Forums

How To: Calculate Miles per Watt / KiloWatt

How To: Calculate Miles per Watt / KiloWatt

Hello all,

I just recently became a Tesla owner (delivery was 6/6/18) I would like to know how I can calculate some formulas so I can understand my range and cost better for my Model 3. With this said I don't have a kilowatt or watt meter on my home charger so I don't know how much electricity I use to charge. I'm not sure if that makes things more complicated or not. I have been recording my Trip stats before I put it on the charger. I record the following: Starting %, Ending %, miles, kilowatts, and wh/mile.

How can I calculate my miles per watt? (or is miles per kilowatt?)
What is the average miles per watt/kilowatt for a Model 3?
How can I calculate my cost per charge? I certainly know how much PSEG is charging me but as stated above I don't know how much a charge utilities. Again, I only have the Trip stats.

Thanks for all the help,
Ethan!

PS - Alternatively, if there is an online resource detailing what I'm asking for - please link me!

jamey.winchester | 7 augustus 2018

The car gives you Wh/mile - so 1000 divided by the Wh/mile gives you miles per kWh. For example, if you have 250 Wh/mile then you're at 4 miles per kWh. Your tripometer also gives you miles and kWh's, so if you reset it before your trip you can divide the 2. The Wh/mile method is more accurate as the tripometer doesn't do partial kWh's. It should be around 4 miles per kWh. If you drive like me, you get less. Some people are able to get closer to 5.

drchat | 7 augustus 2018
jamey.winchester | 7 augustus 2018

As far as how much it's costing you, miles driven divided by hr/kWh x your utility's rate per kWh is the quick and easy way. It won't account for any transmission lost, which has previously been debated as to how significant that is.

httran26 | 7 augustus 2018

I'm not sure if we know the exact size of the battery and what Tesla programs in to be the usable range. From what I read the battery is 80.5kWh with roughly 75kWh usable. So the battery % reading won't be very accurate.

So for the information you gathered, the most relevant is miles and kilowatts. The wh/mile is the average for your trip which you can also derive from your miles and kilowatts reading by doing (kilowatts * 1000) / miles.

How can I calculate my miles per watt? (or is miles per kilowatt?)
Use your reading that you have. miles / kilowatt

What is the average miles per watt/kilowatt for a Model 3?
I think 240Wh/mi is based on Tesla's estimated 310 mile range although a lot of people get better range.
So if you take the inverse of that you get the miles per kilowatt. In this case it is 4.167 kW/mi

How can I calculate my cost per charge? I certainly know how much PSEG is charging me but as stated above I don't know how much a charge utilities. Again, I only have the Trip stats.
This is based on what your utilities charge you. Just multiple your rate with the kilowatt you used.
Example: Utility rate is 10c/kW. If you used 60kW for a trip, then your cost to replace that 60kW is 60 * .10 = $6.

neil.weinstock | 7 augustus 2018

Friendly reminder: the relevant units of *energy* are Watt-hours (Wh) or kiloWatt-hours (kWh). Not Watts or Kilowatts, which are units of *power*.

jamey.winchester | 7 augustus 2018

+1 Neil

CST | 7 augustus 2018

Also keep in mind that you could be losing around 10% of the energy during the charge cycle in lost efficiency of the components.

Patrick | 7 augustus 2018

FWIW I recently went through this exercise with help from others on the forum and it’s all quite simple when you net it out. As stated above the M3 with 75 KWH long range battery and normal driving will operate at about 4 miles per KWH or 250 wh/mile. Filling up the tank costs an average of about $10 in most parts of the US, vs about $40 per tank on similar ICE sedan.

All this with unprecedented performance, amazingly cool capabilitiies and extreme comfort.

Gotta love those numbers!

BEHAR.ETHAN | 9 augustus 2018

Thanks all I believe this should be enough! Ya'll are great!

jefroman | 28 november 2018

Does any of this matter if I don't pay for charging cost cause my employer pays for it cause I charge at work for free?

CUICE | 28 november 2018

The car displays watt-hours per mile. Take the reciprocal of that to obtain miles per watt-hour. Multiply by 1000 watts per kilowatt to obtain miles per kilowatt-hour.

grahambutton960 | 14 oktober 2019

Is there a app you can use to see your Miles per KWH

calvin940 | 14 oktober 2019

The interface shows you that.

jrweiss98020 | 14 oktober 2019

Or, if you can "do the [simple] math", about 4 mi/KWh: 310 mi range / 75 KWh battery ~=4

You'll see lots of variation on short trips. On average, 4 is a good number.