The annual energy used to transmit, process and filter spam totals 33 billion kilowatt-hours (kWh), or 33 terawatt hours (TWh), the equivalent to the electricity used in 2.4 million homes, reads a report put together by the ICF and sposored by McAfee.

The study also adds that the figures above provide the same GHG emissions as 3.1 million passenger cars using 2 billion gallons of gasoline.

It might sound scary and impressive, but the report does feature several holes and question marks. For instance, it fails to tell just how did the researchers come up with these figures. Also, the figures themselves don’t say too much if not compared to figures provided by computers not used to fight spam.

At this point, the only reasonable conclusion is pointed by McAfee itself:

“Stopping spam at its source, as well investing in state-of-the-art spam filtering technology, will save time and money, and will pay dividends to the planet by reducing carbon emissions as well individuals,” says Jeff Green, senior vice president of product development and McAfee Avert Labs.

In other words, we’re trying to scare you or make you feel guilty, so you would buy our  software. Spam is bad, no doubts about it, but shady PR practices are bad as well.