The British Gas EnergySmart energy meter

This box is known as the “British Gas EnergySmart” energy meter, and is available free to British Gas customers who sign up to their EnergySmart pricing plan. It’s called EnergySmart because instead of paying someone to come and read my meter, it’s now my job to crawl behind the telly every month. If I forget I get an estimated bill, which is bad.

See, that’s smart that is.

What’s even smarter is taking one of these things apart Like the nice man on the EEV Blog says – “Don’t turn it on, take it apart!”.

The whole thing consists of the remote display, a clip-on induction loop and a remote, battery powered transmitter unit. The idea is the induction loop gets clipped onto one of the fat grey wires coming out of the electricity meter, and then plugged into the remote transmitter. This little mess can then be hidden inside whatever half-arsed thing your electricity meter lives in (really, nobody seems to ever lock their meters away tidily. And why are they never in easily accessible places? “Oh no, my oven is on fire I need to turn the power off so let me just move the TV and this bookcase, it’s no bother”*).

The base unit has “GEO Minim” silkscreened onto the PCB, indicating that this is part of Green Energy Options’ Home Energy Hub system. It’s interesting that the unit retails for £39.50. They show other, more advanced models but there seems no option to buy them.

The base unit needs pairing to the transmitter, meaning more than one base unit can watch the same transmitter. Not the other way around though, that causes confusion to the little white box. Once paired up the display shows the number of kW/h being consumed in a variety of numbers and graphs. It also shows the amount of ozone layer you’re depleting, and how much money you might be currently spending. I have no idea how this works, but there is a manual.

The insides of the units are quite interesting. The base unit has bugger all inside really, just a small L-shaped board and a screen. On it are a number of small chips with the following written on them

• 25L080A1 SN0929 PU8
• SIL T630 A0LVP 0931+
• Si4322 0932AR F006
• There is also a USB port for power

A bit of Googling revealed the Si4322 chip is a

single chip, low power, multi-channel FSK receiver designed for use in applications requiring FCC or ETSI conformance for unlicensed use in the 868 and 915 MHz bands.

Inside the transmitter is space for three C cell batteries, and a rectangular circuit board containing the following chips

• VH9Ad LMV358 AM8
• SIL T634 AONHI 0934+
• Si4022 0922AR B018
• 905010WP K930Q
• There is also a sync button and four solder pads marked “PL1″

The Si4022 is a

single chip, low power, multi-channel FSK/OOK transmitter designed for use in applications requiring FCC or ETSI conformance for unlicensed use in the bands at 868 and 915 MHz.

So the communication between sensor and base unit is one-way. I think the USB port is just for power, the device doesn’t look clever enough to support any form of PC comms. It must have a very limited microprocessor (possibly what the SIL chips are) as the unit doesn’t support any form of data logging beyond “how much energy have I used today” in the form of a bar graph and the ability to set a daily energy usage target.

I’m interested if anyone can work out what the other chips are, putting their details into Google isn’t that useful.

Currently my house is using 0.70kw of electricity. I expect the “resting” consumption to be something around 0.5kw since I have my server and associated network hardware constantly running, plus a few low current items such as a PVR on standby.

The meter seems reasonably accurate. Switching my 1500W electric heater on has made the energy consumption of my home jump to 2.53kw. My wattmeter shows the electric heater is consuming approximately 1500W of energy. I’m not entirely certain where the extra 330W of electricity is going though.

* – This actually happened to me.