Household lights and saving energy

[Steel Icarus]

We've just had electric smart meters fitted and a clever screen now tells us current cost per hour and how much wattage we're using at any one time. Astonishing how much of an increase the kettle or toaster causes.

What I'm unsure of though is energy saving related to lights. We've sort of instigated a habit of turning lights off when they're not needed. My question is this: is it better to leave a light on for a bit or turn it off every chance you get? I've already had a couple of people cite "my electrician mate" as saying it takes more energy to turn a light on than leave it on, and also the money saved is so negligible it's not worth bothering with.

Insider knowledge required. So tagging danski as I know he knows his stuff, but opinions informed or otherwise welcome

 

[Storm Fox]

It's only fluorescent lights that have any advantage to be been left on, then it is only a few minutes,
Old-fashioned incandescent and LEDs lights turn them off and on as needed.

The biggest saving is to swap everything for LEDs if you can. I had four mini-kitchen spotlights GU10 bulbs that were using 200W between them. Swapping them for LEDs dropped it to 24W.

 

[danski]

Wot they said ^^

 

[cupid_stunt]

I recently had smart meters fitted, and I was shocked that my use in the morning is 6p per hour*, with the a living room light on, plus freesat box/TV/sound system & laptop, when the fridge/freezer fires up that increases to 10p for a few minutes, but switching on the kitchen lights adds a whopping 3p to the total.

I've got LED lights everywhere, except the kitchen, which like Storm Fox has four mini-kitchen spotlights, although I only have two working bulbs in, otherwise I would need to wear sun glasses in there! There was a box of spares when I moved in, so I've carried on using them, but replacement LED ones are now on my shopping list.

ETA - * Once I've watched the news, the freesat box/TV/sound system goes on standby, so it's Alexa for the radio plus laptop & living room light, and I am using just 2p an hour, so to see that jump to 5p with 2 little spotlights in the kitchen is proper mad!

 

[Steel Icarus]

That's very helpful, thank you everyone.
So how long is it worth keeping a striplight on for? For example when I do laundry on Sundays it's about 90 minutes between loads. Is it better to leave the light on in the garage or turn it off during drying and on for the two minutes it takes to swap loads?

 

[Storm Fox]

That's very helpful, thank you everyone.
So how long is it worth keeping a striplight on for? For example when I do laundry on Sundays it's about 90 minutes between loads. Is it better to leave the light on in the garage or turn it off during drying and on for the two minutes it takes to swap loads?

Turn it off, I can't find it now but the energy used to turn it on is only about 2 or 3 minutes use, maybe less.

 

[platinumsage]

You also have to factor in the wear & tear on the circuitry etc and the cost of new bulbs. Sit down with a cup of tea and think about it, although that cup of tea will probably wipe out any potential savings for the next few years.

 

[Storm Fox]

You also have to factor in the wear & tear on the circuitry etc and the cost of new bulbs. Sit down with a cup of tea and think about it, although that cup of tea will probably wipe out any potential savings for the next few years.

For LED bulbs it's the heat and runtime that limits their life not turning them on and off.

Do LED Light Bulbs Really Last 10 Years?

LED bulbs are bit a more expensive than other types of light bulbs, but they claim to last a lot longer.

www.howtogeek.com

When to Turn Off Your Lights

The cost effectiveness of when to turn off lights depends on the type of lights and the price of electricity.

www.energy.gov

Do you have a source for your wear and tear claim? or you just think it does?

 

[Steel Icarus]

You also have to factor in the wear & tear on the circuitry etc and the cost of new bulbs. Sit down with a cup of tea and think about it, although that cup of tea will probably wipe out any potential savings for the next few years.

Yeah, when Mrs SI showed me the fancy monitoring screen my first question was "how much does THAT cost to run?"

 

[two sheds]

I recently bought a new 23" monitor and it said the consumption is 13 W which I don't really understand was rated as F (I think used to be A+ in old money)

 

[danski]

I recently bought a new 23" monitor and it said the consumption is 13 W which I don't really understand was rated as F (I think used to be A+ in old money)

I believe it’s an efficiency rating. Even though 13w is low consumption, it may be relatively inefficient. I think.

 

[platinumsage]

For LED bulbs it's the heat and runtime that limits their life not turning them on and off.

Do LED Light Bulbs Really Last 10 Years?

LED bulbs are bit a more expensive than other types of light bulbs, but they claim to last a lot longer.

www.howtogeek.com

When to Turn Off Your Lights

The cost effectiveness of when to turn off lights depends on the type of lights and the price of electricity.

www.energy.gov

Do you have a source for your wear and tear claim? or you just think it does?

It depends whether the bulb has sufficiently sophisticated circuitry or not:

https://www.mouser.com/pdfdocs/lumiled-avoiding-current-spikes.pdf

 

[danski]

I believe it’s an efficiency rating. Even though 13w is low consumption, it may be relatively inefficient. I think.

Well, that was my thinking when I was looking for a specific wattage GU10 led lamp (bulb). There were several of the same wattage but different energy ratings.
Now, looking at the below, I wonder if some were older and were rated before the ratings changed?

New Energy Ratings For Appliances 2024 (Latest Update)

New Energy Ratings For Appliances 2021 Energy efficiency is becoming more and more relevant in today’s society and is an important factor for consumers when it comes to the consideration around purchasing new appliances. Energy labels haven’t always been the clearest. The ever so common A+, A++...

hernebaydomestics.co.uk

 

[two sheds]

I believe it’s an efficiency rating. Even though 13w is low consumption, it may be relatively inefficient. I think.

