A community experiment to measure the effects of ‘Eco’ and ‘Drive’ settings in Nissan Leafs

Your Take home messages

The ‘Eco’ setting increased efficiency (km/kWh) and range of ‘Generation 1’ Nissan Leafs by approximately 2.9% during summer.  This could provide an important safety buffer of around 3 or 4 km extended range for long trips away from base by a 24 kWh Leaf, but it delivers a minimal gain in practicality for local everyday travel.  Choosing the Eco mode saves an average Leaf driver around $1 in electricity costs per summer month, but reduces the pleasure that some drivers gain from the increased responsiveness of the vehicle when in Drive mode.  Future research could usefully measure the efficiency gains from Eco mode in winter, and from a mixed strategy throughout the year in which Eco is selected for downhill and stop-start conditions, but Drive is selected for flat and uphill travel and when steady momentum is expected.

Why was this experiment done?

The maximum range of an electric vehicle is determined partly by propulsion efficiency (km/kWh) and partly by battery energy holding capacity when fully charged.  Range is an important determinant of the vehicle’s utility and associated “range anxiety” of the owners, especially for the early and relatively small electric vehicles, like the Generation Nissan Leaf[1] [superscripts link to ‘Endnotes’ listed in the last section of this report].  By March 2018, there were 3245 Nissan Leafs registered in New Zealand, and their number is approximately doubling every year[2]. Some of the earliest Gen 1 Leafs now have 70% of their original battery holding capacity remaining[3], so any mechanism for increasing their maximum range between charges is particularly important.

One way that a driver can extend the range is to select the ‘Eco’ setting on the dashboard rather than the ‘Drive’ setting.  In the 2011/12 variant of the Leaf, this damps the accelerator pedal and increases the amount of energy that is ‘regenerated’ (i.e. stored back in the battery) as the car slows or brakes[4].  In the 2013-16 variant, the cabin climate control mechanisms are also curtailed to reduce energy consumption even further.  Some models also have a ‘B’ setting which increases the capture of the regenerated energy[5].  Nissan research claims that the Eco setting will “increase of fuel efficiency on the order of 5% to 10% depending on driving conditions” [3].

A group of Dunedin-based Nissan Leaf owners[6] set out in November and December 2017 to:

• Record their normal use of the ‘Eco’ and ‘Drive’ efficiency setting
• Record how different the driving experience was when using the ‘Drive’ and ‘Eco’ settings
• Measure the change in efficiency and range triggered by using the ‘Eco’ setting in summer conditions
• Recommend when to use the Eco and Drive settings and further research to identify strategies for improving range in future.

Methods

All participants in this experiment had signed up to Flip the Fleet, a coalition of electric vehicle owners that upload monthly data to a communal database in order to measure the performance of electric vehicles throughout New Zealand (www.flipthefleet.org).  A letter to Nissan Leaf and eNV200 owners from Otago in October 2017 identified 30 volunteers to take part in a switch-back experimental design in November and December as follows:

1. Participants were randomly assigned to driving in either Eco or Drive mode in November, and then to switch to the opposite mode in December. They were asked to just maintain their normal use of B mode if it was available in their model.
2. At the start, at half time, and at the end of the experiment the participants recorded (i) their average efficiency (km/kWh), (ii) distance travelled (km) during the month, (iii) the proportion of travel that had been in an urban speed restricted zone, and (iv) their average speed(km/hour) as recorded on their dashboards. They were also reminded to reset the meters for the next month.
3. Drivers were asked (i) about their normal use of the Eco and Drive settings before the experiment began and why they chose either setting, (ii) their predictions of what we would find, (iii) how it felt when they changed settings, and (iv) having completed the experiment, what mode they would use in future.
4. All participants were asked at the end of each month to confirm that they had (i) maintained their assigned ‘treatment’ throughout each month, (ii) remembered to switch their treatment at the change-over point, (iii) reset their efficiency and speed meters at the change-over point, and (iv) maintained their unusual travel in the two months so that might have disrupted the comparisons.

