Every carbon emission starts with energy. And every unit of energy, no matter how large, traces back to one tiny measurement: the joule.
Understanding joules is the key to understanding why your laptop, your phone, and the data centres storing your files all produce carbon emissions. It is simpler than you might think.
What is a joule?
A joule is the energy needed to lift a 100-gram object (like a small apple) by one metre. That is it. It is a tiny amount of energy.
To feel how small a joule is: a single heartbeat uses about 1 joule. A mosquito flying for one second uses about 1 joule. Clicking your mouse button uses about 0.001 joules. It is the smallest practical unit of energy we use in everyday measurements.
The formal definition is that 1 joule equals the work done when a force of 1 newton moves an object 1 metre. And 1 newton is roughly the force gravity exerts on a 100-gram object, hence the apple.
Why joules matter for everything
Joules unify all forms of energy into one measurement. Mechanical energy (lifting, moving things), thermal energy (heat), electrical energy (powering your laptop), and chemical energy (the food you eat) are all measured in joules.
When you eat a 2,000 kcal diet, your body processes about 8.4 million joules (8.4 MJ) of chemical energy in a day. Your body converts that energy at an average rate of about 80 watts, which means 80 joules per second. You are, in energy terms, an 80-watt machine.
From joules to watts
A watt is simply one joule per second. It measures the rate at which energy is used, not the total amount.
When your laptop charger says 65W, it means the laptop is consuming 65 joules of electrical energy every second. A desktop computer at 200W uses 200 joules per second. A phone charger at 20W uses 20 joules per second.
This is the bridge between the tiny joule and the electricity bill you pay. Energy is measured in joules. Power (the rate of energy use) is measured in watts.
From watts to kilowatt-hours
Your electricity bill is not in joules or watts. It is in kilowatt-hours (kWh). Here is the chain:
- 1 joule per second = 1 watt.
- Sustain that for one hour (3,600 seconds) and you have used 3,600 joules, which equals 1 watt-hour (Wh).
- Multiply by 1,000 and you get 1 kilowatt-hour (kWh).
So 1 kWh = 3,600,000 joules. That is 3.6 million apple-lifts worth of energy.
A practical example: if your laptop draws 65W and you use it for 8 hours, that is 65 x 8 = 520 Wh = 0.52 kWh. If your electricity costs around 0.40 EUR per kWh (typical in the Netherlands), that day of laptop use costs about 0.21 EUR in electricity.
From kWh to carbon
This is where it connects to your digital footprint. Every kWh of electricity produces a certain amount of CO2, depending on how your country generates its power. This is called carbon intensity.
In the Netherlands, 1 kWh produces roughly 284 grams of CO2. In France, it is about 85 grams. In India, it is 708 grams. Same energy, very different environmental cost.
So your 8-hour laptop session at 0.52 kWh produces about 148 grams of CO2 in the Netherlands, 44 grams in France, or 368 grams in India. The laptop does the same work. The carbon depends entirely on the grid.
Energy consumption is the largest contributor to digital carbon emissions, but it is not the only one. The manufacturing of devices and server hardware (known as embodied carbon), the water used to cool data centres, and the materials mined for components all add to the total environmental footprint. When we talk about digital carbon, energy is the piece you can most directly measure and reduce, but the full picture is broader.
The chain in one line
1 joule, used at 1 joule per second = 1 watt, sustained for 3,600 seconds (1 hour) = 3,600 joules = 1 Wh, multiplied by 1,000 = 1 kWh. Multiply by your grid's carbon intensity and you get grams of CO2.
Everything traces back to that little apple.
Why Kiran cares about joules
Kiran measures the energy your device consumes and translates it into carbon emissions using your country's grid intensity. Every file stored on your device uses energy to maintain. Every background process draws watts. Every unnecessary app adds to the load.
When Kiran removes digital waste and optimises your system, it reduces the total watts your device draws. Fewer watts, fewer joules per second, fewer kWh over time, less CO2. The savings are small per file, but they compound across millions of users and billions of files.
It all starts with one tiny unit of energy.