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Energy cost of 4 x 5W led downlights

Discussion in 'Electrics UK' started by Jupiter01, 12 Sep 2021.

  1. Jupiter01

    Jupiter01

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    I have various lights outside my house and they stay on for around 5 hours each night.

    Can someone please provide an approximate electricity cost for these. I was wondering if it would make much difference if I dropped this down to 3W.
     
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  3. ETAF

    ETAF

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    Simply , and very simple way to compare - although other factors may apply

    the rate you pay is based on KW for 1 hour
    KW = 1000 watts
    so 4x5W = 20W

    1000 / 20 = 50 Hours

    so you can keep those lights on for 50Hrs and pay , whatever your KW rate is somewhere between about 16p - 25p

    so if you reduce to 3W
    then 4 x 3W = 12W

    1000/12 = 83.3 Hours

    so you can keep those lights on for 83.3 Hrs and pay , whatever your KW rate is somewhere between about 16p - 25p

    5hrs each night

    50/5 = 10days

    83/5 = 16.6 days
     
    Last edited: 12 Sep 2021
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  4. Jupiter01

    Jupiter01

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    Let's be pessimistic and go with 25p per KW. That's only 25p every 10 days. I thought it may be a lot higher.
    Thanks again.
     
  5. winston1

    winston1

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    Well 3W is 60% of 5W so clearly changing will save 40% energy costs. But lights will be 40% dimmer as well. You don’t get out for nowt.
     
  6. mattylad

    mattylad

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    Just think how much those with the massive old 500w ones will be paying.. :)
     
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  7. Harry Bloomfield

    Harry Bloomfield

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    The 3w lamps will cost 3/5 as much as the 5w to run. 20w total consumption versus 12w using 3w LED's.

    I have several 3.5w LED's in use around the house, inside and we find them perfectly adequate. Hall, landing, bathroom and downstairs toilet are all adequately lit by 3.5w ceiling lights. How much actual light is needed, depends very much on the task being carried out and the type of fitting the lamp is in. Outdoors, I use 8w LED for area lighting, even that makes little difference due to the size of my garden. If I need to find my way around my garden or drive after dark, then I have a series of remote control discharge lights mounted at the eaves, controllable from my phone, via Alexa.

    The 8w I also have controlled on and off via Alexa, programmed to come on at dusk, off at 11pm.
     
    Last edited: 13 Sep 2021
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  9. winston1

    winston1

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    Redo your maths there. How can 3W cost more than 5W?
     
  10. Jupiter01

    Jupiter01

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    Is the Lumens rating significant here or is that implicit in the Wattage of a bulb?
     
  11. Harry Bloomfield

    Harry Bloomfield

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    Wattage is the input, lumens is the output. Higher lumens per watt means higher efficiency.
     
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  12. ETAF

    ETAF

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    As said lumens is the amount of light you get out , the energy turns into heat and light.
    Also the type of light , warm light, cool light , daylight makes a difference to how the area looks.
    We had a daylight and a cool light LED strip in son-inlaws garage and the difference was quite marked, changed to all daylight 6500K
    You may also see Colour Temperature Value, in Kelvins K - (same scale as Centigrade BUT the 0 starts at absolute, rather than freezing water), thats the light temp - https://www.ucl.ac.uk/slade/know/746
     
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  13. Swwils

    Swwils

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    Depending on where you live there is also effectively an ecological cost also that you may want to consider.
     
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