Hi Oakville, Our worst range reading we got during testing was with the Heater on Medium setting fan on I think 3/4 full and traveling at about 90 Km / Hr up hill on a slight gradient from 100 Ft to 500 Ft Above Sea Level over 49.7 Km.
Trip time was about 45 minutes so the heater was only on for 45 minutes and based on the readout on the power meter on the dash, it was constantly going on for a few seconds an then off for 10 sec. I guess this would mean it might be on for an unknown amount of amps for about 1 / 3 rd of the trip time so 15 min on max would be the equivalent, maybe ?.
We used 10 Bars out of a full 16 bars, and had to refuel at a friend's house for about two hours on 240 Volts at about 9 amps for the trip back, which gave us about 4 bars back for the tank for an in tank level of 10 bars, and we came home on no heater for most of the trip, and arrived with two bars left.
We calculate the expected range with two people, heater on medium, outside temp about 16 C, at 90 Km / Hr would have been 50 Km / 10 bars = 5 km per bar, so from full to flat it would be 16 bars x 5 km = 90 km range.
The trip was up hill on the way there and downhill a bit on the way back and we usually see better fuel economy on the petrol car on the way back compared to the way there.
In testing later without heater or aircon, at 100 Km/Hr, we calculated the difference between up hill and down hill is about 2 bar usage so not bad. In the car it is about 2 litres per 100 Km for the up hill or about one litre more used for the trip uphill in the V8. We used 9 bars there and 7 bars back, including the Turtle mode, for a total of 100 Km. One person only.
I would expect that at 100 Km / Hr, with Heater on Max, Range would be about worked out by a combination of trip time as the heater is drawing a steady load at max, and a varible power amount from the car motor.
Assuming constant speed at 100 Km / Hr with one person on board for 100 Km no heater or aircon uses 100 km range/ 16 bars = 10 km per 1.6 bars or 160 watts / hr per 1 km.
The Heater uses approx 5.5 Kw per Hr so if we work out the time taken per km at 100 km per hour for the trip we would get a rough idea of the heater on time and usage of power for the trip.
5, 500 watts / 60 minutes = about 92 watt hours per minute.
So if we do it in 10 minute stages it wuld be approx:
Car would travel in ten minutes approx 17 km. using approx 160 watts x 17 km = 2,720 watts.
Heater would use in Ten minutes approx 920 watts.
For a 65 Km trip, at 100 Km / Hr this would take approx 10, 400 watts for the motor and about 39 minutes of travel so the heater would be on max for about say 40 minutes. One could also turn on the heat 5 minutes before leaving and off 5 minutes before the end of the trip for the same power usage I think.
The heater usage at 40 minutes is 92 x 40 = 3, 680 watts.
The total trip use for 65 Km is 10, 400 + 3, 680 = 14, 080 watts or about 14 bars.
You would have about 2 bars spare. But at 70 Miles per hour, which is about another 17 Km / Hr faster I think, The trip time would be a bit shorter but motor power usage more, but also heater usage slightly less.
I think it should work.
Bear in mind the time stuck in traffic or gong slower, would increase heater on time and reduce motor power use.
I would say that if you preheated the car to hot while plugged in or via a plug in fan heater before on the trip to work, and ran the heater on Medium on the way to work, you would have more than enough to have the heater on max on the way home, but if possible to give some reserve, I would turn the heater off or to low for the last five minutes of the trip, saving 92 x 5 = about 500 watts or half a bar.
That would give another 2 km or so ! Off for the last ten minutes and it would give another one bar or 5 km which might help.
If someone could make up an app or sliding rule for working out likely range with aircon and or heater, at various speeds and loads, it would be easy to then plan a trip and know how much spare we would have.
I think a spare two bars in reserve is best.
inputs I use are:
heater on medium, 90 Km hour two people on board = approx 5 km per bar.
Motor power use one person on board, no heater or aircon at 100 Km / Hr = 160 watts per Km travelled.
Heater on max while not moving or at slow speeds, heater power only = 92 watt / hrs per minute.
Air con Is I think 4.4 Kw / Hr so about 74 watts / Hr per min.
Motor use only, no air con or heater, at 100 Km / Hr = 160 watt / Hrs per Km
So if you know the speed, time taken for the trip, load carried and heater or aircon setting, one can estimate the likely usage and say yep i can do this with reserve or maybe do it or might be a bit tight so no aircon for the last few miles in case.
Experience is the best thing though, choose a non stressful time to do the test, like a weekend not when you are running late for work, Grin, and have a back up plan for recharging or a portable 240 volt generator, and go try the trip out with first of all, no aircon or heater, to get an idea of real usage at the speed one expects to travel at and in traffic conditions similar to expected.
On a hot day take a portable battery powered fan or on a cold day dress up warmly like you would walking outside. Hot water bottle or 12 volt electric blanket with the heat seat on !
If the testing shows only 9 bars used on no air con or no heater trip, should be fine with the heater on Max, a few bars over, 9, might be a bit tight.
Try the no aircon and no heater first for confidence, then try the heater only, on the way home, if it looks iffy on the range meter you can always turn the heater off. If you test the heater on max on a moderate day, you can always leave it on max and wind down the windows to compensate.
Note the wind buffet if the windows not synced right, I had to experiment to get the wind buffet down to an acceptable level, but find this in our other cars too.