Yes - seems to be a strange definition of efficiency they're using though. My older monitors are 30 W +.

 

[moochedit]

Yeah, when Mrs SI showed me the fancy monitoring screen my first question was "how much does THAT cost to run?"

Switch everything off except smart meter

I doubt it would use very much though.

It's things that create heat like cookers, toasters, hair dryers, kettles etc (or cold like your fridge and freezer) that use the most.

 

[A380]

I think this idea comes from the days of incandescent bulbs where it was the temperature change (leading to expansion and contraction) of the element that caused most of the ageing of the bulb* . The argument was how many minutes of electricity was 'worth' one cycle. This isn't an issue with LED bulbs in anywhere like the same way.


(*Round the world there are several bulbs that have apparently been on for decades without burning out. They all are never, or hardly ever switched off.)

 

[Winot]

Switch everything off except smart meter

I doubt it would use very much though.

It's things that create heat like cookers, toasters, hair dryers, kettles etc (or cold like your fridge and freezer) that use the most.

Yes this. Lights aren’t a major issue.

 

[MickiQ]

I had a purge something like 15 years ago where I got rid of all my incandescent light bulbs and replaced them with low energy bulbs and we have never had a bulb failure. Light fittings have been changed due to the rooms being redecorated but that is the only time bulbs get changed if the old bulb doesn't go in the new fitting.

 

[Steel Icarus]

Switch everything off except smart meter

I doubt it would use very much though.

It's things that create heat like cookers, toasters, hair dryers, kettles etc (or cold like your fridge and freezer) that use the most.

Yeah, I was being facetious

 

[Crispy]

Warning: Don't replace GU10 spots on a dimming circuit with cheap "dimming compatible" LEDs off Amazon. One of them literally exploded in a burst of literally red-hot metal shards. So I bought replacements with a recognisable brand name and replaced the dimmer with an on-off switch. This was quite a few years ago, so things are probably better now mind.

All non-bed/bathrooms in my house have this type of light, so the only downside of going to LEDs is visual. Every manufacturer's lamp looks different and even if rated at the same colour temperature will still have subtly different light. Doesn't bother me. I even have mixed warm/cool in the hall

 

[two sheds]

I've remarked before that it's worth getting good LEDs. I've not really bought any for ages so quality may have changed, but quite a few of the early ones I bought failed. I did some work for Philips and they were stressing the reliability of theirs, that they don't fail. None of their ones I've put in have failed and some are a good 5 years old.

 

[kalmatthew]

Well, that was my thinking when I was looking for a specific wattage GU10 led lamp (bulb). There were several of the same wattage but different energy ratings.
Now, looking at the below, I wonder if some were older and were rated before the ratings changed?

New Energy Ratings For Appliances 2024 (Latest Update)

New Energy Ratings For Appliances 2021 Energy efficiency is becoming more and more relevant in today’s society and is an important factor for consumers when it comes to the consideration around purchasing new appliances. Energy labels haven’t always been the clearest. The ever so common A+, A++...

hernebaydomestics.co.uk

Part of this is becuase we use tungsten equivalent Watts for perceived brightness (output) rather than something sensible like lumen, we also use Watts (sensibly) for input. Thr ratio between the two will have a massive impact on efficiency.

 

[RubyToogood]

Yes - seems to be a strange definition of efficiency they're using though. My older monitors are 30 W +.

When I was buying a new fridge, I came to the conclusion that the energy efficiency stats were just favouring bigger fridges, even though they consumed more electricity. I stopped looking at them and just looked at the energy consumption stats instead.

Presumably it's either a quirk of how efficiency is calculated (eg consumption per unit of volume) or that larger fridges are inherently better insulated or something.

 

[Chz]

I don't think it was even a few minutes for the old fluorescent bars. You were meant to leave them on because power cycles are "stressful" and energy was cheap. The actual energy use balanced out in under a minute. People just used it to justify leaving the lights on for no good reason.

Sort of like the people who disable stop/start on their cars. "Oh, it takes fuel to turn it back on". Meanwhile there are several experiments you can look up that say turning the engine on uses 7-8 seconds worth of fuel at idle, and any time you idle longer than 8 seconds you should turn off.

 

[teuchter]

rated at the same colour temperature will still have subtly different light. Doesn't bother me. I even have mixed warm/cool in the hall

This is one of the most upsetting things I've read on urban in some time.

 

[MrCurry]

This isn’t in any way an answer to the OP’s specific question, but just to point out not all LED bulbs are equal when it comes to energy efficiency and if you’ve had yours for more than a few years it could be worth replacing with newer ones.

The latest Solhetta bulbs from ikea are using just 3.4W for 470 lumens and the same brightness ones I bought just a few years ago were over 5W. £2.50 a pair isn’t going to break the bank either. The smaller E14 size 250 lumen bulbs are down to 1.8W now, which makes a windowsill lamp pretty economical.

If you have a light which is left on for hours, like a porch light, the payback period on a replacement now the price of power is so high could be pretty short.

 

[teuchter]

This isn’t in any way an answer to the OP’s specific question, but just to point out not all LED bulbs are equal when it comes to energy efficiency and if you’ve had yours for more than a few years it could be worth replacing with newer ones.

For this reason I think things have changed a bit comparing flourescent battens (not CFLs) and LED alternatives.

When I looked at it 5-10 years ago, it seemed that eg. T5 battens were actually more efficient than LED replacements, but now they seem to be pretty similar.