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2002 Kenmore range using to supplement home heating.

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    Somebody has a lot of money to spend on their electric bill.
    – crip659
    Nov 25, 2023 at 12:01
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    You're asking the duty cycle of the heating element? It's not clear why you are asking that or what problem you want to solve. If it's an electric range that functions with the door open it will be 100% unless your entire home reaches 170 degrees. I think you mean something else? But you need to explain it better. Please edit the question.
    – jay613
    Nov 25, 2023 at 12:03
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    I'd suggest you consider another heat source. Thus is one of the most expensive ways possible to heat a home.
    – keshlam
    Nov 25, 2023 at 14:08
  • A small gas/propane heater(wall furnace) will probably pay for itself(including fuel) and heat much better than trying to heat a small room with an oven.
    – crip659
    Nov 25, 2023 at 15:55
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    To all who say this is an expensive heat solution: if OP lives in an area with all-electric energy and normally heats with resistive strips in an air handler, then this is no more expensive than their usual means. A heat pump would be much better of course if the thousands of dollars up-front installation cost can be managed.
    – Greg Hill
    Nov 25, 2023 at 16:20

4 Answers 4

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The range likely includes a thermostat that turns the element on if the oven is less than 170 degrees, and off if the temperature rises above it.

If you open the oven door and ventilate the oven cavity with a fan, the volume of air the element will be trying to heat consists of the entire house, give or take. The thermostat will test the temperature inside the oven, find it's less than 170 degrees, and continue to power the element. ie the cycle time would be 100%. Most ovens don't modulate, so your heat output is the rating of the element - might be 3kW or something like that.

This will continue until:

  1. The house reaches the temperature of 170 degrees, or
  2. The element burns out through over-use

I couldn't say how long such an element would last for when continually powered, but it is possible it will last for a long time.

What you've built here is a resistance heater; it's just a more awkward version of $20 fan heater, but is not inherently worse - the efficiency will be similar. The main advantage of that fan heater is the thermostat works at more human-friendly temperatures.

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    A fan heater can be moved to a bedroom or bathroom, the door closed, and it may actually have a chance of producing comfort. That's, um, one difference?
    – jay613
    Nov 25, 2023 at 17:39
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    I realise in 110V countries you can't just plug in a 3kW heater into the wall, you only get 1.5kW or whatever your plugs let you have. So a 3kW oven might have a slight advantage in terms of heat output. Terrible placement, though. Nov 25, 2023 at 17:40
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    Also fan heaters are notorious for starting fires, and are not rated for unattended use. But neither are ovens misused in this way. Nov 26, 2023 at 1:29
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Update based on actual issue: $6 per gallon for heating oil - a direct and immediate/obvious cost - vs. $0.12 per kWh.

One key assumption: 0.12 kWh is the total electricity cost and not just the "generation" cost. If you are not sure, take your total electric bill for one month and divide by the billed usage. That's the number you need to use, not just grab $0.12 from someplace on the bill. Distribution/transmission costs and utility fees and taxes can make quite a difference in the true per kWh cost.

Let's do the math:

Oil:

1 gallon of heating oil nominal BTU 138,000 for $6. Varies depending on grade.

Oil furnace efficiency - let's assume 80%, comparable to natural gas furnaces until relatively recently. Which on a quick search seems to be plausible, though there is a lot of variability depending on age of furnace, type of furnace and whether it is operating properly.

$6 / (138k BTU x 0.8) = ~ $0.054 per 1,000 BTU.

Electricity:

$0.12 per kWh = 3,412 BTU.

Efficiency: 100% (that is the nature of resistance heat, whether a toaster, a full size oven, a space heater or an "electric coil furnace". Note that heat pumps can be far more efficient.

$0.12 / 3.4k = $0.035 per 1,000 BTU.

So in theory using electric resistance heat will save almost 1/3 on your heating bill. That is really good. However:

An oven is not designed to be run 24/7, or even close. So I would factor in the cost of an oven replacement per heating season. That ain't cheap. In fact, for that price you can probably put in an equivalent amount of heat on baseboard or in-wall Cadet-style heaters (what Harper suggested). The heaters themselves are dirt-cheap, but you'll need some electrical work to get them properly installed, and that can add up pretty quickly - but that's a one-time cost, even if the heaters have to be replaced in a few years. They probably won't need to be replaced for a very long time as they are extremely simple and designed for high duty-cycle usage. The house I grew up in had them for decades, actually still in place when the house was torn down 40+ years later, though at some point my parents finally got natural gas (long story...). Unlike using an oven:

