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Author Topic: Is it wasteful to leave the lights on if you heat with electricity?  (Read 8695 times)

Offline Karsten

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Is it wasteful to leave the lights on if (and while) you heat with electricity? I mean, the heat of the lights is used to heat the house and as a result the eletric heaters have to heat less. Does it even out? Which kind of light bulb is the more efficient heater: CFL or incandescent? Is it more wasteful to leave CFLs burning or incandescent lights?


 

Offline Chemistry4me

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I would think that the room would have to be very very small for the lighbulb to have any effect on the temperature of the room. Even then, you might still need a 100W+ bulb.
 

lyner

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If it makes no difference to the warmth in the room, under those conditions, it will make no difference to your electricity bill either. A kWh is a kWh.
 

paul.fr

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It's only wasteful, and costing you money,if you are not using the room in which the lights are left on.
 

Offline Karsten

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It's only wasteful, and costing you money,if you are not using the room in which the lights are left on.

Why is it more wasteful if I am not in the room? I understand that turning down the thermostat is money- and eco-wise if you are not in the room, but if the room heat is regulated by a thermostat the amount of electricity used (by the heater or by the light bulbs) is not dependent on my presence, is it not? Could you elaborate please?

 

Offline Chemistry4me

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I think Paul means eco-wise if you are not in the room :)
 

Offline chrisn

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It's only wasteful, and costing you money,if you are not using the room in which the lights are left on.

Why is it more wasteful if I am not in the room? I understand that turning down the thermostat is money- and eco-wise if you are not in the room, but if the room heat is regulated by a thermostat the amount of electricity used (by the heater or by the light bulbs) is not dependent on my presence, is it not? Could you elaborate please?

It wastes energy by generating light, when you want to have heat. If you're not there to observe the light, that's a waste.
 

lyner

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It wastes energy by generating light, when you want to have heat. If you're not there to observe the light, that's a waste.
And what do you think happens to the energy when the 'unwanted' light hits a surface?
How could you be aware that the resulting heat came from the central heating or the light bulb?
If you want to reduce costs in the Summer, turn lights off when you're not n a room. In Winter it can't really make much difference because you  want to heat the house, anyway.
This hasn't really been thought out by the Environmentalists / Politicians.
 

Offline Pumblechook

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Just been reading about this on the BBC Radio 4 talkboard.

The saving from changing to CFLs is far greater than from any possible saving on you heating bill by keep old fashioned bulbs.

You might say over ten quid a year for each 60 Watt bulb replaced. 
 

Offline Karsten

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There are a lot of things that are not thought out well by environmentalists and politicians. It is unfortunate that anyone who cares about anything related to nature or the environment (for whatever reason) calls him/herself environmentalist. And some of them even work against each other. I would like to see a differentiation. Sub groups. Romantic environmentalism. Spiritual environmentalism. Profitable environmentalism. Science-based environmentalism. Being "green" is very popular right now.

From a scientific, rational point of view it seems that leaving any electricity consuming device on while heating the house with electricity makes no difference. As long as the energy stays in the house it heats the house. Does not really matter which device heats your home, and ultimately it results in heat.

Obviously (or not so obviously for many) it makes a lot of sense to reduce the heat when you are not there, when you are sleeping, or when you can just put on more clothes. I am a big proponent of the hot water bottle as well. It also makes great sense to turn of the lights when you do NOT want to heat your house. It makes a huge amount of sense to use CFLs rather than incandescent lights when you are using air-conditioning at the same time. Although there are VERY few situations when AC is necessary. Most of the time a fan or change of clothes or activity will do.
 

Offline Karsten

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The saving from changing to CFLs is far greater than from any possible saving on you heating bill by keep old fashioned bulbs.

You might say over ten quid a year for each 60 Watt bulb replaced. 

Yeah, but not if and while you heat with electricity (which you need to look at very closely because it can be eco-wise depending on how it is made). And I wish they would talk more about the real energy hogs, e.g. electric clothes dryer. While CFLs make a small dent in your electricity bill, not using the dryer makes a significant dent.
« Last Edit: 17/01/2009 19:25:27 by Karsten »
 

lyner

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The saving from changing to CFLs is far greater than from any possible saving on you heating bill by keep old fashioned bulbs.
I don't quite understand what you're saying pumblechook but the energy costs for all sources are similar, although not the same so any heat input will be the same from whatever source (light bulb or heater).
The very last thing one should do is to take out a working filament bulb and throw it away, to replace with a cfl. You should wait until it dies naturally. The energy to produce a bulb is not inconsiderable.

The £60 you quote would only be relevant if you used the bulb when you didn't need any heating. Else you could only consider the differential cost of the electrical vs the gas (or whatever) input.
 

Offline techmind

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If you're heating a room electrically with a thermostatically controlled heater, then to a first approximation, swapping to "low energy" bulbs shouldn't make any net difference to your electricity use. Of course in practice the lights might put the heat in a slightly different place in the room compared to the heating appliance (and to it's thermostat) although convection usually does a good job of mixing things up anyway.

When using gas central heating then although the consumed-energy difference should cancel out as above, owing to the inefficiencies of thermal (fossil-fuel powered) electricity generation, you do better (in terms of original fuel use, and CO2 emissions) to get your heat from the gas rather than from electricity - so CFLs would be "better". Obviously if we ever reach the day when the majority of our electricity comes from renewable sources then that would reverse.

That said, the energy use of domestic lighting, while something like 15% of electricity use, still only amounts to around 1% of national CO2 emissions, so all this legislation and fuss is still basically just fiddling while Rome burns.
Anyone would save as much CO2 by driving a car a dozen less miles per week as they would changing the bulbs in their house to ghastly low-energy ones (Yep, I don't like 'em!).

Turning thermostats down by a degree or so, or just heating fewer rooms or for fewer hours per day would save far more CO2 than swapping a few bulbs.
 

Offline Karsten

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That said, the energy use of domestic lighting, while something like 15% of electricity use, still only amounts to around 1% of national CO2 emissions, so all this legislation and fuss is still basically just fiddling while Rome burns.
Anyone would save as much CO2 by driving a car a dozen less miles per week as they would changing the bulbs in their house to ghastly low-energy ones (Yep, I don't like 'em!).

Turning thermostats down by a degree or so, or just heating fewer rooms or for fewer hours per day would save far more CO2 than swapping a few bulbs.

Completely agreed. There are many appliances that use a huge amount of energy more than the lights. Using less hot water and hang drying your clothes has a much bigger impact on your CO2 output.
 

lyner

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And, when you get a 'HIP' to sell your house, they write down, on the Energy Report, whether you are using low energy bulbs - that's supposed to be highly relevant!
 

Offline Karsten

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It may superficially show the attitude of the owner, but it says little about actual energy efficiency of the home. Like recycling everything, CFLs are what people believe will save humanity.
 

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