Reducing the web's carbon footprint: Does improved electrical efficiency reduce webserver electricity use?

Webservers are major consumers of electricity and, therefore, offer important opportunities for energy conservation. Server electrical efficiency has increased dramatically in recent years, suggesting that technological innovation can curtail electricity consumption. However, over a century ago, Jevons noted reasons to expect that technologies that increase the efficiency of resource use, paradoxically, can increase consumption of those resources. Here, we investigate the extent to which recent gains in server efficiency have translated into lower electricity use. We use the Standard Performance Evaluation Corporation's dataset on the electrical consumption and efficiency of over 600 server models tested between 2007 and 2019 to identify the extent to which improvements in electrical efficiency reduce server electricity use (watts) or increase server performance (operations per second). Our analysis estimates that server design innovation tends to favor the latter over the former. Electricity reductions typically equal one-quarter to one-third of a given improvement in electrical efficiency, suggesting a conservation-offsetting rebound but not one large enough to constitute a Jevons paradox in which efficiency actually increases resource use.