Lapses in the protocol, unusual travel, and incomplete data forced the elimination of all but 21 paired comparisons of efficiency in Eco and Drive settings[7]. The retained sample included two owners who had each taken a long trip to and back from Christchurch, but where the meters had been reset before/after each leg of the trip.  In both cases, the drivers selected Eco for one leg, and Drive for the other, so we included the Christchurch trip and normal travel around Dunedin as two separate replicates of the experiment[8]. One driver was from Wanaka, the rest were based in Dunedin.

A statistical model[9] was constructed using the Genstat statistical software package[10].

Results

Previous use patterns

Of the 21 participants who reported their normal use before the experiment, only three (14%) used Drive for nearly all the time (99 – 100%).  One participant used Eco about the same amount as Drive (50%), and another used Eco 70% of the time.  The remaining 16 (76%) of participants used Eco mode for 90% or more of their travel[11].

Of 23 drivers that started the experiment, 11 had a ‘B’ mode setting available.  Five of them used the B mode for over 90% of their travel, two for 80% of their travel, and the remaining four used it less than 5% of the time.

The reasons reported by drivers for use of the Eco mode were that it was more economical[12], particularly in hilly conditions[13] or when using the heater[14], to avoid fast charging when visiting town[15], to avoid rapid acceleration[16], to constrain speed[17] and to make less use of the brakes[18].  Some that mostly used Eco considered that the lower speed and responsiveness were still perfectly adequate in their normal driving conditions[19]. The Drive mode is used sporadically by some drivers (who normally use Eco) to climb hills, put a distance between trailing cars, or simply to “show off”[20].  Some drivers who regularly use Drive like the speed and faster pick-up[21].  One family considered that their use of Eco was just a habit formed when they first got the Leaf and were more worried about range[22], and another deliberately uses the Drive mode to learn about the car’s performance by experimenting[23].

Drivers’ reactions when switching modes for the experiment

Some participants noticed that the selection of the Eco or Drive setting led them to change their driving style in response[24], or at least to think differently about the way they drive[25], but one participant thought that she/he did not alter their driving style at all[26].

Some participants commented that they comfortably adjusted to the ‘new setting’[27], even though it did indeed feel quite different at the start[28].  Drivers reported that the ‘Drive’ setting felt “looser”[29], more “responsive”[30], and for some drivers more “fun”[31].  For some participants, the Eco mode reduced range anxiety and encouraged more efficient and eco-friendly driving[32].

Some participants were surprised, and some were disappointed, that there appeared to be less gain in efficiency from using the Eco mode than they expected[33].  Some hypothesised that the warmer weather and light traffic conditions during the experimental period raised efficiency, so the balanced experimental design was important for disentangling the Eco/Drive setting from month effects[34].

Future driving modes after the experiment

Some participants decided that they would switch to mostly using the Drive setting from now on in order to enjoy the car’s improved responsiveness[35].  Others were content to remain using Eco mode after the experiment, partly because the performance was more than adequate, or that they valued the continual reminder to be energy efficient[36]. Others resolved to use the Eco settings when driving in town, and Drive in hilly country or when out on the open road[37], or to use Eco only when it was needed[38]. Others wanted to wait for the results of the experiment were collated before they chose their future driving mode[39].

Predicted change in efficiency

Aside from repeated general predictions that Eco mode would improve efficiency overall, some of the participants made more detailed predictions about what the experiment would show: Several thought that the difference in efficiency would be small[40], but some thought that a 10 km,[41] or at least a 10 % increase in range would be achieved when driving in Eco[42].  Two participants identified weather and season as important effects because of the way Eco reduces energy demand of the cabin’s climate control systems[43].  Eco was expected to lift efficiency more in stop-start conditions of urban driving, and where the terrain is hilly[44], and overall to have less effect if the driving is at a steady in pace.  Two participants predicted that Eco’s effect would be reduced at higher average speeds because open road travel is steadier (and so there is less advantage of regenerative braking) [45]. One driver predicted that load would affect the difference between Eco and Drive, but she/he did not specify in which direction the change would occur[46].

