The cheapest type of electric heating?

purplerobbie

purplerobbie

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What electric heating is the cheapest to run?
The electricity in the marina is on a card system and it can get a bit expensive when it's really cold.
I have a couple of oil filled radiators at the moment but are they the cheapest type?
Or are the halogen lamp type cheaper or fan heaters? Or????
 
I've been thinking about this in connection with heating a flat.

Fan heaters: noisy, a stream of hot air coming out means a draught of cold air going in, so only good if you sit in front of it

Other heaters: you get out what you put in, ie put in 2kW of electricity and you get 2kW of heat energy out, regardless of whether it's oil-filled or not.
 
I honestly cannot see why there should be that much difference, really. Ultimately, all the energy consumed must be turned into some combination of heat and light - possibly the halogen lamps might be slightly less efficient if they are putting out much in the visible spectrum. It's a rather different question to other forms of heating which burn things - you waste energy in the hot exhaust gasses and there is scope for efficiency improvements there.

We prefer a fan heater when we are on the boat - by blowing the hot air around, you get a more uniform heating and avoid cooking in one place in order to avoid shivering in another.
 
We have a dehumidifier plus a fan heater. What surprised me (doh!) is the warmth that the dehumidifier chucks out as a by product of drying the air. I understand it uses a third of the power of the fan heater. It's enough to keep the chill off the oat and then we top up with the fan heater when necessary. Sorry it's not a very scientific answer but it works extremely well for us, 40 foot boat, full-time liveaboards.
 
We've tried both. With an oil-filled radiator the thing stays hot and radiates heat even after the thermostat has turned it off. With a fan-heater it's only hot whilst it's on, and as soon as it switches off you start to feel cold.
 
Tony Cross said:
We've tried both. With an oil-filled radiator the thing stays hot and radiates heat even after the thermostat has turned it off. With a fan-heater it's only hot whilst it's on, and as soon as it switches off you start to feel cold.
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But, as the law of conservation of energy (is that the third law of thermodynamics?) says, energy is neither created or destroyed - and, in practice, it all ends up dissipated as heat. Hence, one KWH of electricity into an electric heater of pretty much any type will emit the same amount of heat into your boat. Some may do it in a more controlled manner than others. Your oil filled radiator seems to be more efficient than the fan heater because it stays hot, radiating heat after you switch it off - but you are not taking into account the several minutes after it is switched on when it is consuming power but producing little heat. The fan heater is outputting heat within a few seconds of being switched on and stops as soon as it's switched off.
 
parsifal said:
I've been thinking about this in connection with heating a flat.

Fan heaters: noisy, a stream of hot air coming out means a draught of cold air going in, so only good if you sit in front of it

Other heaters: you get out what you put in, ie put in 2kW of electricity and you get 2kW of heat energy out, regardless of whether it's oil-filled or not.
Click to expand...

No thats not quite true.

Only thing i would suggest to the OP is that he finds out what charge the marina is making per unit above what they are purchasing it for. They are only allowed to make a small administration charge but some i hear are illegally profiteering.
 
Following on from the thermodynamic argument, the dehumidifier should actually provide more heat than the power it consumes as you gain the latent heat from condensation of the water vapour.
 
Dave_Seager said:
Following on from the thermodynamic argument, the dehumidifier should actually provide more heat than the power it consumes as you gain the latent heat from condensation of the water vapour.
Click to expand...

Good try, but in order to condense the water vapour, it has to do something. In the case of a traditional dehumidifier, it needs to refridgerate a heat exchanger to get it cold enough to condense out the vapour - even at 100% efficiency, that is going to consume the equivalent energy to that reclaimed in latent heat. In the case of a dessicant dehumidifier, it doesn't refridgerate anything, but it needs to consume energy to warm the air that will be used to regenerate the dessicant - again a consumption that will balance out any energy recouped from latent heat.
 
As maby says, regarding efficiency, it doesn't matter what kind of electric heater you use. Every Joule of energy that enters the boat as electricity, ends up as heat inside the boat (apart from light shining out of the windows). But by its very nature, a fan heater warms the air faster than a radiant heater, which depends upon solid objects in the cabin absorbing radiant heat, then releasing it by warming the air around it.
 
maby said:
But, as the law of conservation of energy (is that the third law of thermodynamics?) says, energy is neither created or destroyed - and, in practice, it all ends up dissipated as heat. Hence, one KWH of electricity into an electric heater of pretty much any type will emit the same amount of heat into your boat. Some may do it in a more controlled manner than others. Your oil filled radiator seems to be more efficient than the fan heater because it stays hot, radiating heat after you switch it off - but you are not taking into account the several minutes after it is switched on when it is consuming power but producing little heat. The fan heater is outputting heat within a few seconds of being switched on and stops as soon as it's switched off.
Click to expand...

