Heating Costs

[Wage Slave]

Is anyone aware of any solid work done on comparing the cost of running kerosene fan heaters with airconditioners running in heating mode? I did some back of an envelope calculations a few years ago which supported the conventional wisdom that kerosene was cheaper was in fact correct.

Since then the cost of kerosene has increased by a good 50% and the cost of electricity has also increased but I suspect by not nearly as much. Or am I wrong?

Please. No suggestions that I should build a brick encased wood burning stove or something - it's not going to happen.

[wagyl]

I have the feeling that so much of this will depend on the efficiency of your heaters and their placement, that really the best you can do is to rework your back of the envelope figures with the current prices, for the level of heating that makes you feel comfortable. The price of kerosene seems to have an annual rhythm as well and I have a large tank here so I bought a years supply about 6 weeks ago.

[Wage Slave]

I think Gramps has a big tank as well - Perhaps that would be a good idea and it would certainly save me the weekly trip to the petrol station as well as allowing for buying when the price is a bit more attractive. How many litres? 400 or so? No-one around here has one though so don't want to start the neighbours gossiping.

As for calculations I think kerosene for my main room (18 tatami) costs about 20 Yen an hour to run at the current price. The problem is I don't have an accurate(ish) figure for how much power the air conditioner actually uses to do the same job. I know how much it can consume running full tilt but not how much it does consume to keep 18 degrees or so, if that makes sense. If anyone can find anything in Japanese that gives even rough estimates or example comparisons ....

[Russell]

I think Gramps has a big tank as well - Perhaps that would be a good idea and it would certainly save me the weekly trip to the petrol station as well as allowing for buying when the price is a bit more attractive. How many litres? 400 or so? No-one around here has one though so don't want to start the neighbours gossiping.

As for calculations I think kerosene for my main room (18 tatami) costs about 20 Yen an hour to run at the current price. The problem is I don't have an accurate(ish) figure for how much power the air conditioner actually uses to do the same job. I know how much it can consume running full tilt but not how much it does consume to keep 18 degrees or so, if that makes sense. If anyone can find anything in Japanese that gives even rough estimates or example comparisons ....

Use of electricity by your aircon depends on the size of the room, isolation, etc.

If your aircon runs on 100 V, then you can buy an electricity meter. Tells you exactly how much electricity you use.

I bought one at Don Quichotte.

[Wage Slave]

I think Gramps has a big tank as well - Perhaps that would be a good idea and it would certainly save me the weekly trip to the petrol station as well as allowing for buying when the price is a bit more attractive. How many litres? 400 or so? No-one around here has one though so don't want to start the neighbours gossiping.

As for calculations I think kerosene for my main room (18 tatami) costs about 20 Yen an hour to run at the current price. The problem is I don't have an accurate(ish) figure for how much power the air conditioner actually uses to do the same job. I know how much it can consume running full tilt but not how much it does consume to keep 18 degrees or so, if that makes sense. If anyone can find anything in Japanese that gives even rough estimates or example comparisons ....

Use of electricity by your aircon depends on the size of the room, isolation, etc.

If your aircon runs on 100 V, then you can buy an electricity meter. Tells you exactly how much electricity you use.

I bought one at Don Quichotte.

And depends on how cold it is of course. The figure I gave for kerosene is for the coldest months - January/February .

The meter idea sounds perfect - I can run one for a week and then the other and compare costs very accurately. Unfortunately the particular aircon I want to measure is a 200V job. I wonder if Amazon has anything?

[wagyl]

It is a 500 litre tank, and I do pay a little over petrol station prices to have that delivered by tanker. It is only used to heat a single 12.5 mat but high ceilinged room in a drafty old house, at fairly conservative temperatures, and is turned off while sleeping. I think if I was trying for 18 degrees in the middle of winter it would probably end up running full bore full time. This is in an area where puddles of water regularly freeze in the kitchen sink in winter, washing can freeze-dry in the engawa and the toilet bowl freezes once or twice an average winter. Last winter was no so severe and I used 350 litres. I do not have an air conditioner so I don't know how reverse cycle would compare here but I suspect that the snow build-up from drifts would interfere with the external unit and possibly ambient temperatures here would often be too low for it to work effectively.

The kerosene fan heater does have the benefit of being able to direct warm air down a duct to under the kotatsu, with a substantial saving of electricity, return on investment in about 2 months.

Also, that calculation does include about three weeks every winter where the house is abandoned and left cold.

Anecdotes in blogs (and I don't think you will get more than that)
http://hirara.seesaa.net/article/322388123.html
http://bizmakoto.jp/bizid/articles/1202/22/news055.html
http://www.dac-japan.com/kounetuhi.htm
http://matome.naver.jp/odai/2135825516504108001
and so on found by searching "暖房　エアコン　灯油　比較"

[Wage Slave]

Hmmm

Is this one 5 amps or 10 amps?