Observed change in travel and efficiency

There was no sign that the Eco/Drive setting altered the distance travelled during each month of the experiment[47], as expected if the participants maintained their normal car use patterns for both treatments (Table 1).  Also, statistical modelling could detect no difference in changes of travel efficiency between treatments when the Drive treatment fell in November compared to in December[48].  The national Flip the Fleet data gathered throughout the experimental period also showed virtually the same average efficiency in the two months[49]. These comparisons suggest that external conditions (weather and travel patterns) have not greatly disrupted the experiment. A relatively crisp partitioning of the two experimental treatment effects can therefore be expected from the “switch-back” experimental design.

 

Table 1: Average travel distance, speed and efficiency during each month of travel using the Eco and Drive settings in Nissan Leafs[50].

Average speed of travel of the participants were very similar between the treatments (Table 1), and months.  However average speed decreased by 0.21 km per hour for every 1% increase in the proportion of driving that was within the urban restricted speed zone[51].

Selection of the Eco mode led to an average increase in efficiency of 0.29 km/kWh compared to using the Drive mode.  However, the ‘95% confidence interval’ for this difference is wide (0.08 – 0.34 km/kWh), so the study has only provided a very imprecise estimate of the efficiency gain from selecting Eco mode.  When expressed as a percentage gain compared to the efficiency in Drive, the Eco mode is estimated to have increased efficiency by 2.9%, but the 95% confidence interval suggests that this could have been as low as 0.8%, or as high as 5.0%.  The statistical model could find no significant association in the size of this effect with month of the treatment, average speed, or % of travel that was within the urban restricted speed zone[52].

 

Discussion & Conclusions

Elimination of vehicles with incomplete data or disrupted treatments reduced the expected sample of 32 for the experiment to just 21 paired comparisons of performance in the Eco and Drive treatments. This severe elimination of data was necessary considering the inherently variable observations of the treatment effects that we observed.  Clearly many other factors affect the size of the change in efficiency when switching between Eco and Drive.  Predictions of the participants before the experiment suggest that individual driving style, speed, load, and especially a smooth driving pace are important determinants of treatment effect size.  Cross-checks for unusual travel, distance and speed changes between months, and the balanced switch-back design that started half the cars in opposite treatments in November, suggests that maximum control of weather and month effects was achieved. Nevertheless, a much larger study will be needed to narrow the uncertainty in effect size.

This experiment was done in early summer.  A much larger treatment effect might be expected in winter when the Eco mode suppresses the energy drain of cabin climate control, and when wet driving conditions and overall efficiency of travel is much reduced.  The national Flip the Fleet database estimates average efficiency of 6.25 km/kWh in July compared to a peak of around 7.0 km/kWh in January.

A lift of 2.9% in efficiency (0.8% – 5.0% confidence interval) was lower than expected by some participants, but consistent with Nissan’s own estimates as revealed from the range predicted by the ‘Guessometer’ on the Leaf’s dashboard i.e. increased range is predicted when switching from Drive to Eco.  Ten such measures across a full range of ‘State of Charge’ revealed a 4.1% increase in range when Eco was selected[53].  This is lower than the a reported “increase in fuel efficiency on the order of 5% to 10 % depending on driving conditions, according to Nissan’s research” [3]. However, there is no detail of the method or source of this assertion, and despite a large number of blogs in the internet about the use of Eco and Drive settings, there are no quantitative estimates of the size of any effect or descriptions of experiments like the one done here by Dunedin Nissan Leaf owners. Assuming that the gain is approximately 2.9%, and that the Leaf is driven at the national average efficiency for November and December (6.9 km/kWh), selecting Eco will provide an added maximum range of about 4.4 and 3.1 km for a 24 kWh Nissan Leaf with 100% and 70% battery State of Health respectively[54].  On average, Nissan Leaf owners spend around $36 per month on electricity to power their car[55], so the 2.9% gain from using the Eco setting equates to saving around $1 in each summer month.  Selection of the Eco mode therefore has a small impact on reducing costs and extending range in normal driving conditions.  Most trips away from base are well within the maximum range of the Nissan Leaf, even one with a 70% battery State of Health[56], so in normal driving selection of the Eco setting makes little practical difference.  A secondary advantage of using the Eco setting will be prolonging the life of the brakes.

