A DIY Home Energy Monitor Done Right

Ever wondered how many kilowatt-hours (kWhs) of electricity you were using around the home each day? You could pay $100 for a whole-house energy meter, or about $15 for a monitor that calculates usage one appliance at a time. Or you could do what one enterprising (and totally tech savvy) individual did on the cheap to measure residential power usage.

Said individual already had a meter, installed by the utility company, which featured an LED blinking a specified number of times for each kWh consumed. The trick was to track the pulses, or blinks, in a graphical fashion. Problem solved by mounting a photoresistor and a ATtiny2313, a miniscule 8-bit processor with 2 kilobytes (K) of memory and 15 lines of data, or I.O., affixed to the LED with a reusable, pressure sensitive adhesive.


image via Janne Mäntyharju

Fortunately, the highly light-sensitive LED in his meter is shielded from ambient light by a purpose-built cabinet. This created an ideal lighting situation for recording the blinks, though the utility room was too distant to run cables. Instead, the LED communicates to the server via a wireless modem, and records electricity used in an SQL database, which constructs a graphic representation on a low-power, single board computer called a Beagleboard and displays it on a digital picture frame. The frame can also display weather, calendar events, IRC chat strings (think back-door computer messaging) and security camera images – quite a load for a single motherboard!

Construction is probably less complicated than it sounds. Or maybe not. If you are, like me, of the tribe of Lud and have more bucks than savvy, you can always buy a smart meter. Still, the idea of this DIY project for home energy monitoring speaks to the volumes some are willing to go to get a better handle on their personal energy consumption.