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Cheap centralized home power management? Answered

I would like to manage power use in my house. I would like a system where I have a computer from which I can see the power usage statistics of all outlets in the house, and can turn them off from the computer.

What is the best (cheapest) way to implement the hardware side of this? Also, is there an easy way to do this with lights in the house, that are not on outlets?



I don't know of any cheap way to monitor actual power usage. A less-than-horribly-expensive way to monitor when switches are turned on and off, and to turn them on and off remotely, is to install switching modules which speak X10 or one of the other home automation protocols. (X10, a carrier-current signalling system, is the oldest and most common, but there are now radio-based versions as well). Expect to spend at least $20 per outlet and/or wall switch for the low-end toys (made by the company which created the X10 protocol), that let you control power remotely, twice that for higher-quality hardware which also sends a signal when a human has switched it locally. Add another $100 for a basic PC interface. You *can* spend considerably more. No, that isn't "cheap". But it's the cheapest answer I know of that accomplishes what you've requested. A websearch for "home automation" will find a number of suppliers of this sort of equipment. WARNING: NEVER PUT FLUORESCENT LAMPS ON A DIMMER UNLESS THEY ARE SPECIFICALLY CERTIFIED AS DIMMABLE -- EVEN IF YOU NEVER INTEND TO DIM THEM. Failing to obey this rule can create a fire hazard. If you want to switch fluorescents, get a module which is based on a relay rather than a triac. (Can you tell I've been considering doing this with my own place? I actually have a batch of X10-made modules that I picked up for experimentation some years ago, but they're mostly triac-based and I've been moving to CFLs.)

Thanks for the info! I'm quite disappointed that this technology is so prohibitive.

However, if anyone else (with a bigger budget) is interested in this idea, they may want to look at the PowerBox. It uses a relay to turn the power on/off, as well as measuring usage, and is controlled via a serial port. It's about $45, but most of it came from Digi-Key. Because of Digi-Key's price scaling, it looks like it would be about $40 each if you plan on building 10-100 units. This is significantly cheaper than a ``Watts up?'' that offers similar features (about $100)

The PowerBox uses a mega32 to create the signal; I know that it is fairly easy to get this thing using either serial or USB. From there you have a number of options, it seems to me that the cheapest would be Bluetooth (class 1 has a range of 100meters). USB is very easy (read:cheap) to do over Bluetooth (because much of the Bluetooth stack was based off USB), and SparkFun carries a tiny class 1 Blutooth/USB part for about $10. That's about $50 per outlet, and no cost for the PC interface (if you already have Bluetooth). While still pretty expensive, this is way better than a lot of the other options, considering the features.

Also be careful with any other similar inductive loads: computer power supplies, newer gadget switch mode power supplies, phone chargers, anything with a motor, most things with any form of transformer...Relay still has its place in the electricity world :D there's a lot to be said for good-ol' copper conductors!