One participant was sceptical that we would be able to identify the causes of any differences we might observe, specifically because we cannot separate the mechanical effects of the setting from the shifts in behaviour of the driver when using the different modes.  She/he said

“We have to be careful about assuming that the effect, if any, is caused by the mechanics of the setting alone – people may flip into Drive mode for a speedy thrill, or being in Drive may encourage faster driving – so driving style may vary with mode – dialling up experimental treatments should minimise this effect, but it may not eliminate it and the results that we get may not actually reflect the actual difference in efficiency seen when outside the experimental period the drivers choose Drive mode.”

Accordingly, our estimate of the 2.9% gain from selecting Eco mode may not translate directly to an estimate of its effects across the board, especially if drivers only select it when there is a particular need or driving condition.  One potential strategy for increasing the gains in efficiency is to select Eco mode when going downhill and Drive when climbing hills or travelling on a flat.  The improved energy regeneration on the downhill will be assisted by gravity and momentum on the downhill sections, and then the loss of efficiency while using Eco on the uphill and flat sections will be avoided.

Our survey before the experiment suggested that around three quarters of Leaf drivers are habitually using the Eco mode for everyday travel, around 10% are staying in Drive for most travel, and 15% have a more intermediate behaviour of varying their use according to driving conditions and terrain.  Several of the participants were pleasantly surprised about the feel of the car when in Drive mode, especially from its improved responsiveness, when they switched from their more habitual use of Eco.  Apparently, many of our participants had simply assumed that the Eco mode is more economical rather than measured it. When combined with their surprise about how little improvement in efficiency resulted from the Eco mode, some declared their intention to switch to mainly using Drive mode in future.

It would be helpful to repeat this experiment in summer with more participants, and to do it in mid-winter to measure the value of the Eco setting when maximum range is most limited.  It would also be valuable to measure the gain from of a ‘mixed’ strategy where Eco is selected on downhill slopes or stop-start conditions in town, but Drive is used on flat or uphill sections and in open road and motorway conditions where traffic flow is steadier.

Despite its minimal effect on efficiency during normal local travel, the Eco mode could be critically important during occasional extended travel away from base – indeed it could make the difference to get home or to reach the next rapid charger.  Our study suggests that despite its ‘Eco’ label, drivers need to be realistic about this option.  At least in summer, selecting Eco only provides a minimal safety buffer and a much smaller extension of range than can be achieved by driving more slowly and steadily, and from switching off air conditioning, heaters and lights.

 

Henrik Moller

4 April 2018.

 

Acknowledgements

This experiment would not have been possible without the enthusiastic and active engagement of the following participants: Alistair Madill, Andrew Last, Andrew Smith, Anthony Reeder, Chris Ford, Craig Nieper, Craig Proctor, Dave & Lois Edwards, Edwin van Broekhoven, Garry Kyle, Henrik Moller & Fiona Stirling, Hugh McLean, Jacqui Dickson, James Brundell, Kelvin Lloyd, Leonie Rousselot, Nick Blennerhassett, Pam & Tom McKinlay, Peter Cheyne, Rayna & Mark Dickson, Simone Bray, Simonne Wood, Stuart Hebberd, Tim Ross, Vicki Booth, and Xuan Luo.

We thank Otago Museum’s “Science into Action” team that provided part of the funding to build and test the Flip the Fleet programme in late 2016 and 2017. The remainder of the funding was provided by Ecosystems Consultants and PowerStats Ltd.

 

References

Ford, R., Stephenson, J., Scott, M., Williams, J., Rees, D., & Wooliscroft, B. (2015). Keen on EVs: Kiwi perspectives on electric vehicles, and opportunities to stimulate uptake (Working Paper). Centre for Sustainability, University of Otago.

Ivanov, D., & Moller, H. (2017). “Getting stranded by running my battery flat is a real worry for me” 1-Click Survey # 9 https://flipthefleet.org/2017/getting-stranded-by-running-my-battery-flat-is-a-real-worry-for-me-1-click-survey-9/

Myall, D.; Ivanov, D.; Larason, W.; Nixon, M.; Moller, H.  (2018).  Accelerated Reported Battery Capacity Loss in 30 kWh Variants of the Nissan Leaf. Preprints, 2018030122 (doi: 10.20944/preprints201803.0122.v1).

