Maximising efficiency and range
One of the perks of driving an EV is the instant power whenever you want it, but there are times, perhaps when you are pushing to maximise the range, that you want to drive as efficiently as you can. It is worth noting that these are suggestions, not hard and fast rules. There will be just as many people who disagree as those who agree. There are a lot of variables: it depends on how you as a driver want to drive, the terrain, the weather, the temperature, your speed and acceleration to name just a few. If you are driving lots of short journeys, especially from cold, the efficiency will take a bigger hit - just the same as an ICE. This is because the initial time taken to heat the car is a bigger percentage of the overall journey. A single longer journey is more efficient as you heat the car at the start, and it is then on tick over for much more of the journey.
KERS (Regeneration)
Although KERS is sometimes seen as purely a efficiency gain, it is worth understanding how it works, and why it can sometimes be bad for efficiency. When you drive, the battery powers the motor to accelerate. When you slow with KERS, electrical power is drawn from the motor and this slows the car down - this electricity is then fed back into the battery. If you drive up a hill and use KERS to slow your descent down the other side, the battery will get back some but never as much power as you put in to go up the hill. It will always lose overall.
Comparing this to the eco friendly rule of “Reduce > Reuse > Recycle” in that order. rather than “use and throw away”, when driving efficiently we should therefore reduce power input, before we recycle power with KERS and this is all in preference to throwing the power away with braking. The absolute ideal for efficiency is to accelerate just enough, never brake or use KERS and to coast to a stop perfectly at each junction – but this isn’t always entirely practical or possible.
GOM (Guess=O-Meter)
The car estimates your current range. It uses a few data points (battery %, outside temperature, recent driving efficiency, car driving mode and HVAC setting) to estimate how far you can drive, and this range is constantly updated as the battery runs down. It is an educated guess, it is unlikely to be 100% accurate all the time, it can’t possibly know if you are suddenly going to drive less or more efficiently, or if you are going to drive into a headwind.
Which settings?
How you drive is significantly more important than the car’s settings, but there are things you can do. Electric MGs have:
3 drive mode settings (Sport, Normal and Eco)
3 KERS settings. (1 – low, 2 – medium and 3 – Strong)*
MG Pilot/Automatic Cruise Control (ACC)**
*It is also possible to override KERS and run in KERS 0 – we will explain how lower down.
**MG Pilot/ACC is available in both ZS Excite and Exclusive, + MG5 long range (but not the standard MG5) – the latter having the added bonus of working alongside KERS rather than using the brakes to slow the car if it is over speeding.
I just want to drive!
If you just want to drive the same as before you bought an electric then the following basic rules can be used:
City Driving: If you are mainly doing stop/start driving with lots of junctions such as a city, then consider Eco 3. This will maximise the power regained from lots of accelerations - try to learn to allow the KERS to slow you. Avoid using MG Pilot/ACC to drive as this will use brakes only, and so KERS never regains any power. *MG 5 exclusive long range does support KERS in this mode.
Motorway Driving: If you are doing motorway or long distance driving without stop/start traffic, then you want the KERS to 1 (or 0 – see below) this will mean you can accelerate to speed and coast as far as possible without the KERS slowing you too much – whenever it slows you down, you will need to re-add that power back in by accelerating again.
Automatic Cruise Control/MG Pilot
If your car has ACC/MG Pilot, this will generally be less efficient than the most efficient driver. But it does make long journeys less stressful. The efficiency difference on motorway cruising with ACC/MG Pilot between ECO/Normal/Sport is minimal, the main difference is how hard the car accelerates again after it has been slowed down by another vehicle in front. Once it has reached a speed there is almost no difference between them.
KERS 0
As mentioned above, it is possible to disable KERS when you use cruise control. This is most useful for motorway cruising, as it allows you to coast over longer distances using less power. When you first activate cruise control it defaults to keep you driving at the speed you are currently driving at (lowest is 20 MPH). For this trick to work, you need to have activated it at a low speed, and then manually with the accelerator pedal accelerate through that speed and beyond. Once you are at least 10 MPH above the speed you set, KERS doesn’t try to slow you down again. Don’t use the KERS +/- buttons to change the speed it is set to, as then it will try to slow you again. Assuming you have the ZS Exclusive/5 Long Range Exclusive, the automatic braking will still kick in and slow you down if you catch up with other cars in your lane, (the 5 long range does this using KERS)
Heating Ventilation and Air Conditioning - HVAC
One major difference between ICE (Internal Combustion Engine- Petrol/Diesel) and EV cars, is a by product of their inefficiency - some of the waste heat can be captured to heat the car. As there isn’t anywhere near as much waste heat In an EV the heating is done electrically. It is overall more efficient than with an ICE, but it does still use battery power. When you switch on the air con, the range predicted on your car drops by about 10%. The car is making a straight calculation. In reality, running the heating on full will use a lot more power than having it set to a much milder temperature, but the estimated drop in range doesn’t take this level of detail into account. It is worth noting the heater uses less power when in eco and gives less heat. Alternatively using the heated seats in Exclusive models uses much less power. If you want to demist your windows, the air con is the quickest way by far, but if you want to maximise your range another option is to run with the window open a little rather than HVAC on, or running the air con with the heat/cool settings set roughly in the centre.
