CarbonWatch
Below the global total, a section converts the result into familiar things: phone charges, kilometres, a tree. Here is where each of those figures comes from, and what it is really worth.
Energy
What a device draws to do its job once. These values are stable: they can be measured at the socket.
| Reference | Value used | Where it comes from |
|---|---|---|
| Smartphone battery | 12 Wh | Smartphone battery capacity: 3,000 mAh at 3.85 V, or 11.6 Wh, rounded to 12. Recent large models reach 15 or even 19 Wh — the number of charges shown is therefore an upper bound. |
| LED bulb | 10 W | Rating of an LED bulb replacing a 60 W incandescent. The market runs from 7 to 12 W depending on efficiency; 10 is the round value in the middle. |
| Kettle | 100 Wh | From physics, not from a database: raising one litre of water from 15 to 100 °C takes 4.186 kJ per kilogram per degree, or 356 kJ — 99 Wh. A real kettle loses a little to steam and to heating its own body; 100 Wh is the theoretical figure, rounded. |
| Washing machine | 700 Wh | A common 40 °C cycle on a recent washing machine. The European energy label quotes 500 to 600 Wh instead, but for the eco programme — longer and cooler than what people actually run. |
Carbon
What travelling emits, per kilometre. These are averages, and some are wide: how full a vehicle is changes its per-passenger figure more surely than what powers it.
| Reference | Value used | Where it comes from |
|---|---|---|
| High-speed trainFrance, nuclear electricity | 2 g/km | High-speed train in France, per passenger-kilometre. The figure owes more to the electricity than to the train: the French grid runs at about 50 g/kWh, and that is what puts rail two orders of magnitude below the road. The same train in Poland would not give this number. |
| City busdiesel, average occupancy | 100 g/km | Diesel city bus at the average occupancy observed over a day. Per passenger, it is the number of passengers that decides: an empty bus at five in the morning emits as much as a full one, and its per-passenger figure runs to infinity. |
| Petrol city cartailpipe | 120 g/km | Petrol city car, tailpipe emissions under WLTP homologation. This is a per-vehicle figure: with two people aboard, halve it. Same constant as the application uses, so that the desktop and the page do not tell two stories. |
| Long-haul planelong-haul, economy | 170 g/km | Long-haul, economy class, per passenger. Published references range from 100 to 250 g/passenger-km depending on the length of the flight and on whether the radiative forcing of contrails is counted, which roughly doubles the effect. 170 sits in the middle of that range, and the range is the real information. |
| Petrol SUVfamily size | 190 g/km | Family-size petrol SUV, WLTP, per vehicle. The 60% gap with the city car comes not from the engine but from mass and frontal area. |
| Cruise ship3,000-passenger ship at 70% occupancy | 250 g/km | A 3,000-passenger cruise ship at 70% occupancy, per passenger. Published estimates range from 250 to 900 g/passenger-km: the ship heats, cools, lights, feeds and runs a swimming pool as well as moving, and occupancy changes everything. 250 is the low end — the equivalence shown is therefore a cautious one. |
| Sports carnaturally aspirated V8 | 350 g/km | Sports car with a naturally aspirated V8, WLTP, per vehicle. It is here for the gap: three times the city car, a hundred and seventy-five times the high-speed train. |
| Temperate tree | 25 kg/yr | Absorption by a mature temperate tree, the usual order of magnitude of 20 to 30 kg of CO₂ a year. It varies threefold with species, age and soil, and it holds only while the tree is standing: this is a scale, not an offset. |
What these figures are not
They enter no calculation. Removing the whole section would not change the page by a single gram: the estimate is made in watt-hours and grams of CO₂e, and these references only help read them.
Two units live side by side, deliberately. Collective transport is counted per passenger and per kilometre — a half-empty train emits twice as much per passenger. Cars are counted per vehicle: with two people aboard, halve it.
The scope is the same as the rest of the site: the energy of use, and nothing else. Not the manufacturing of the vehicle, nor of the infrastructure, nor end of life. Carbon values are location-based — the real grid mix of the area, not the certificates of origin bought by the operator.
Transport factors follow the orders of magnitude of the French ADEME's Base Empreinte and of the UK government's published conversion factors; appliance figures come from energy labels, and the kettle from physics. None is carried to the decimal: they are reading aids, rounded so that the order of magnitude sticks rather than the number.