Endnotes

The superscripts in the text denote the following sources.  Direct quotes from the participants responses to the mail before, during and after the experiment are italicised.

[1] Ford et al. (2015), Moller & Ivanov (2017)

[2] www.transport.govt.nz/research/newzealandvehiclefleetstatistics/

[3] Myall et al. (2018)

[4] www.livingleaf.info/2011/09/what-does-the-eco-drive-mode-really-mean-on-the-nissan-leaf/

[5] www.livingleaf.info/2013/06/2013-leaf-eco-and-b-mode-sv-and-sl-trims/

[6] The sample also included one eNV200 Van

[7] The one eNV200 van that participated was eliminated from the statistical modelling because it was an extreme outlier and had taken an unusual trip out of Dunedin in one of the months.

[8] Some of the volunteers in this experiment also participated in the community experiment i9n November where load was manipulated in a day trip to an EV community gathering at Waitati (see www.flipthefleet.org/2017/effects-load-eco-stetting-route-efficiency-dunedin-ev-community-experiment/).   The meters were reset before and after this load experiment so that the effects of this unusual travel could be separated from the main results.

[9] These were REML ‘Mixed Linear Models’ in which Mode (Eco/Drive), Month (in which Drive was selected), and % of travel in urban speed restricted zones were the fixed effects.  The vehicle’s identity (Registration plate) was a ‘random effect’, so that the specific influences of a family’s driving style, terrain and condition of the vehicle were factored out of the analysis as much as possible.

[10] VSN International, Version 19.1 www.vsni.co.uk/

[11] Seven estimated their use of Eco as 99-100% of travel; six as 95% of the travel, and three as 90% of travel.

[12] “I assume it’s more economical” ● “Attempting to be as economical with energy as possible” ; “Far better regenerative function in Eco”

[13]  “I occasionally switch to Drive when ascending a steep hill” ● “I live in the Dunedin hill suburbs, so there is a lot of driving downhill” ● “Feels like I get better regen on hills and I want to maximise range” ● “Drive will be more inefficient in that the “sporty” responsiveness will mean I accidentally accelerate more than I need to and will brake more. Plus I will lose the regeneration I get from driving down the hill from my house each day. I don’t charge to 100% each day so I will regenerate on leaving in the morning”

[14] “I tend to stick to Eco (but if in D, then will usually drop back to Eco going down hills or if using heater”

[15]  “I want to preserve the power so I won’t have the need to recharge in town. I haven’t done so once since I got the car in May 2016”

[16] “We use Eco mode so the car is predisposed to accelerate slowly”

[17] “Eco mode means slower driving, hence less drain on the battery”

[18] “I use Eco to get slightly better range from more regeneration and less use of the brakes”

[19] “Nearly all my journeys are flat and in 50kmh or windy roads, so Eco perfectly adequate” ● “Eco is still amazingly grunty, fine for around town, good enough on hills etc, and I presume it’s more efficient (I have yet to assess).  D is great for sudden surges/overtaking, but I have not really felt I had to use it”

[20] “I rarely switch to ‘Drive’. But if i do it will be to dart out into traffic, go up a steep hill, or get rid of someone tailgating….or, yes I admit…to show off!” ● “In Eco mode believing that I am saving battery power and the performance matches any car of its size on the road. I must admit I sometimes give it a quick burst in Drive to convince the car behind that EVs do not drive slowly”

[21] “The assumption that Eco conserves the charge better, but we would prefer the “peppiness” of driving in Drive”; “Tend to not use Eco mode as it dulls the throttle response”

[22]  “Habit.  When we got the car we weren’t sure about how far we could on one charge. We thought Eco mode would give us more range.  Now we just keep it on as we usually just drive into town from Waldronville and back or to Mosgiel.  Either way has a steep hill in the way but most trips to town avoid the motorway”

[23] “Mainly have been switching occasionally out of curiosity – i.e. deliberately varying the settings and use of accessories to monitor effect – we log all our standard trips (airport, Tūmai) for this family experimentation”

[24] “Probably consciously slowed down and watched speed… too easy to go over the 50kph limit in town when in D” ● “I found myself more conscious of efficiency and actively trying to minimise the effect of being in Drive, but maybe that will be more of an imaginary problem?” ● “In Eco I tended to drive normally whereas in Drive I got a bit more enthusiastic….”

