GeorgeSymonds]

What do you mean "quoting the unobtainable"

EDF are quoting 4.5p right now on their GoElectric Tariff... so it could be even cheaper....

Or charging from Solar Panels in 2 months time, in which case it'll be FREE...

And "...from 36p at all other times" - hardly a bargain for the rest of the day undoing any saving you might make at night

 

[PITA]

And "...from 36p at all other times" - hardly a bargain for the rest of the day undoing any saving you might make at night

... not in our use case, but carry on

 

[qwickshot]

The cost to charge your car really depends on your other energy usage and what tariff you currently get and what’s available.

If you still have a ‘good’ fixed tariff like me at around 20p/kWh and do relatively low mileage, you’ll probably find that staying in the flat rate is better for your overall energy cost. Likewise you may save money by going onto a time of use tariff.

Only really you can work this out yourself based on your current bills and energy use pattern. I’d suggest that 90% of your household use will be on the day rate but ‘it depends’. A smart meter should help you work that out. Check it before you go to bed and then when you wake up, that will tell you your house standing draw and then prorate that for 4 hours. Also consider that you can run appliances overnight so try that and check the energy use there as well.

An SR+ will average about 260wh/mile, but then you need to add back charging losses and energy used to pre-heat/defrost the car. You’ve got two options here go with a conservative flat rate of 333wh/mile or try and add back charging losses and pre-heat/defrost use.

I would use the flat rate for now, I think Octopus suggests that around 85% of charging is done on the day rate, so id use the flat rate multiply it by your mileage and apportion it to 85% night and 15% day. Then add in hour come energy use and see how it compares to your current tariff.

Your home charger (like a hypervolt) when you get it may have some detailed analytics you can draw from but you’ll need time to gather data. There are the 3rd party Tesla Apps also but they don’t take into account charging losses so you’ll need to add that back, again you’ll need time to gather data.

You also need to take account for public charging, id suggest 15% of your miles from public chargers. I’d account for at least 40p/kWh from them but some can be free. These of course will need to be deducted from your cars energy use when considering which home tariff is best for you. Only really you can tell how much public charging you expect to do.

In short, I’d take the above, plot it into a spreadsheet and see what the answer is.

For me in my circumstances, there was no benefit from moving to a time of use tariff like Octopus Go over my flat 20p/kWh price which is locked into sept 2023.

The term ‘your mileage may vary’ is particularly key here.