Overall energy usage in houses may be on the decline as more and more consumers go green, but small energy "vampires" continue to needlessly suck up power, energy experts say.

According to the Ministry of Natural Resources, 13 million homes and 380,000 buildings across Canada are responsible for producing almost 30 per cent of the country's greenhouse gas emissions.

By July 20, all desktop and laptop computers, workstations, servers and gaming consoles will have to meet new requirements in order to qualify for the Energy Star seal. Among other requirements, PC monitors must revert to sleep mode within 15 minutes of inactivity, while the entire computer must switch to sleep mode within half an hour of being idle.

But Ken Klassen, an efficiency expert, says consumers should still be mindful of precisely how much power electronic gadgets like printers and microwaves consume while in standby mode.

"In Canada overall energy usage in houses is down about 12 per cent since 1990, which is really good, but the gains would have been even more if we hadn't had all these small miscellaneous energy vampires in our houses," he said.

"There have been studies that have suggested that at leastfive to 10 per cent of all electricity that's used in the houses is due to all of these little phantom loads, these standby losses," Klassen said.

Anne Wilkins, manager of Natural Resources Canada's Energy Star program, says she'd like to see mandatory standby power guidelines in Canada. Governments in Australia, Japan and the state of California have set standby power limits.

Consumers seeking to scale back energy use can unplug their appliances when not in use, the Ministry of Natural Resources says. When shopping for new appliances or equipment, people should also check for an Energy Star seal, a designation given to energy-efficient appliances.