Have you ever seen the fuel economy label on a vehicle for sale? Maybe you’ve heard things about the range of an electric vehicle (EV) and wondered how accurate it is? Recently, the Australian Automobile Association (AAA) has been conducting ‘real-world’ testing of vehicles, which is useful for New Zealand as we have similar vehicles.
After each batch of tests, the results are reported by media – usually highlighting which cars didn’t measure up to expectations. Either an EV has failed to live up to its claimed range, or a combustion car is using more fuel than advertised.
But can these tests teach us anything, or are they simply headline grabbers?
Internal Combustion Engine (ICE) vehicles have a fuel consumption rating. This is measured in litres per 100km and helps compare running costs and emissions.
Battery Electric Vehicles (BEV) list ‘range’: This is how far the car will travel on a single charge. (EVs also have a consumption rating: how much mains-charged electricity the car consumes per kilometre).
Why aren’t ICE vehicles tested for range? Because petrol pumps are everywhere and easy to find, most drivers don’t worry about where they’ll refuel.
EVs are different. While most charging happens at home, regional road trips require pre-planning. The driver needs to identify convenient charging locations (preferably near a good café and toilets) along the planned route. An understanding of an EV’s maximum range helps this process.
Most real-world tests have shown the vehicle’s actual performance to be different from the claim. But should we be concerned? Or can a little understanding give us more realistic expectations of a car’s performance?
New Zealand uses a vehicle test called WLTP. The test puts a car on rollers and follows a specific speed-time plan. It has sections for low speeds and some higher speed driving. Wind and temperature are controlled and are identical for every test.
These lab tests are great for comparing vehicles with each other. But the moment a vehicle is out on the road, things are different.
It’s cold or hot. It rains. The wind blows (or doesn’t). We have hills, rough roads (New Zealand has a lot of coarse chip seal), or maybe you drive a certain way.
None of those conditions are perfectly repeatable even if you drive an identical route.
The idea of ‘real-world’ is slightly flawed because it is subjective: your real-world or my real-world? My driving might consist of a supermarket visit, the school run and the odd weekend trip. Your driving could be a daily 80-kilometre motorway commute.
Both of those driving scenarios have different energy consumption profiles. While no two real-world tests can exactly match each other, they can be helpful.
The test in Australia covers a 93km circuit with one third urban, one third rural roads (70-80km/h) and one third motorway (100km/h). It tells us how a particular vehicle will perform on this kind of driving route.
For example, one EV might do better than another (it could have better aerodynamics). Or maybe one combustion model does better on low-speed roads than another.
In all vehicles, energy consumption rises at higher speeds due to aerodynamic drag. This effect is especially noticeable in electric vehicles, which are highly efficient at urban stop-and-go driving. An EV recovers energy when braking or slowing down, converting it into electricity to recharge the battery (known as ‘regen’).
In contrast, an ICE car loses a lot of energy in urban stop-and-go driving – which increases fuel consumption.
Because lab tests have a minimal amount of highway driving, the claimed EV range is very optimistic if you are doing road trips.
Sure enough, the AAA’s first batch of EV real-world tests showed all vehicles fell short of the claimed range. This is not unexpected as the test route has more high-speed driving than a lab test.
On the same route, 77% of combustion cars used more fuel than claimed.
If you’re considering a new car, the more research you do, the better. Taking real-world tests into consideration can help set realistic expectations. Explore further; see Australia’s real-world tests, check fuel economy at rightcar.co.nz, or check an EV’s range (and suggested real range) at evdb.nz