Luggage
Driving with the boot fully laden surprisingly has minimal effect on range. Whereas a roof box or bikes on the roof cause approximately 10-15% loss of range.
Speed
EVs are most efficient at about 25-30 mph (as apposed to Petrol/Diesel which is about 50-55 mph) therefore going faster will use more power. For motorway cruising if you drop to 65 MPH from 70, you will go perhaps 20 miles further in range.
Acceleration
Just like any car, the harder you accelerate the more power you use. If you try to accelerate keeping the power dial to 20% or lower (might not be possible going up hill), yes it takes much longer to get up to speed, but you use much less power overall.
Tyre Pressure
The official recommended tyre pressures are:
ZS (Unladen): 34 psi (2.3 bar) all 4 tyres
ZS (Heavily laden) Front: 38 psi (2.6 bar), Rear: 42 psi (2.9 bar) rear
5 (Unladen): 32 psi (2.2 bar) all 4 tyres
5 (heavy laden) ***need to see a data plate from a 5 for this**
Many run the tyres 2-4 psi higher that the unladen spec, which although will reduce ride comfort, will reduce rolling resistance and therefore increase efficiency.
Weather
OK, you can't change this, but it's worth understanding for planning purposes. Cold weather is by far the least efficient. Not only do you use power to heat the car interior, batteries are chemically less efficient in cold weather. You may actually see an improvement after a rapid charge, as the rapid charge process warms the cells. Lithium batteries are most efficient at about 20-25 degrees C. Wet roads are another killer: the increased rolling resistance of driving through water reduces efficiency. Driving into a head wind will take more power than a tail wind.
Final note - Charging
Although it doesn’t change your driving efficiency, if you are looking for time efficiency, rapid charging to about 80% (86% on updated ZS software) and then driving is better than trying to charge to 100%, The car is designed to rapid charge to that 80% mark, the last 20% takes about as long as the first 80% - this is common across most EVs and is done to protect the battery. (See Charging your MG page for more charging info and tips.)
KERS (Regeneration)
Although KERS is sometimes seen as purely a efficiency gain, it is worth understanding how it works, and why it can sometimes be bad for efficiency. When you drive, the battery powers the motor to accelerate. When you slow with KERS, electrical power is drawn from the motor and this slows the car down - this electricity is then fed back into the battery. If you drive up a hill and use KERS to slow your descent down the other side, the battery will get back some but never as much power as you put in to go up the hill. It will always lose overall.
Comparing this to the eco friendly rule of “Reduce > Reuse > Recycle” in that order. rather than “use and throw away”, when driving efficiently we should therefore reduce power input, before we recycle power with KERS and this is all in preference to throwing the power away with braking. The absolute ideal for efficiency is to accelerate just enough, never brake or use KERS and to coast to a stop perfectly at each junction – but this isn’t always entirely practical or possible.
GOM (Guess=O-Meter)
The car estimates your current range. It uses a few data points (battery %, outside temperature, recent driving efficiency, car driving mode and HVAC setting) to estimate how far you can drive, and this range is constantly updated as the battery runs down. It is an educated guess, it is unlikely to be 100% accurate all the time, it can’t possibly know if you are suddenly going to drive less or more efficiently, or if you are going to drive into a headwind.
Which settings?
How you drive is significantly more important than the car’s settings, but there are things you can do. Electric MGs have:
3 drive mode settings (Sport, Normal and Eco)
3 KERS settings. (1 – low, 2 – medium and 3 – Strong)*
MG Pilot/Automatic Cruise Control (ACC)**
*It is also possible to override KERS and run in KERS 0 – we will explain how lower down.
**MG Pilot/ACC is available in both ZS Excite and Exclusive, + MG5 long range (but not the standard MG5) – the latter having the added bonus of working alongside KERS rather than using the brakes to slow the car if it is over speeding.
I just want to drive!
