Efficency of electrical heat and light

[hollis]

We are having a disagreement about the fact I maintain that in an electrically heated home, during the winter months you may as well leave lights on if you want to because the energy from the lights will contribute to the total heat of the room the same as electrical resistive heaters. Ie, if a vessel (home/room) would need say 2000 w of elect heaters on to maintain 70 degrees. I say you would get the same amt of heat from 10- 200 watt bulbs,.or a hundred 20 watt florescent ones,.. 4-500w clothes irons or a 2000W motor. My partner says that in the case of the bulbs that the light energy is lost but I will guess that and light (or more infrared emissions) hit objects in the room, walls etc and heat it up to the same amt as anything else. I know some elderly people that live a rather dark,molelike existence by turning off most lights to "save money" in their all electric homes. Same with some people with S.A.D. that could use the extra light.
If that's the case could you not also keep some of the heat costs down by coating the inside of exterior or less heated walls with coatings that reflect radiant energy back into the room slowing down its loss to the outside? I understand that there are some new paints that are light colored but look pretty conventional that reflect a fair amt of IF radiant energy.

 

[chroot]

hollis,

Your instinct is correct -- incandescent light bulbs are actually more effective at producing heat than light. In a perfectly insulated house, a string of light bulbs would be just as effective as central heating.

In a real, imperfectly insulated house, the rate of heat transfer across the insulation depends on the temperature gradiant across the insulation. Loosely speaking, if you put all the heat in one spot (say, the ceiling above a lamp), you'll lose more of it through the insulation than you would if the same heat were distributed uniformly through the volume of the house.

- Warren

 

[Graeme Robinson]

It is a common misconception that leaving lights on in an electrically heated home will contribute to the overall heat of the room. While it is true that the energy from the lights will add some heat to the room, it is not an efficient way to heat a space.

Firstly, the amount of heat generated by light bulbs is significantly lower compared to electric resistive heaters. For example, a 200 watt light bulb will only produce a fraction of the heat output of a 2000 watt electric heater. Therefore, it would take a large number of light bulbs to match the heat output of a single heater.

Secondly, it is important to note that the heat generated by light bulbs is mostly in the form of infrared radiation, which is not as effective at heating a space compared to convection heating from an electric heater. Infrared radiation heats objects, such as walls and furniture, rather than the air in the room. This means that the heat from light bulbs may not evenly distribute throughout the room and may result in hot spots and cold spots.

Moreover, leaving lights on for extended periods of time can significantly increase your electricity bill, which may negate any potential cost savings from using them for heat. It is more cost-effective to use a dedicated electric heater for heating a room.

As for using reflective coatings on walls to reduce heat loss, this can be an effective way to improve the energy efficiency of a home. However, it should be noted that these coatings primarily work by reflecting heat from the sun or from sources inside the room, rather than from light bulbs. Therefore, while they may help to reduce overall heat loss, they would not significantly contribute to heating a room through light bulbs.

In conclusion, while it is true that light bulbs can add some heat to a room, it is not an efficient or cost-effective way to heat a space compared to using dedicated electric heaters. It is important to use heating methods that are specifically designed for heating a room, rather than relying on alternative sources such as light bulbs. Additionally, reflective coatings can be a useful tool for improving energy efficiency, but should not be relied upon as a primary source of heat in a home.