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John Kogel

A general question about electric heat.

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I believe that electric heat is more efficient than fuel-burning furnaces, because about 100% of the electrical input is converted to heat energy.

I've also been told that a 120 volt heater is no less efficient than a 240 volt heater. I'm not sure about that one. So why use a 240 volt heater? Because you would need to run twice the current through a 120 volt device for an equivalent heat and that requires big wire. I think that's the reasoning there.

If a house is heated by electric baseboard heaters with thermostats, does it make any sense to turn off lights that are not being used?

Light bulbs give off heat, keeping the room warm. It seems to me turning the lights off will just cause the baseboard heater to come on sooner, expending the same amount of electrical energy.

By the same logic, the new fluorescent lights they're forcing us to install are simply going to increase the loading on the electric heat circuits, with no power saving, at least in the winter months. ??

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I believe that electric heat is more efficient than fuel-burning furnaces, because about 100% of the electrical input is converted to heat energy.

The equation is much more complex than that these days, or much more simpler, depending on how you look at it. There's fossil fuel efficiencies of gigawatt power plants compared to residential furnaces and then there's simply how much it costs to heat the house. If you've a wood burning furnace in your house and the wood is free, you can throw all calculations out the window.

I've also been told that a 120 volt heater is no less efficient than a 240 volt heater. I'm not sure about that one. So why use a 240 volt heater? Because you would need to run twice the current through a 120 volt device for an equivalent heat and that requires big wire. I think that's the reasoning there.

There no significant difference in efficiency between 120V and 240V electric heaters. The I square R losses are too small. Plug in radiant heaters put more of the heat on you where it counts instead of just dumping it into the air and are likely a better buy for your money.

If a house is heated by electric baseboard heaters with thermostats, does it make any sense to turn off lights that are not being used?

Light bulbs give off heat, keeping the room warm. It seems to me turning the lights off will just cause the baseboard heater to come on sooner, expending the same amount of electrical energy.

I turn light bulbs off because the cost of heat from them per kilowatt-hour is undoubtedly higher than the strip element in my electric central furnace, when you factor in the cost of the bulbs.

By the same logic, the new fluorescent lights they're forcing us to install are simply going to increase the loading on the electric heat circuits, with no power saving, at least in the winter months. ??

Yes, but that's likely cheaper overall if you do the math.

Marc

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I believe that electric heat is more efficient than fuel-burning furnaces, because about 100% of the electrical input is converted to heat energy.

But only about 1/3 of the fuel energy supplied to coal and natural gas electric power plants is delivered to homes as electricity. The rest is lost in transmission inefficiency. So that's a huge knock against electricity.

By the same logic, the new fluorescent lights they're forcing us to install are simply going to increase the loading on the electric heat circuits, with no power saving, at least in the winter months. ??

I would refer you to Home Energy magazine Nov./Dec. 2008, and a follow-up article in July/Aug. 2009. They make the point that CFL's save energy, but there is definitely a take-back effect of up to 40% in heating-dominated climates when switching to CFL's and giving up the heat generated by incandescent bulbs. Of course in cooling climates there's an extra boost in efficiency.

The follow-up article makes the point that the only situation in which switching to CFL's is less efficient is with an electric furnace with leaky ducts. An electric furnace with well-sealed ducts will still benefit overall with the change to CFL's.

www.HomeEnergy.org

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OK. We have Hydro electric up here, so there is no fuel burning to produce electricity. (You would think it would be cheap, produced by gravity, but not the case, which is another subject) So I'm not comparing different fuels here.

If I used plug-in 120 volt heaters in place of the 240 volt wallmount baseboards, I think I would need twice as many heaters plugged in, drawing double the current. There would be doubled losses in the wiring, which is heat lost in the wall.

Thanks, Steve, I'll take a look at that.

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John, if you plug in a 120V 1500-watt heater, you are heating up one hot leg and the neutral. If you plug in a 240V 3000-watt heater, you are heating up two hot legs and the neutral, which will be somewhat hotter than if only one leg were in use. There is just no appreciable difference in efficiency or output at all. 240V heaters are common because they produce more heat, and more heat is needed in some cases. I have a 240V 4000W electric shop heater instead of (3) 120V heaters because it's easier to install and operate as one unit. It doesn't cost more or less to operate.

In your case (and mine), the efficiency gains can be had if switching to a heat pump, where you can get 200-300% efficiency pretty easily.

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. . . If you plug in a 240V 3000-watt heater, you are heating up two hot legs and the neutral, . . .

There's no neutral in a 240v electric heating circuit. Just two hot legs.