[25] “Certainly, when coursing down a hill one realises that there one is wasting a lot of energy – but then I also notice that we go faster downhill – so does the amount of recovered energy not change that much altogether because of momentum i.e. faster travel so perhaps faster recharging vs less time going down hill??!  It’s a mystery and this was an interesting experiment” ● “I feel better for the assumed environmental benefits when in Eco B. It feels less caring, more aggressive and at times fun when in Drive”

[26] “I would have driven the same in both modes”

[27] “By the end of the month, driving in D felt as normal as driving in ECO had previously (as a mainly ECO mode driver)” ● “Felt fine – you quickly get used to what seems less powerful than Drive, but because Eco is still great torque, it’s plenty for all the driving I did.  Lots of hills, and in Eco the car still drove them beautifully.

[28] “In Eco mode the acceleration of the van is significantly reduced. I feel that you end up pushing harder on the accelerator just to keep up with the general traffic speed. Our kWh/100km was higher than previous months??

[29] “The car feels “looser”.  Certainly more peppy – I contacted my inner hoon every now and then” 

[30] “Driving in B Drive mode feels nicely responsive and breaks a bit when going down hill or slowing down, which is great, as that power goes back into the battery”

[31] “We have always driven in eco mode from taking ownership in July 16, so the increased responsiveness/sportiness of the drive mode was interesting. More fun” ● “Driving in eco feels like you have less power” ● “[Drive is]Much more responsive. I actually quite liked it. Quicker acceleration at traffic lights, crossings etc.” ● “The car was peppier especially on hill climbs – more responsive”

[32] “Driving in eco mode gives us instantly more km on the guessometer, which feels good to start off with and probably inspires me to drive a bit more conservatively to try and get more distance. It also feels like it slows the car down a bit going uphill”

[33] “Drive mode was more fun.  It possibly uses more power but not as much as I thought”

[34] “The average consumption [in Drive] of 13.8 kWh/100 km was less than I thought it would be…however I notice that so far this month it as around 12…again, lower than I thought…but all this may be due to the unusually warm ambient temperatures improving battery performance”

“To start with, I was surprised how efficient Drive seemed to be – we were getting better efficiency than the previous month (we normally drive in Eco). However, I now think that this was to do with the external temperature being better so giving better performance – it is even better now we are back in Eco.

Surprised that Drive mode (December) led to record efficiency. For our drive (very light traffic & few stop lights) decelerating in Drive mode is sufficient to slow into corners without braking.

[35] “In general, I liked driving in D. Occasionally I missed the higher regen that you get in ECO.   I think I’ll go back to mainly D again in January and then just use ECO when the extra regen is wanted or to reduce the heater consumption in winter.  But first it will be interesting to see the results!” ● “Good. Feels more sporty but at the same time my economy figures are as good, if not better, than ‘eco. I now prefer to drive in D mode” ● “Liked driving in D mode. Really liked the lighter feel of the accelerator pedal. Economy didn’t seem to take a hit. Reached Moeraki with 44% remaining! Best ever for me. Using B mode at times helps to. Don’t think my driving style has had a mode change as well but those zippy take offs in town are fun! From now on D is the mode for me” ● “In terms of what the drive feels like, there is a certain easiness about Drive which is pleasant, but the power of Eco is perfectly adequate for driving around town, even up hill, so I wouldn’t bother to use Drive often (except sometimes going up a steep hill)” ● “Accelerating slowly & maintaining momentum in Drive mode seems more efficient than the regen in Eco mode & subsequent need to accelerate harder out of corners. The car is much more dynamic in Drive mode compared to the sluggish acceleration in Eco mode. I much prefer Drive mode, in Eco I tend to drive like a cautious octogenarian” ● “Definitely more sluggish in Eco; I found myself less concerned about efficiency, thinking it would take care of itself when in Eco; But I also think that my November Drive period seemed very efficient, so I’m likely to use Drive a lot more now – perhaps very different in winter?”

