Think that turning on the light switch translates to the same amount of carbon dioxide emissions during all hours of the day? Think again.

Last Friday saw the creation of, a United Kingdom-based website that allows UK citizens to view the varying carbon intensity of their energy usage throughout the day.
The site tracks the carbon footprint of a KW of energy over time. Demand for electricity fluctuates depending on the time of day and season of the year. Peak hours are normally daytime and early evening and cold winter months when electricity is needed for heat and the days are shorter.

When consumers use energy during these peak hours, the carbon intensity of each unit of electricity used is higher because it increases the cost of wholesale energy which causes utilities to switch on the cheapest sources, usually coal-fired power plants.

For example, on average in the United Kingdom, boiling a pot of water or running the dishwasher in the middle of the afternoon emits 40% more carbon dioxide then doing the same activities in late evening or at night.

The website “uses data from the organisations who manage the ‘balancing and settlement’ of the electricity grid to determine which power stations or wind-farms are generating electricity at any given time. It then calculates the overall carbon intensity using coefficents for each type of generation.”

The self-proclaimed goals of the tool are to “reduce carbon emissions, enable more accurate carbon accounting for businesses, promote smart-grids with smart demand, and encourage debate on energy and climate change policy.”

Duncan Clark at The Guardian’s environment blog explains its significance, “It may sound geeky but it’s hugely significant… Anyone interested in energy and emissions has known about this for years – though only on a theoretical level. For the first time, Realtime Carbon actually gives us some numbers.”

The creators of the website are hoping to reduce carbon emission and spur the creation of clean energy projects by making it easier for companies to understand, estimate, and reduce to their carbon emissions. Although a real time carbon counter was installed in New York City a month ago, there is yet to be a North American counterpart to the UK tool.

The tool cannot simply be copied because it uses energy data specific to the United Kingdom. Although the United States’ energy supply is fairly homogenous—in the sense that most regions are heavily dependent on coal and natural gas—a tool for the United States would have to be split up into states or regions because energy sources do differ significantly. For instance, Washington receives a significant supply of its energy from hydroelectric power that is virtually emission-free compared to coal power. It would be problematic to group it with Idaho or Montana, states whose energy supplies are sourced from dirtier sources.

Regardless of the difficulties involved with adapting the tool for countries other than the UK, it seems clear that this website is a landmark achievement in understanding energy supply and communicating that understanding to the public. It is a tool that, if accurate and user-friendly, could revolutionize how businesses use and think about their energy.