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John, if you plug in a 120V 1500-watt heater, you are heating up one hot leg and the neutral. If you plug in a 240V 3000-watt heater, you are heating up two hot legs and the neutral, which will be somewhat hotter than if only one leg were in use. There is just no appreciable difference in efficiency or output at all.

See Jim's correction above.

No I think you should compare a 120v 1500W to a 240v 1500W. The 240 volt unit uses half the amperage to produce equal heat. That means cooler wiring. And less heat loss.

And if that is correct, then 240 volt baseboard heaters are more efficient heaters than 120 volt light bulbs, which answers my question.

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. . . I think you should compare a 120v 1500W to a 240v 1500W. The 240 volt unit uses half the amperage to produce equal heat. That means cooler wiring. And less heat loss.

The difference in heat loss is too small to be a realistic consideration. (Even if it weren't, the "heat loss" would probably end up contributing to household heating anyway.)

And if that is correct, then 240 volt baseboard heaters are more efficient heaters than 120 volt light bulbs, which answers my question.

They're more efficient in any case because the light bulbs are using some of their power to produce light, which, when veiwed in terms of a heating device, is wasted energy.

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They're more efficient in any case because the light bulbs are using some of their power to produce light, which, when veiwed in terms of a heating device, is wasted energy.

Or another way of saying it is light bulbs are designed to produce light with heat being a unfortunate secondary byproduct.

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They're more efficient in any case because the light bulbs are using some of their power to produce light, which, when veiwed in terms of a heating device, is wasted energy.

Or another way of saying it is light bulbs are designed to produce light with heat being a unfortunate secondary byproduct.

Except for the small amount of light leaving the house via the windows, there are no losses. Visible light becomes heat when it strikes anything that absorbs it, whether it comes from a light bulb or the sun.

Marc

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Leaving light bulbs to help spread the light -

I had been schooled, and believed, that trying to heat electrically was one of the most inefficient ways to heat. One reason for the heat pump was the thought/theory that if you had no other choice but to heat via electricity then running a compressor produced more more btus, per dollar, than strip heat (up to a given temp).

In trying to become a more understanding Irishman I'm open to further discussion (as long as it doesn't contradict my preconceived notions).

Any white paper?

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How about Easy Bake Ovens?

When I use a 100w bulb to bake my cupcakes, is that energy lost, or do I absorb it when I eat the cupcakes?

I'm sorry, I just can't help myself...........

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How about Easy Bake Ovens?

When I use a 100w bulb to bake my cupcakes, is that energy lost, or do I absorb it when I eat the cupcakes?

I'm sorry, I just can't help myself...........

I thought they just banned light bulbs in EasyBake ovens. This the one you got a couple years ago?

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How about Easy Bake Ovens?

When I use a 100w bulb to bake my cupcakes, is that energy lost, or do I absorb it when I eat the cupcakes?

I'm sorry, I just can't help myself...........

I'm not sure about that Kurt but you should call it out:

WASHINGTON, D.C. – The U.S. Consumer Product Safety Commission, in cooperation with the firm named below, today announced a voluntary recall of the following consumer product. Consumers should stop using recalled products immediately unless otherwise instructed. (To access color photos of the following recalled products, see CPSC’s Web site at www.cpsc.gov.)

Name of Product: Easy-Bake Ovens

Units:About 1 million

Manufacturer:Easy-Bake, a division of Hasbro, Inc., of Pawtucket, R.I.

[:-party]

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Leaving light bulbs to help spread the light -

I had been schooled, and believed, that trying to heat electrically was one of the most inefficient ways to heat.

Electric heat is 100% efficient for the end user. Any inefficiency occurs at the power generation plant and in the process of transmitting the electricity to the end user.

You're confusing cost with efficiency. In most parts of the country, the cost of heating with electricity, even at an efficiency of 100%, is greater than the cost of heating with gas at an efficiency of 80%. Sometimes vastly greater.

That's not true everywhere. In the nearby town of McMinnville, electricity is so cheap that the difference in cost between 80%-efficient gas heating and 100%-efficient electric heating is a wash. Gas systems aren't popular there because gas systems cost more to install, cost more to maintain, and don't last as long. In this town, all-electric heat pump systems are much cheaper than natural gas heating systems. The whole town is full of electric furnaces, electric boilers, electric radiant heat systems, and heat pumps.

One reason for the heat pump was the thought/theory that if you had no other choice but to heat via electricity then running a compressor produced more more btus, per dollar, than strip heat (up to a given temp).

That's true except for the no choice part. Heat pumps are sometimes the cheapest heating choice out there, depending on the relative cost of the fuels.

In trying to become a more understanding Irishman I'm open to further discussion (as long as it doesn't contradict my preconceived notions).

Any white paper?

