For years, consumers have gauged their electricity usage with the monthly bill. Coming days or weeks after the end of the period it isn't a very efficient tool if you want to cut you household usage, but a new breed of meter is changing all that and can provide real-time updates that give you an instant indication of the cost of running a house full of gadgets.
U.S. President Barack Obama has pledged to put 40 million of the so-called "smart meters" into American homes as part of the economic stimulus package but in some European homes the devices are already a reality and helping users to save month.
At the Cebit IT fair in Hanover last week, German utility Energie Baden-Württemberg (EnBW) was demonstrating its smart meter, which has been available to customers since late 2008.
The meter is available to homes for €5 per month (US$6.34) but customers who use its many reporting features can typically save more than that amount in electricity usage, said Jörn Kröpelin, from the company's strategic product department.
The meter itself has a simple LCD showing current consumption so subscribers need a PC to take advantage of its benefits.
There are two interfaces available. One Web-based interface provides reports down to 15-minute intervals via EnBW's server and includes historical data as well so users can, for example, compare current usage to that of their house the same time last month or last year or, via a recently added function, to that of an average home.
The meter reports to EnBW once every 15 minutes via your home's broadband connection and within 30 minutes that information is available online through the Web site.
A second option provides real-time data direct from the meter as long as the PC is on the same network. Through this users can instantly see energy consumption and accomplish things like analyzing the usage and the cost of running individual gadgets.
Energy usage is plotted on a graph through which its possible to isolate spikes, such as when a TV is switched on, and then calculate how much it costs to run for an hour or any desired time period. You can also plug in a usage scenario, such as 2 hours per day everyday and surprise yourself by seeing how much you'll spend annually to watch TV.
During a demo at Cebit, the meter was hooked-up to a single appliance, an espresso maker, and after making a single cup it calculated the annual running cost to be around €1.50 assuming four cups per day.
Among the users of the meter is Kröpelin himself.
"I was surprised by how much energy was used, even when I tried to switch everything off," he said. After cutting power to all the obvious appliances and switching off lights the meter was still registering energy usage -- the result of long various sensors and adapters around the home that did unseen and forgotten tasks. These added up to around 200 watts of constant energy use.
The next stage of the technology is to get the meters to communicate directly with gadgets. Initially this will likely work by plugging in appliances via adapters that can talk to the meter but could eventually work with products that have embedded intelligence.