If you’ve ever stood at a dealership squinting at labels, you’re not alone. You’ll see L/100 km, g CO2/km, kWh/100 km, MPGe, “smog” scores, Euro 6… and still walk away wondering which car actually has the smallest footprint. Here’s the twist most people miss: the cleanest choice isn’t decided at the tailpipe. It’s decided across the whole life of the car.

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Dealership labels rarely capture a car’s full life‑cycle impact.

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Are we asking the wrong question about “clean” cars?

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I spend a lot of time helping Aussie and Kiwi buyers decode those labels. A recent example: Sarah in Auckland was set on a small petrol SUV because its spec sheet looked tidy. We ran the numbers for her daily commute and the local grid. A modest BEV, charged at home on a low‑carbon tariff, cut her lifetime emissions by more than half and her running costs by a third. The data usually points the same way.

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Better questions to ask:

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How big is the battery and where was it made?
What will power my kilometres (my grid, my charging times, my tariff)?
What’s the expected lifetime mileage and how heavy is the car?

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What do those emissions numbers actually mean?

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g CO2/km or g CO2/mi: direct greenhouse‑gas measures, common on WLTP (EU/NZ/AU) and EPA (US) labels.
L/100 km (ICE) and kWh/100 km (EV): energy use on the road.
MPGe and g/mi: mostly US labels; useful if you’re importing specs.

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Handy conversions you can use in NZ or Australia:

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Petrol tailpipe CO2 ≈ 2.31 kg per litre burned. Diesel ≈ 2.68 kg per litre.\n
- Quick rule: petrol g CO2/km ≈ 23.1 × (L/100 km). So 7.0 L/100 km ≈ 162 g/km.
- Diesel g CO2/km ≈ 26.8 × (L/100 km). So 5.5 L/100 km ≈ 147 g/km.
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EV use‑phase CO2 ≈ (kWh/100 km × grid g CO2/kWh) ÷ 100.\n
- Example: 17 kWh/100 km on a 120 g/kWh NZ grid ≈ 20 g/km.
- On a 550 g/kWh grid (parts of the NEM), the same car ≈ 94 g/km.
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Standards that matter (and what they actually do)

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Euro 6 (widely mirrored in AU/NZ type approvals) clamps down on local pollutants: NOx, particulates, hydrocarbons, carbon monoxide. Later Euro 6 packages added Real Driving Emissions (RDE) to measure pollution on the road, not just in the lab. Note: Euro 6 targets smog‑forming and health‑damaging emissions, not CO2.
Euro 7 (rolling out in the EU) tightens pollutant control, adds limits for brake dust, and introduces battery durability requirements. It doesn’t apply here directly yet, but it will influence what vehicles are built and imported.
US EPA/NHTSA: labels show tailpipe CO2, smog scores and MPGe. Even if you’re not buying in the States, their format is a good model for reading across specs.

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So, how much CO2 are we really talking about?

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Here’s the short, evidence‑based picture:

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Lifecycle matters: include raw materials, manufacturing (battery cells in particular), fuel or electricity production, on‑road use, maintenance and end‑of‑life.
Battery manufacturing typically adds roughly 60-150 kg CO2e per kWh. A 60 kWh pack made with mid‑range assumptions ≈ 4.8 t CO2e up front. Cleaner factories push that down.
Despite that “backpack”, modern BEVs commonly emit 40-75% less GHG over their full life than comparable petrol cars. In grids like NZ’s, the gap is often larger; in coal‑heavy grids, smaller but still usually favourable for BEVs.
Payback time: many BEVs offset their extra manufacturing emissions within 10-40,000 km on low‑carbon grids, and typically within a few years in most markets. After that, they keep compounding the benefit.
Health angle: EVs have zero tailpipe NOx/PM, a big deal for urban air quality. Non‑exhaust particles (tyres/brakes) remain for all cars; Euro 7 starts to address this.

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What about batteries: making them, using them, recycling them?

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Battery production and recycling shape the upfront emissions profile.

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Battery production is improving fast. Factories switching to low‑carbon electricity and newer chemistries cut the CO2 per kWh. Materials matter too: LFP batteries avoid cobalt; nickel‑rich chemistries offer higher energy density. Mining brings real social and environmental risks, so it’s worth checking the maker’s sourcing and due‑diligence policies.

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End‑of‑life is shifting from problem to resource:

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Pyrometallurgy is robust and recovers nickel/cobalt/copper well, but can lose lithium.
Hydrometallurgy uses chemical leaching to recover more lithium and is now common for “black mass.”
Direct recycling aims to rejuvenate cathode materials with lower energy and is scaling up.
Expect rising recovery rates and more recycled content because policy is moving that way globally. Many brands here already offer battery take‑back; ask to see it in writing.

