# Heater works better with lights on?

**URL:** <https://boards.straightdope.com/t/heater-works-better-with-lights-on/26227>\
**Category:** Factual Questions\
**Created:** [July 20, 2000, 12:33pm UTC](https://boards.straightdope.com/t/heater-works-better-with-lights-on/26227 "2000-07-20T12:33:21Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![MadHatter](https://avatars.discourse-cdn.com/v4/letter/m/f6c823/32.png) [@MadHatter](https://boards.straightdope.com/u/MadHatter)\
**Post date:** [July 20, 2000, 12:33pm UTC](https://boards.straightdope.com/t/heater-works-better-with-lights-on/26227/1 "2000-07-20T12:33:21Z")

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Let me take you through my daily morning winter ritual.

I get up out of bed, and switch on my portable heater. I close the door but leave my light switched on. I go to the bathroom, shower, return 10 minutes later to a nice warm room.

**However**

On some occasions I forget to leave my light switch on and when I return from my shower, my room has hardly warmed up at all. What is the reason for this? How can an “on” lightswitch make my room much warmer?

(Note, my curtains are shut, hardly any sunlight gets in.)Any ideas?

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**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\
**Post date:** [July 20, 2000, 12:39pm UTC](https://boards.straightdope.com/t/heater-works-better-with-lights-on/26227/2 "2000-07-20T12:39:24Z")

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If your bathroom is wired like mine, the lightswitch turns the outlet on and off. With the lights off, the heater wouldn’t work. Is yours giving off heat?

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**Author:** ![MadHatter](https://avatars.discourse-cdn.com/v4/letter/m/f6c823/32.png) [@MadHatter](https://boards.straightdope.com/u/MadHatter)\
**Post date:** [July 20, 2000, 12:43pm UTC](https://boards.straightdope.com/t/heater-works-better-with-lights-on/26227/3 "2000-07-20T12:43:42Z")

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Yeah it’s a seperate heater, it still gives off heat.

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**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\
**Post date:** [July 20, 2000, 12:53pm UTC](https://boards.straightdope.com/t/heater-works-better-with-lights-on/26227/4 "2000-07-20T12:53:01Z")

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Are you sure it’s not a heat-lamp, and not a regular light bulb? The light itself might give off a fair amount of heat. What size bulbs do you have? A 150W bulb puts out 150 Watts of heat, for example. A portable heater might put out 500W to 1500W, depending on it’s setting and size. If you’ve got a oil-filled radiator-type portable heater, it would take it a while to heat up, and for the first 10 minutes or so, the light would be the primary heat source.

Arjuna34