It looks like a traffic light, sitting there in a cupboard or under the stairs. When your home is using minimal electricity, the green light shows. Orange means you've stepped up your power usage, and the red light comes on when you switch on a device that gobbles up electricity: the oven or the tumble drier.
This power consumption signaller is the main manifestation of the so called "Intelligent Grid" at the moment, also known as the "Smart Grid".
In Britain and other parts of Europe, you can find these smart meters in just a few homes of early adopters, people with an eye on global warming who also want a little more control over the power they use as and when they are actually using it, rather than waiting for the next bill to arrive.
A nice talking point when friends drop round.
But it is a talking point that we may all have to get used to talking about soon. The Smart Grid is something that high technology people are getting very excited about. Some even call it the dawn of a new sort of economy. It is similar to the coming of the Internet, but bigger, much bigger.
It is certainly going to cost billions to install 48-million new smart electricity meters in every consumer's home and office in Britain by the official government target date of 2020. Some experts think it may be moved forward to 2016.
The 2020 date is significant because that's the date by which the European Union has signed up member countries to reduce carbon dioxide emissions by 20 percent from 1990 levels.
If cutting greenhouse gasses is the aim, then the smart meter programme is the thin end of what may turn out to be a thick and expensive wedge.
Simple awareness that consumers are using electricity is - I suggest - unlikely to do much to cut consumption of electricity made from burning carbon.
There will have to be carrots and sticks in the form of significant price differentials. The Smart Grid will provide the intelligence to deliver them. Electricity supply companies must already be working on deep studies of users' behaviour: what incentives will people need to switch to "cheap" off peak power to do routine things.
Will the coming of smart meters lead to a string of home appliances that can be switched on remotely (perhaps by the power company) when surplus electricity is available in the system. Your tumble drier communicating direct with the power company, and responding to it ... to keep your electricity bill down. Creepy!
Some visionaries go much further than this. For them, the switching power made possible by the networking together of smart meters will eventually usher in the day when most premises are power producers as well as power consumers.
Domestic windmills, solar panels and even hydrogen cells in homes and offices may generate power that can be monitored in and out of the grid by local smart meters.
Just as mainframe computers gave way to the desktop and laptop machines and localised computer power, so the smart meter system may one day make possible localised power supplies, moderated by the information flows generated by those smart meters under the stairs.
That anyway is what the enthusiasts say. It seems to me that it's a lot further off than 2020. Those 48-million smart meters are just the start (perhaps) of something big.
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