[Grumpy Gramps]

I think Gramps has a big tank as well

Big is relative, even more so in Japan My tank capacity is only about 120 litres, by far not enough for a whole season. So have to ferry some with my 7 jerrycans now and then. Apart from not having to run to the gas station all the time, the best cost-effect of this is to fill the tank and all jerrycans up to the brim in spirng and have the first ~240 liters of this season for last year's money.

Wifey, though, has been thinking about gas heaters for a while. Not sure, how that compares. My thoughts would first go to double-glazing / better insulation as that would help in summer, too.

But then, I have no meaningful numbers

[Wage Slave]

Here's some food for thought ....If Google translate serves it seems to claim that unless it is really cold airconditioners are a lot cheaper to run ...Mind, I don't think his figure for kerosene is accurate. At 70 Yen a litre he seems to be saying that a fan heater will use nearly half a litre per hour. I'm sure it's nothing like that even for a big room.

http://www.towntv.co.jp/2010/04/danbou-main.php#fffan

However he is also saying that 500 watts an hour is reasonable for an air-conditioner to do the same job - In that case, why am I lugging kerosene around?

[Grumpy Gramps]

70 yen a liter would be fabulous. In my area, the price for an 18 liter jerrycan hovers just below 2000 yen right now, which is closer to ~110 yen/liter. I have a fairly modern fan-heater in my office, which also serves another room and then some space, an area of ~16 to 18 tatami I guess.

At the beginning/end of the season, when there's only a light chill to fight, the 9 liter tank lasts a week or more easily. But when the temperatures go down to about 0°C, half a liter per hour is probably about right.

But then, I don't have it on 24/7, turn it off when I leave the room and overnight, or it turns itself off after three hours of no attention. If I ran the aircon, I would probably turn it on and forget it all day long, so there would likely be more operating hours/season.

[Wage Slave]

It's gone up a lot. From 65 Yen or so to just under 100 around here if you go to the self serve petrol station to get it.

It all depends on size, how warm you keep the room, how good the insulation is and outside temperature of course. I too get through about two tanks a week in Jan/Feb but the thing is running pretty much non stop - a good 90 hours a week. Perhaps our insulation is better than I thought.

What really counts though is the relative running costs rather than the absolute and it looks like aircon may be a lot cheaper. As the article points out though, the replacement cost of the machine is much higher - and that needs to be considered.

[Russell]

As the article points out though, the replacement cost of the machine is much higher - and that needs to be considered.

But you can use in the aircon in the summer for cooling, so this is a non-argument, unless you live in a place that is already cool in the summer.

[Wage Slave]

As the article points out though, the replacement cost of the machine is much higher - and that needs to be considered.

But you can use in the aircon in the summer for cooling, so this is a non-argument, unless you live in a place that is already cool in the summer.

True, but if it is used for heating as well as cooling it will last half as many years before needing replacement. The heating wear and tear can be done with a kerosene heater which costs at least 160,000 Yen less to replace for 18 tatemi.

[Yokohammer]

As the article points out though, the replacement cost of the machine is much higher - and that needs to be considered.

But you can use in the aircon in the summer for cooling, so this is a non-argument, unless you live in a place that is already cool in the summer.

True, but if it is used for heating as well as cooling it will last half as many years before needing replacement. The heating wear and tear can be done with a kerosene heater which costs at least 160,000 Yen less to replace for 18 tatemi.

Thinking about it, you know I don't think I've seen an air conditioner actually fail completely in the last 20 years or so. The built-in system we had at the house in Yokohama ran for the entire almost-20-years we were there (although it was stupid expensive to run), and the el-cheapo Corona unit that the previous owner of our current house installed in 1998 is still running just fine ... although I've had to beef up the laughably bad installation job he did. So that's been running for 16 years. I'm not sure it's even worth worrying about the longevity of these things any more. The only real issue is that an aircon from, say, 15 to 20 years ago is likely to be a lot less efficient than a new one.

[Wage Slave]

As the article points out though, the replacement cost of the machine is much higher - and that needs to be considered.

But you can use in the aircon in the summer for cooling, so this is a non-argument, unless you live in a place that is already cool in the summer.

True, but if it is used for heating as well as cooling it will last half as many years before needing replacement. The heating wear and tear can be done with a kerosene heater which costs at least 160,000 Yen less to replace for 18 tatemi.

Thinking about it, you know I don't think I've seen an air conditioner actually fail completely in the last 20 years or so. The built-in system we had at the house in Yokohama ran for the entire almost-20-years we were there (although it was stupid expensive to run), and the el-cheapo Corona unit that the previous owner of our current house installed in 1998 is still running just fine ... although I've had to beef up the laughably bad installation job he did. So that's been running for 16 years. I'm not sure it's even worth worrying about the longevity of these things any more. The only real issue is that an aircon from, say, 15 to 20 years ago is likely to be a lot less efficient than a new one.