  • You have heat evenly distributed
  • The kitchen doesn't get overheated
  • You can still use your oven for baking food (wow, what a concept)

Also note that many ovens now have an automatic shutoff, typically after 12 hours. That is no big deal when you are baking - if you are really doing a marathon baking session just press a couple of buttons and you're back in business. It does cause a problem for Orthodox Jews using an oven over a holiday, which is why one of the features of "Sabbath mode" (really more of a holiday mode than a Sabbath mode, but I digress) is to temporarily bypass the shutoff setting. But for safety and reliability reasons, residential ovens simply aren't designed to run continuously.

Unlike space heaters, which are great for temporary use because they require no installation work:

  • Your house is safe
  • The heaters will likely last for decades - typical portable space heaters last anywhere from one year to several years depending on usage. Used constantly as a regular heat source, as opposed to occasional/emergency supplemental heat, they typically last a year at best.

The better long-term solution is to replace the oil furnace with a modern heat pump. That will save even more on energy costs, but has a significant up-front cost, typically in the $ thousands.


Don't Do This, Please

Note: This answer is based on the assumption that you need supplemental heat temporarily due to a problem with your regular heating system. If your regular heating system is undersized and you are not planning to replace it soon, get baseboard heat (cheap to install, expensive to run) or a mini-split heat pump (expensive to install, cheap to run). In other words, for anything except a truly temporary situation, see Harper's answer.

This is not inherently dangerous. But it is an inefficient way of heating your house in two ways:

  • Electric resistance heat vs. anything else

Electric resistance heat is generally much more expensive than heat pump heat. But a heat pump is not a quick or inexpensive fix for a broken furnace, and for all we know, maybe OP actually has a heat pump and is waiting for parts. In the short term, very short term, electric resistance heat can be an effective solution to either an undersized or, more typically, broken furnace or heat pump. So for the moment I would assume that the basic problem here is not a desire to really use an oven as a whole house heating system but rather a temporary fix - e.g., while waiting for repairs.

  • Directed Heat

An oven heats one place - the kitchen. In fact, many kitchens get overheated during normal use because heat is added from the oven (even with the door closed) and cooktop but the home temperature is regulated a room or two away with a central thermostat. Open up the oven door and now the kitchen will get far more overheated, but unless the kitchen is in the middle of the house and a very open plan setup, the heat will not easily move to the other rooms. You could easily end up 90+ in the kitchen, a comfortable 72 in some rooms and under 60 in others. This is really not a great solution.

A much better solution, if managed properly, is electric space heaters. There are many different models available. But the vast majority of plug-in electric space heaters:

  • Use ~ 1,500W of electricity - because that's the standard on a 15A circuit for continuous use.

  • Are very safe when used properly. Which basically means:

    • No extension cords (because of tripping hazards and because many extension cords can't handle 12A continuous usage)
    • Keep away from curtains, clothing, furniture, etc.
    • Keep small children and pets away from the heaters.
    • Do not run the heaters when nobody is home.

It makes no difference whether a portable plug-in electric space heater:

  • Has a fan or not
  • Has a "ceramic" element or not
  • Has visible coils (like a toaster) or not
  • Is oil-filled or not
  • Says that it heats a 100 square foot room or a 500 square foot room or anything in between

Just make sure that it is ~ 1,500W and is UL or ETL listed. Everything else is pretty much irrelevant. $25 to $200 - pretty much the same.

Two of those will roughly match the output of a typical oven. But the difference is that you can put one in the kitchen (if you need it) and one in a bedroom. Or two in separate bedrooms. Or one in the living room and one in the basement. Or whatever.

However, there is one big catch. An oven has a dedicated circuit. Most of the receptacles around your home are not on dedicated circuit. Most things you plug in to ordinary receptacles only use a few hundred Watts, many (particularly modern electronic gadgets and LED lighting) use well under 100W. But a heater basically uses a full circuit all by itself. So if you use more than one space heater at a time then you should check the receptacles and breaker panel to figure out which receptacles are on each circuit, and only put one space heater on each circuit. Space heater plus a few LED lights and a phone charger or laptop computer is no big deal. But two space heaters on the same circuit will lead to nuisance breaker trips at best and overloaded wires and a fire at worst.