If you just want to drive the same as before you bought an electric then the following basic rules can be used:
City Driving: If you are mainly doing stop/start driving with lots of junctions such as a city, then consider Eco 3. This will maximise the power regained from lots of accelerations - try to learn to allow the KERS to slow you. Avoid using MG Pilot/ACC to drive as this will use brakes only, and so KERS never regains any power. *MG 5 exclusive long range does support KERS in this mode.
Motorway Driving: If you are doing motorway or long distance driving without stop/start traffic, then you want the KERS to 1 (or 0 – see below) this will mean you can accelerate to speed and coast as far as possible without the KERS slowing you too much – whenever it slows you down, you will need to re-add that power back in by accelerating again.
Automatic Cruise Control/MG Pilot
If your car has ACC/MG Pilot, this will generally be less efficient than the most efficient driver. But it does make long journeys less stressful. The efficiency difference on motorway cruising with ACC/MG Pilot between ECO/Normal/Sport is minimal, the main difference is how hard the car accelerates again after it has been slowed down by another vehicle in front. Once it has reached a speed there is almost no difference between them.
KERS 0
As mentioned above, it is possible to disable KERS when you use cruise control. This is most useful for motorway cruising, as it allows you to coast over longer distances using less power. When you first activate cruise control it defaults to keep you driving at the speed you are currently driving at (lowest is 20 MPH). For this trick to work, you need to have activated it at a low speed, and then manually with the accelerator pedal accelerate through that speed and beyond. Once you are at least 10 MPH above the speed you set, KERS doesn’t try to slow you down again. Don’t use the KERS +/- buttons to change the speed it is set to, as then it will try to slow you again. Assuming you have the ZS Exclusive/5 Long Range Exclusive, the automatic braking will still kick in and slow you down if you catch up with other cars in your lane, (the 5 long range does this using KERS)
Heating Ventilation and Air Conditioning - HVAC
One major difference between ICE (Internal Combustion Engine- Petrol/Diesel) and EV cars, is a by product of their inefficiency - some of the waste heat can be captured to heat the car. As there isn’t anywhere near as much waste heat In an EV the heating is done electrically. It is overall more efficient than with an ICE, but it does still use battery power. When you switch on the air con, the range predicted on your car drops by about 10%. The car is making a straight calculation. In reality, running the heating on full will use a lot more power than having it set to a much milder temperature, but the estimated drop in range doesn’t take this level of detail into account. It is worth noting the heater uses less power when in eco and gives less heat. Alternatively using the heated seats in Exclusive models uses much less power. If you want to demist your windows, the air con is the quickest way by far, but if you want to maximise your range another option is to run with the window open a little rather than HVAC on, or running the air con with the heat/cool settings set roughly in the centre.
Luggage
Driving with the boot fully laden surprisingly has minimal effect on range. Whereas a roof box or bikes on the roof cause approximately 10-15% loss of range.
Speed
EVs are most efficient at about 25-30 mph (as apposed to Petrol/Diesel which is about 50-55 mph) therefore going faster will use more power. For motorway cruising if you drop to 65 MPH from 70, you will go perhaps 20 miles further in range.
Acceleration
Just like any car, the harder you accelerate the more power you use. If you try to accelerate keeping the power dial to 20% or lower (might not be possible going up hill), yes it takes much longer to get up to speed, but you use much less power overall.
Tyre Pressure
The official recommended tyre pressures are:
ZS (Unladen): 34 psi (2.3 bar) all 4 tyres
ZS (Heavily laden) Front: 38 psi (2.6 bar), Rear: 42 psi (2.9 bar) rear
5 (Unladen): 32 psi (2.2 bar) all 4 tyres
5 (heavy laden) ***need to see a data plate from a 5 for this**
Many run the tyres 2-4 psi higher that the unladen spec, which although will reduce ride comfort, will reduce rolling resistance and therefore increase efficiency.
Weather
OK, you can't change this, but it's worth understanding for planning purposes. Cold weather is by far the least efficient. Not only do you use power to heat the car interior, batteries are chemically less efficient in cold weather. You may actually see an improvement after a rapid charge, as the rapid charge process warms the cells. Lithium batteries are most efficient at about 20-25 degrees C. Wet roads are another killer: the increased rolling resistance of driving through water reduces efficiency. Driving into a head wind will take more power than a tail wind.
Final note - Charging
Although it doesn’t change your driving efficiency, if you are looking for time efficiency, rapid charging to about 80% (86% on updated ZS software) and then driving is better than trying to charge to 100%, The car is designed to rapid charge to that 80% mark, the last 20% takes about as long as the first 80% - this is common across most EVs and is done to protect the battery. (See Charging your MG page for more charging info and tips.)