Question for the Hive Mind

[grampster]

Question about electric infrared heaters. 

I have one that has 3 settings, I'm curious about two of them.  The high setting is at 1500 watts and the medium setting is at 1000 watts.  The desired temperature can be selected, and the heater shuts itself off when the desired temp is reached and turns back on when the room begins to cool back down.

In a modest sized room, 12x20, is it more efficient to use the high setting since the higher wattage heats the room quicker, and since the the unit turns itself off and then back on to maintain the desired temp.  It seems to me that would be the case as the lower wattage would take longer initially to heat the room and also longer bring the temp back up again after the room cools off and the heater comes back on.

 Or does it not make any difference at all even though it takes longer to initially heat the room, but at a lower wattage on medium balances that out. 

[Declaration Day]

I'm no expert but I assume that how well the room / house is insulated might play a role in the equation.

[Jim147]

Running my heater on medium seemed to save me a little on my electric bill so all you can do is try.

jim

[bedlamite]

Try it both ways and time it. I bet the duty cycle is 50% higher on the 1000w setting than it is on the 1500w setting. In the end, as long as the temp is the same, it probably won't matter.

[Ben]

One of my oil heaters is digital, and what it seems to do is run on high until the room gets up to thermostat temp, then it kicks on in a lower setting as needed to maintain temp. It's supposed to be an energy savings feature. Don't know if that helps you or not.

[230RN]

Running my heater on medium seemed to save me a little on my electric bill so all you can do is try.

jim

That might make sense if  you're on a demand metering system, where spikes in usage kick in a higher per kilowatt-hour rate, and 1500 Watts might just do that.  Depends on a lot of variables, including what else is running at the time.

This little doober can tell you a lot.  Keeps track of all kinds of electric energy usage measurements and you don't have to wait for a monthly bill.



http://www.p3international.com/products/P4400.html

$30 to $100 depending on features, but I'd shop around on line a bit.  This ad has an on-line manual and some other helpful discussions.  Moreover, by now, there are probably other brand names available --I don't know fer shore.

You might ask your friends if they happen to have one  you can borrow.  Mine was a gift from a son who knows I'm a bit of a fanatic about tracking down energy usage.  

Assuming a stable outside temp and wind and door usage, you can probably tell within a couple of hours fer shore which is cheaper.

Terry, 230RN

[Hawkmoon]

Infrared doesn't heat the air, it heats the objects in front of the heater -- basically, walls and furniture. My unscientific WAG is that the high setting is more efficient for heating up a cold room but, once the room is up to temperature, unless it's VERY cold outside I would expect the low setting to be more efficient in maintaining temperature.

[230RN]

On my ancient one, air also passes directly over the heating elements and picks up heat directly by contact (conduction).

It's got a little fan in it to enhance this effect.  Do modern ones operate exclusively by radiation somehow?

[bedlamite]

On my ancient one, air also passes directly over the heating elements and picks up heat directly by contact (conduction).

It's got a little fan in it to enhance this effect.  Do modern ones operate exclusively by radiation somehow?

A fan means it also heats by convection. If it has a sticker on it that says "caution hot" I bet it'll do conduction too.

[Brad Johnson]

Presuming the heater's output is sufficient to offset heat losses while staying within duty cycle, the wattage setting won't affect net energy consumption. The only differences a change in heating element wattage will make are how long it takes the room to come to temp and how often the element cycles to maintain temp.

My rationale... It takes a finite amount of energy to raise the room to a desired temp, and another finite amount per unit of time to maintain it at that temp. Heat loss from the room is also a constant (relative to environmental factors). In other words it will take X amount of energy to bring the room to temp, and Y amount of energy/hour to maintain it. You aren't changing the amount of energy used, just varying the amount of time necessary to inject that amount of energy into the space. Are there other factors? Sure, but they are negligible in terms of net effect.

An aside about the wattage thing. Really simple (read: cheap) heaters are direct-feed to the element. The element is off or on. Thermostats are simple bimetallic affairs that handle switching duty. More complex units will have electronically controlled variable outputs feeding the element. Does it make any difference? Not really. Electric heaters are essentially 100% efficient so it doesn't matter which type of element controls they use ("watts is watts"). Heat output for X amount of energy used will be the same. The only noticeable change is that one switches from ice cold to Surface Of The Sun when it cycles while the other is a bit less drastic.

Brad

[grampster]

Thanks for the info, hive.  At my age thinking about a thing usually leads to a nap, so it's better to ask those who know or at least stay awake long enough to guess.  Brad's comment seems cogent.

[Brad Johnson]

This popped up in my YouTube feed this morning. Explains the scenario much better than my rudimentary attempt above.

https://www.youtube.com/watch?v=V-jmSjy2ArM

Brad