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    Actual cost example:: My electric rate is about $0.17 per kWh (I pay extra for 100% renewable.) After all the additional charges, final real cost is $0.32 per kWh, not counting the $10/month fixed account fee. Be very sure you have included all those costs before comparing. They're almost certainly listed on your electric bill.
    – keshlam
    Nov 26, 2023 at 4:37
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    @keshlam Thank you. It is actually possible to have 0.12 kWh all-inclusive price in some areas with an excess of hydro or nuclear power. But less common than it used to be because (a) inflation and (b) if the generating utility can sell the power for more elsewhere then they will, which necessitates raising local delivery price too. On the other hand, oil price needs to include any delivery fees, etc. Nov 26, 2023 at 4:43
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Do not use electric space heaters

Or ovens, for that matter.

Electric space heaters cause thousands of fires a year - including, unbelievably, the worst railroad accident in Europe. They are not rated for unattended operation and people have gotten in big trouble leaving them run e.g. in baby's room. Everybody wants a Costco/Amazon silver bullet for their heating problems, but these are a disaster.

The oven is even worse, because aside from doing nothing for efficiency, you're also destroying the oven. It is running continuously without duty cycling, since it never reaches operating temperature.

Use: your regular furnace at higher duty cycle

Turn up the thermostat if that's what you want. Easy as that.

Why wouldn't you just do that?

"But I am emotionally loaded with the sense that turning up your thermostat will increase your energy bills" but the oven is not a cheat. It is guaranteed to be more expensive to run than the furnace, unless the furnace is electric and the oven is gas.

Use a heat pump, for Pete's sake

People get the crazy idea that the cheapest heater to buy must be the cheapest heater to run. The opposite is true. Resistance electric heaters are the cheapest possible heaters to make, as you'll see in the next section. To make a heater more efficient (cheaper to run) requires doing extra stuff, and that stuff costs more money.

And here we discuss the heat pump, which is an over-the-top example of this. The thing is an air conditioner run backwards, so heat is pumped the other way. It turns out they're pretty efficient, as in 200-600% efficient. In mild temperatures e.g. 50F/10C, they can bring in 6 times as much heat as an electric heater for the same amount of electricity. That's crazy cheap heat! But it costs more to install, although you only pay it once instead of getting bled dry by the utilities.

These come in increasingly affordable package styles, including the semi-DIY-friendly models such as Hitachi or Pioneer, and actual "window units" that mount in a window like an air conditioner.

At least, use baseboard heaters.

These things are the cheapest, and the least efficient - no moreso than the oven. But unlike the oven, they are completely reliable and will last 40 years or more. And unlike space heaters, they are UL listed for continuous use, unattended, as primary home heating.

The "Cadet baseboards" are my go-to… they cost as little as $75 for a 1500W heater. Not that much more than cheapo space heaters - and like I say, they last 40 years, in my experience cheapo space heaters don't last a season.

The only snag is they require professional installation and a 240V circuit. But that circuit can support 3840W (13,000 BTU/hr) powering baseboards in several rooms.

There are also permanently mounted in-wall or on-wall "heater fans" again of the 40-year persuasion.

This is not efficient, but it's always a better option than ovens or space heaters.

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Thanks to all for the detailed answers!

I live in the Seattle area and have an oil burning furnace. The price of diesel (fuel oil) is around $6 per gallon here thanks to all our carbon initiatives.

My average oil consumption is around 2 gal per day (30 degrees outside temp). So I am using about $12 of oil per day.

I pay around 12 cents per KWH for electricity.

So if my oven heating element is 3KW and I run it for 24 hours a day that would be 72 KWH per day. At 12 cents per KWH it would add about $8.64 daily to my electric bill.

I typically run the oven for heat for during the evening hours from around 6PM to midnight.

Using my oven on low with a fan blowing into it keeps my living area at about 70 degrees and the furnace does not run.

So, I think I will save money using this technique as long as diesel remains at this elevated price. If diesel comes down to $4 per gallon, I would break even with the "oven" method and would just use my furnace.

My main question was "how long does the oven heating element stay on at a 170 degree setting". What I gather here is that it makes no difference whether I set the oven to 170 or 350 degrees. The element will stay on all the time until the oven reaches the set temp.

Thanks again to all who responded!!! This is a great forum.

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    You'll be saving money until you have to replace your oven. Residential ovens are not designed to be run that much. Nov 26, 2023 at 2:44
  • Thanks. I use the oven for heat intermittently during the evening hours. I don't bake much so it gets moderate use. Worst case, I have to replace the heating element which costs about $30.
    – FRANK
    Nov 27, 2023 at 9:16

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