  Energy is today the most critical environmental challenge. The amount of
carbon emissions contributing to climate change is significantly influenced by
both the production and consumption of energy. Measuring and reducing the
energy consumption of services is a crucial step toward reducing adverse
environmental effects caused by carbon emissions. Millions of websites rely on
online advertisements to generate revenue, with most websites earning most or
all of their revenues from ads. As a result, hundreds of billions of online ads
are delivered daily to internet users to be rendered in their browsers. Both
the delivery and rendering of each ad consume energy. This study investigates
how much energy online ads use in the rendering process and offers a way for
predicting it as part of rendering the ad. To the best of the authors'
knowledge, this is the first study to calculate the energy usage of single
advertisements in the rendering process. Our research further introduces
different levels of consumption by which online ads can be classified based on
energy efficiency. This classification will allow advertisers to add energy
efficiency metrics and optimize campaigns towards consuming less possible.