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What does the wrong choice feel like in real life?

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Priya in Melbourne chose a PHEV “for the best of both worlds.” Her apartment made charging awkward, so she rarely plugged in. The car ran as a petrol most days, fuel bills crept up, and the promised emissions cut never arrived. The tech wasn’t the problem-her setup was.

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Sam in Wellington went for a small BEV with a 55 kWh pack. He charges at home on a night‑saver plan, mostly from a very low‑carbon grid. His weekday drives are quiet, cheap, and clean. On holidays he books a fast‑charger stop like a coffee break. Same roads, very different outcomes-because the context fit the choice.

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How can you quickly estimate a car’s footprint before you buy?

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Use the MILE framework:

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M Manufacture: battery size × 60-100 kg CO2e/kWh gives a conservative backpack estimate.
I In‑use: for ICE, L/100 km → g/km with the 23.1 (petrol) or 26.8 (diesel) multiplier. For EV, kWh/100 km × your grid g/kWh ÷ 100.
L Location of energy: your charging mix and timing matter. Night tariffs, rooftop solar, and greener states/regions shift the numbers.
E End‑of‑life: check maker take‑back and recycling commitments; they’re becoming standard.

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What’s the smarter way to choose a lower‑impact car in Australia or New Zealand?

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\n Get your real needs straight.\n
- Weekly kms, typical trip lengths, towing, long‑weekend patterns, driveway access to power.
- If you can plug in at home or work most days, a BEV is usually the lowest‑impact choice.
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\n Run the quick maths.\n
- ICE: g/km = 23.1 × L/100 km (petrol) or 26.8 × L/100 km (diesel).
- EV: g/km = (kWh/100 km × grid g/kWh) ÷ 100.
- Example: A 7.0 L/100 km petrol hatch ≈ 162 g/km. A 17 kWh/100 km BEV in NZ at 120 g/kWh ≈ 20 g/km; in a 550 g/kWh region ≈ 94 g/km.
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\n Estimate lifecycle and payback.\n
- Battery backpack: 60 kWh × 80 kg/kWh ≈ 4.8 t CO2e.
- If your BEV saves 100 g/km vs your ICE, every 10,000 km saves 1 t CO2e. You’d “pay back” that 4.8 t in ~48,000 km. If you save 150 g/km, it’s ~32,000 km.
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\n Right‑size the battery.\n
Bigger packs add upfront CO2 and cost. Choose the smallest battery that comfortably covers your week plus one bad‑weather day, then plan charging for road trips.
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\n Check the standards and air quality angle.\n
Look for Euro 6 (or newer) compliance for any ICE you consider; it cuts NOx/PM. Zero tailpipe beats low tailpipe if you live in dense suburbs or CBDs.
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\n Plan your charging mix.\n
Home overnight on a low‑carbon or time‑of‑use tariff is gold. If you have solar, set the car to charge when the sun’s out. For apartments, ask about metered EV sockets or shared chargers.
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\n Verify recycling and durability.\n
Capacity warranty (e.g., 70% after 8 years) shows durability. Ask for battery take‑back details and any published battery carbon‑footprint data.
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\n Match the vehicle to your life, not the brochure.\n
- Urban commuters with a driveway: a small BEV is usually the sweet spot.
- Apartment dwellers: if charging is patchy, a BEV can still work if your building or workplace provides regular access; otherwise, be cautious with PHEVs unless you’ll plug in daily.
- Rural or long‑distance: consider a BEV with reliable corridor fast‑charging or, if that’s not practical yet in your area, the most efficient ICE/hybrid you can find, and revisit BEVs next cycle.
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Common worries, answered

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“What if I need to replace the battery?” Degradation in modern packs is slow, and warranties cover many years. Most packs outlast first ownership and get a second life or are recycled.
“Fast chargers are busy.” Peak times can be, so plan like you would for petrol during holiday rushes. Day‑to‑day, home charging avoids queues entirely.
“PHEVs are the best compromise.” Only if you plug in-often. If you won’t, get a very efficient hybrid or a BEV you can charge.

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Your next move

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Shortlist two or three candidates that fit your space and budget.
Pull the official energy‑use numbers and run the simple g/km and payback sums.
Check charging options where you live and drive; switch to a greener/night tariff if you can.
Ask about battery sourcing, warranty and take‑back. If a dealer can’t answer, that’s a signal.

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Home charging often makes the lifetime emissions math work in favour of EVs.

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The shift is this: stop judging cars only by the fuel sticker and start judging them by their life.

Which Car Is Really Cleaner?