You don't need one. It's a simple fact that there are practically no losses with electric heating. All of the electricity that you put into the system produces heat. To figure out whether or not it's cheaper than the alternatives, you only need to compare the efficiency and cost of those alternatives.

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I pay 6.8 cents per KW hour, that is pretty cheap. But then we have TVA power and that is another government boondoggle discussion for another thread or day. When I lived in MS, we paid .14 cents per KW hour.

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I pay 6.8 cents per KW hour, that is pretty cheap. But then we have TVA power and that is another government boondoggle discussion for another thread or day. When I lived in MS, we paid .14 cents per KW hour.

9.2 cents/KWH in south Louisiana.

Marc

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OK. We have Hydro electric up here, so there is no fuel burning to produce electricity. (You would think it would be cheap, produced by gravity, but not the case, which is another subject) So I'm not comparing different fuels here.

If I used plug-in 120 volt heaters in place of the 240 volt wallmount baseboards, I think I would need twice as many heaters plugged in, drawing double the current. There would be doubled losses in the wiring, which is heat lost in the wall.

Thanks, Steve, I'll take a look at that.

Your point about the losses in the wiring is important. As an example, if you had a 120-volt 1500 watt heater with a 5% voltage drop due to conductor and connection resistance, your heater would actually produce 1357 watts of heat. If instead you purchased a 240-volt heater and breaker and used the same wires that had produced that 5% voltage drop at 120V, you would get 1,471 watts of heat, an 8% improvement over the 120-volt version.

Voltage drop is the gift that keeps on giving - to the utility company.

Douglas Hansen

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Your point about the losses in the wiring is important. As an example, if you had a 120-volt 1500 watt heater with a 5% voltage drop due to conductor and connection resistance, your heater would actually produce 1357 watts of heat. If instead you purchased a 240-volt heater and breaker and used the same wires that had produced that 5% voltage drop at 120V, you would get 1,471 watts of heat, an 8% improvement over the 120-volt version.

Voltage drop is the gift that keeps on giving - to the utility company.

Douglas Hansen

I will assume that the 5% loss is that voltage drop which occurs outside the insulation boundaries of the house and is lost to the consumer. With unity power factor, power varies as the square of the voltage. 5% voltage loss leaves 95% remaining for the consumer's use. 0.95 squared is 90.24% which is the percentage of listed power developed by the consumer's heater. That comes out to 1,354 watts

A 240V, 1500 W heater with otherwise similiar design would lose only half as much voltage, 2.5 % leaving 97.5% of listed power for the consumer to heat his house. Repeating the calculations with the new percentage yields 1,426 W, an improvement of 72 Watts, about 5.3%.

Regardless of which calculation is correct, it is significant after all.

Marc

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Thanks for that. Now I wonder if I should step up the voltage to 480V? I have a box of old power transformers, old tube amp stuff. I could easily run a small heater on 400+ volts and have even better efficiency?

Actually I could just plug all my old radios and amps in and turn the baseboard heaters off. [:)]

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Thanks for that. Now I wonder if I should step up the voltage to 480V? I have a box of old power transformers, old tube amp stuff. I could easily run a small heater on 400+ volts and have even better efficiency?

Actually I could just plug all my old radios and amps in and turn the baseboard heaters off. [:)]

Sounds like a recipe for bar-b-que, the indoor type. [;)]

Marc

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Your point about the losses in the wiring is important. As an example, if you had a 120-volt 1500 watt heater with a 5% voltage drop due to conductor and connection resistance, your heater would actually produce 1357 watts of heat. If instead you purchased a 240-volt heater and breaker and used the same wires that had produced that 5% voltage drop at 120V, you would get 1,471 watts of heat, an 8% improvement over the 120-volt version.

Voltage drop is the gift that keeps on giving - to the utility company.

Douglas Hansen

I will assume that the 5% loss is that voltage drop which occurs outside the insulation boundaries of the house and is lost to the consumer. With unity power factor, power varies as the square of the voltage. 5% voltage loss leaves 95% remaining for the consumer's use. 0.95 squared is 90.24% which is the percentage of listed power developed by the consumer's heater. That comes out to 1,354 watts

A 240V, 1500 W heater with otherwise similar design would lose only half as much voltage, 2.5 % leaving 97.5% of listed power for the consumer to heat his house. Repeating the calculations with the new percentage yields 1,426 W, an improvement of 72 Watts, about 5.3%.

Regardless of which calculation is correct, it is significant after all.

Marc

Now that you mention it, there could be some losses in the wall wiring, alright. But it's tek cable, good stuff, and a tidy job of clamping it. [:)]

Click to Enlarge
tn_2011328185658_wallheat2.jpg

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Somebody got rid of their oil furnace and hired a guy to install baseboard heat.

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tn_201132819131_wallheat1.jpg

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