How much energy does your Dell Computer use? Some use more than others. In 2007 Dell began participating in the governments Energy Star Program and now has several Optiplex models that are certified as Energy Star. How much energy your Dell computer uses depends on how long it is left on and whether you enable the energy saving settings such as shutting he monitor off after a certain period of time. For more on how much energy is used by different brands of computers see this article.