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How much electricity does a smoke alarm use?

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Thursday 22 May 2008 8.53am
After googling how much power various electrical items use,
I read that a TV on standby uses 80% of the power it would use if it was turned on.
I have a mains smoke alarm with battery back-up which has a green light on permanently and a red light that flashes every 30 seconds. Just wondering if a smoke alarm 24/7 uses more power than a TV. Does it?
Thursday 22 May 2008 9.49am
Mains powered smoke alarms are "always on" - the battery is an emergency back-up should the mains fail. Therefore, there is no "standby" mode for mains powered smoke alarms.

All the flats in Boss House have one of these mains powered smoke alarms.

The alarm draws 40mA and EDF charge me 16p per unit of electricity for the first 108 units and 10p thereafter.

So, if the only thing switched on in my flat was the alarm, it would cost 1.037 a month to run.

A television draws about 0.9 amps and, if it where running for 24 hours a day (like the alarm) and it was the only appliance switched on in my flat, it would cost about 23 a month to run.

I tried watching the alarm as a cheap substitute to the TV - have to say it's a bit boring.
Thursday 22 May 2008 2.21pm
I was only wondering because if I go into the hall at night I could read a newspaper under the green light glow from the smoke alarm. It seem unnecessarily bright.
I get electricity and gas from EDF.
My quarterly bills from 6th Feb - 9th May were:
Electricity 50-06
Gas 32-46
Very reasonable I think. Mind you I'm hardly ever home.
And nectar points for submitting reading online and Prompt Payment.
Combination boiler has halved my gas bill.
Thursday 22 May 2008 3.07pm
Ah, I see, the green glow.

That's an LED.

An average green LED with 2.5v at 20mA would cost (about) 0.0115 per month to run, given the EDF parameters in my post above - i.e. one penny.

Not going to break the bank!
Friday 23 May 2008 2.54pm
is that one pound, and three point seven pence, or one thousand and thirty seven pounds?
If it's the second one I can't quite believe it's correct - Have you done your math right?
Friday 23 May 2008 3.12pm
it's the former!
Friday 23 May 2008 3.50pm
thanks, that makes more sense.

Why don't you switch off the TV set, and go and do something less boring instead? .... like walking round outside and looking at real life - it's often a lot better than staring at the TV 24/7 ?
Wednesday 14 September 2011 1.42pm
I've got a related question - would be grateful for an answer. I have a similiar kind of mains-powered smoke alarm, in fact two or three of them. All fine, except that the one in my bedroom, over my bed, keeps me awake at night - for the reason Phoney mentions - that LED is insanely bright. Given that it's obviously a bad idea to cover the thing up, I'm pretty keen to figure out a solution so I can get a good night's kip. (And eye-masks slip off during the night, so they only work for so long.)

Can anyone advise on how to remove the LED bulb, or at least get to it and safely cover it up? (Blu-tack, perhaps.) I can't even get into the smoke alarm to find the bulb. I already know that the alarm bleeps perfectly well when it's running low on battery, so I don't need the LED bulb as a low/dead battery indicator.
Wednesday 14 September 2011 4.19pm
Try black electrical tape. Its quiet thick so probably wouldnt shine through
Friday 16 September 2011 7.42am
Thanks Pops - but wouldn't that block the passage of smoke to the alarm so that it wouldn't work?
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