That may be true on paper but you're assuming that each device is equally able to convert the electrical energy consumed into useful heat energy in the boat. The fan heater consumes some electricity running the fan for example, also the oil filled radiator transfers it's head to the room by convection and radiation, the fan heater transfers heat only by convection. The difference between heating a boat with one or the other is very noticeable whatever the law of tehrmothingies says... :)
 
Tony Cross said:
That may be true on paper but you're assuming that each device is equally able to convert the electrical energy consumed into useful heat energy in the boat. The fan heater consumes some electricity running the fan for example, also the oil filled radiator transfers it's head to the room by convection and radiation, the fan heater transfers heat only by convection. The difference between heating a boat with one or the other is very noticeable whatever the law of tehrmothingies says... :)
Click to expand...
The electrical energy consumed to run the the fan heater fan, ends up as heat just the same.
 
elton said:
The electrical energy consumed to run the the fan heater fan, ends up as heat just the same.
Click to expand...

as does all energy - the only difference really is the efficiency of delivering it where you need it. Your diesel fired Eberspascher is perfectly good at converting the stored energy in fossil fuels into heat, but it then ejects quite a lot of the heat out into the marina where the ducks and gulls might be quite grateful for it, but it's wasted as far as you are concerned. The difference with electric heaters is that the entire machine is located within the space you want to heat - efficiency really doesn't come into the equation - all the energy that reaches the heater is going to be converted into heat one way or another and all that heat will go into your boat. The only losses are the heating of the supply cables coming from the power station to your shore power socket - and that can be kept pretty low through a combination of thick cables and high voltage transmission.
 
maby said:
as does all energy - the only difference really is the efficiency of delivering it where you need it. Your diesel fired Eberspascher is perfectly good at converting the stored energy in fossil fuels into heat, but it then ejects quite a lot of the heat out into the marina where the ducks and gulls might be quite grateful for it, but it's wasted as far as you are concerned. The difference with electric heaters is that the entire machine is located within the space you want to heat - efficiency really doesn't come into the equation - all the energy that reaches the heater is going to be converted into heat one way or another and all that heat will go into your boat. The only losses are the heating of the supply cables coming from the power station to your shore power socket - and that can be kept pretty low through a combination of thick cables and high voltage transmission.
Click to expand...
It's not me you need to convince.
 
I suppose you could rig up a heat pump to transfer heat from the water outside the boat to the air inside the boat. Heat pumps consume maybe a quarter of the energy they transfer.
 
RAI said:
I suppose you could rig up a heat pump to transfer heat from the water outside the boat to the air inside the boat. Heat pumps consume maybe a quarter of the energy they transfer.
Click to expand...

There was a discussion round here not long ago of air conditioning systems that could be put into reverse - probably an expensive option to install on boats in northern waters where there really isn't a strong need for airconditioning, but may be a sound option for short Med winters.
 
Tony Cross said:
That may be true on paper but ...
... The difference between heating a boat with one or the other is very noticeable whatever the law of tehrmothingies says... :)
Click to expand...

I'm with the physicists in that it's obviously true that all the electrical energy - as near as damn it anyway - gets converted to heat whatever the heater. But nonetheless I think Tony has an undoubted point. I think the explanation is due to two effects (and I don't know their relative magnitudes):

1. The inside space of the boat is not a uniform temperature. And still air is not a bad insulator. So stirring the air around could mean that more heat is conducted to the outside than would be the case for a radiant heater. Hence fan heaters are likely to need more power to raise the temperature local to the heater to the same degree; and
2. We don't actually need heat anyway, it's all to do with subjective ideas of comfort. It's possible that a cosy area close to the heater at 24C say but only 14C everywhere else feels better than a uniform 20C. Or equally that radiation from a hot body on exposed flesh might contribute more to comfort than does simple air temperature: think how nice it feels outside on a sunny day even if the air is near freezing.
 
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