Smoke Detector Running Costs

pejayuk

Hi, I wasn't sure which board to post this on, but anyway. I just got myself a free energy monitor from British Gas. I was surprised that with everything in the house switched off, I was still using about 60-70 Watts!

I have now discovered that the smoke detectors are using the power. I have 2 of the mains powered type made by Ei. They are linked together wirelessly so that if one is triggered, they both sound.

Now I appreciate these are life savers, but it still seems pretty uneconomical. I have worked out they will cost over £90/year to run.

They were only installed a few months ago and I can't change them because the property is rented.

Just wondered if anyone else had encountered a similar thing or know if this is normal?

Thanks for reading this.

pejayuk

moonrakerz

The detectors are not using the power. It is just the gross inaccuracy of these stupid monitors!

The only accurate way to monitor power consumption is to watch your mains meter wheel or flashing light - but you might have a long wait there

pejayuk

Thanks for the reply. You were right, the monitor is not accurate. In just two days there was over 2KW higher usage shown on the monitor than the actual meter readings I took.

I'm just glad it was free and I didn't pay the £39.99 British Gas say they are worth! I guess they are ok if you just want a rough idea, but that's about it.

chris1973

I noticed the same with a Low Energy Bulb, anything below a certain wattage (about 35W with mine) shows as a grossly inaccurate reading. A phone charger showed a usage of 41W, whilst the same charger measured 2.3W with a £600 electronics multimeter - far more representative of its real life consumption.

These things are banded about like the Adult version of Santa Claus, but there is no way that something mass produced for about £5 in China can have precision accuracy and close tolerance calibration and components to give the stalwart accuracy which some here place in them. I surprised they haven't got 'Sold for Novelty Value only' stickers on them.

Every household already has a precision measuring instrument in place to monitor energy usage, its an Electricity Meter, and you can easily check your household usage by taking a daily reading and multiplying the number of units used by the KW/H price shown on your bill or the website site of the energy provider you are with - it really does take less time than an average tv commercial break to do, and will save you a good chunk of what your monthly DD Electricity payment would be, by not needing / buying one of the energy monitors!.

If you want to know what an individual appliance consumes, read the rating plate label which is stuck on it.

If you think about it, a battery powered smoke detector will run for over a year on a standard 9v battery or 10 years with a Lithium battery!, therefore its fairly safe to assume that its current requirement is very very low. The Mains ones really aren't that different in design, and I suspect the biggest consumption will be the losses in the built in power supply unit to drop the mains voltage to a low voltage for the internal components.

At a guess I would say consumption would be under 2 Watts per detector, maybe even closer to 1W.

Kilty_2

It wouldn't surprise me that these monitors are inaccurate at very low power consumption - the working range of the CT sensor that's used is probably an issue