[36] “Prefer Eco, no need for the extra acceleration etc in Drive mode” ● “I felt as though I was driving a sportier and more responsive car when in Drive Mode. I was tempted at times to make use of the seemingly better acceleration but I have now switched back to ECO Mode and even if this mode is not genuinely more economic, it is a constant reminder to drive in an economical way” ● “When you’re constantly just using one setting, as we were for the experiment, there were no noticeable differences, as Eco mode is still gutsy enough for hills and all travel. When you switch between the two though, like now that I’m back to doing what I like, you can definetly feel the extra power in the Drive mode.  Because I don’t feel it particularly necessary however, I would probably just leave it on Eco, if it does indeed prove to be more efficient”

[37] “Climbing hills use drive and eco going down. Urban running – Eco”

[38] “In the end I didn’t really notice that much difference driving in D or ECO to be honest.  My preference though is now D and then just engage ECO as needed e.g. when more regen is wanted”

[39] “The different modes feel different; more braking in D mode, but no significant change in driving style. Will see what the results of the study are before I have a final preference”.

[40] “Probably the differences will be minimal” ● “It think there is going to be very little difference between the two modes” ● “If people drive moderately anyway, there should not be much difference, otherwise eco mode will give more distance, (our guess about 3% difference)” ● “I predict a minimal difference (perhaps less than 5% across the board) in summer – but it might have been higher if we did this in Winter because of the reduced heating and added friction on road and more erratic driving to keep distance etc.” ● “I predict that there will be little difference between the two modes and that by driving in an economical way the same results may be achieved in either mode. This is because changing from Eco to Drive doesn’t change a thing apart from requiring you to press the peddle by a different amount to achieve the same effect!”

[41] “Most Leafs would have a maximum range of between 100 and 140 km in summer, so an additional 10 km would most likely equate to a 7% – 10% increase in range”

[42]  “I suspect we will get another 10Km further on a charge” ● “Eco will save potentially 10-15% – why would it exist otherwise?”

[43]  “If the weather stays warm then I think D may have a slight advantage as it is more efficient to keep rolling forward than to regen.  If the weather was cold then I think Eco might have the edge due to less heating consumption (for Gen1 Leafs anyway)” 

[44] “I think the effect size will be greater in hilly terrain and in higher proportion of urban driving because of the stop/start trajectory in town and greater regenerative charging as the car slows, and more even and slower acceleration away from lights.  But overall the individual driving style may cause scatter – as long as the same drivers use the EV in both phases of the switch, this shouldn’t matter that much, but in general a careful and above all, a steady driver, may see comparatively little difference in efficiency between the two settings” 

[45] Those with higher average speeds (indicating more steady-speed open road driving) may see least difference between Eco & D” ● “Speed itself may not be a clear signal because it depends on the terrain where people go faster – trundling over the Canterbury plain at speed is unlikely to incur much slowing and accelerating, so little difference in modes?” 

[46] “I guess that a heavy load will increase the difference between modes, but we can’t test that easily”

[47] The REML model estimated that the probability that the travel distances were different between the months was p = 0.52.

[48] The REML model estimated that the probability of there being some difference in efficiency between the months was p = 0.13.

[49] The average efficiency of 191 Leafs in November was 6.90 km/kWh; and the average of 192 Leafs in December was 6.91 km/kWh.

[50] The averages and standard errors in Table 1 are the ‘Maximum Likelihood Means’ as predicted by a REML statistical model in which the car’s identity was included as a Random Effect (this removes the variation observed between vehicles to exclude terrain and driving style differences between the owners). The last column is the probability that the apparent association between the response variable (column 1) and the Eco/drive setting occurred by chance (sampling error).

[51] The standard error for the % urban effect was 0.0651 km/h, and there was very little chance that this effect occurred by sampling error (p=0.004).

[52] Month p = 0.17, % urban p = 0.87.

[53] H Moller, unpublished.

[54] The equivalent gain for a 30 kWh Leaf with 100% and 70% State of Health is 5.6 and 3.9 km respectively.

[55] Calculated from Flip the Fleet’s communal database in November 2017.

[56] www.flipthefleet.org/2017/drivers-memo-15/