Good point. PiL's place have units that look as though they were fitted in the golden days of Showa - and they still work. They don't use them much at all though.

[wagyl]

The other thing often forgotten in these comparisons is comfort level. If your feet and hands are warm, you soon feel comfortable. My thoughts are that reverse cycle air conditioners provide their heat from too high a location and they have to heat down to where you will feel it, whereas the kerosene fan heater can be more easily adjusted to provide heat where you want it and you may well feel more comfortable at a lower temperature. The kotatsu duct http://www.amazon.co.jp/gp/product/B001 ... N3Y6JHHWKN really emphasised that. The efficiency of the air conditioner in question has been raised again too, and that is a big factor. I think you are really only going to be able to answer this for yourself by buying that meter and doing practical tests.

[Wage Slave]

I think you are really only going to be able to answer this for yourself by buying that meter and doing practical tests.

I think you are right - I'm going to need to trial it properly. Thinking about it, I don't need to buy a meter really for the level of accuracy I need. With some care and faffing there is no reason I can't use KEPCO's meter.

1. Fill all the Kerosene tanks. Run a normal day using them taking a note of the start and end readings and times on the meter. Refill the kerosene tanks taking a note of how much it takes to top them up.

2. The following day use only the airconditioners for heat trying to mimic the usage as closely as possible. Take a note again of the start and finish times and meter readings.

With that data I should be able to get a pretty good idea of the relative running costs. I suspect more and more that aircons are going to win this handily so as long as people wear thick socks and possibly slippers (guilty) it is going to be the way to go. And I won't have to lug kerosene around the place either.

The temperature here rarely falls to zero during waking hours around here and airconditioners have the benefit that they can extract some useful heat from the environment via the radiator/fan in the compressor unit if it is at least 5 outside.

[wagyl]

airconditioners have the benefit that they can extract some useful heat from the environment via the radiator/fan in the compressor unit if it is at least 5 outside.

Well that rules that option out for me! (I was aware of the fact that the heat pump operation would fail through the ambient temperature being cooler than the range of the heat transfer medium anyway)

[Wage Slave]

airconditioners have the benefit that they can extract some useful heat from the environment via the radiator/fan in the compressor unit if it is at least 5 outside.

Well that rules that option out for me! (I was aware of the fact that the heat pump operation would fail through the ambient temperature being cooler than the range of the heat transfer medium anyway)

I think they will still work but not nearly as efficiently because the compressor will have to do all the work. Burning stuff might well be the better option in your case - at least in for the coldest two to three months.

[wagyl]

If the operating temperature of the refrigerant in the heat pump is greater than the ambient temperature, it is not going to be able to extract heat from the ambient. Unless by "the compressor will have to do all the work" you mean the only remaining source of heat is the heat waste from the electric motor doing the pumping and maybe operating the fan, in which case you will be seeing no efficiencies over those of an electric bar radiator. Albeit one placed outside your house in the garden. When the fan isn't iced up, that is.

[Wage Slave]

If the operating temperature of the refrigerant in the heat pump is greater than the ambient temperature, it is not going to be able to extract heat from the ambient. Unless by "the compressor will have to do all the work" you mean the only remaining source of heat is the heat waste from the electric motor doing the pumping and maybe operating the fan, in which case you will be seeing no efficiencies over those of an electric bar radiator. Albeit one placed outside your house in the garden. When the fan isn't iced up, that is.

That must be right with the qualification that we are talking about the temperature of the refrigerant in the outside radiator not in other parts of the system. Given how well freezers work I would have thought that that can be dropped to -5 at least and perhaps lower with a good compressor. However, decreasing returns are clearly setting in and at some point burning stuff is going to make a lot more sense. Anything much below about 5C as a rule of thumb? I'm not sure.

How cold does it get where you are?

[wagyl]

Lowest minimum recorded is about −20, and we get a -15 almost every year. I have an indoor temperature display on my fan heater which goes down to 6 degrees and for three or four months it is rare that I wake up and it displays anything other than L, meaning below 6 degrees. As I say, the kitchen is demonstrably below freezing for much of the winter, and occasionally the toilet bowl will have a crust that the blood-temperature new additions I introduced to it just won't budge.

In other words, I'm not looking to install a heat pump based on ambient air temperature.

[Wage Slave]

Lowest minimum recorded is about −20, and we get a -15 almost every year. I have an indoor temperature display on my fan heater which goes down to 6 degrees and for three or four months it is rare that I wake up and it displays anything other than L, meaning below 6 degrees. As I say, the kitchen is demonstrably below freezing for much of the winter, and occasionally the toilet bowl will have a crust that the blood-temperature new additions I introduced to it just won't budge.

In other words, I'm not looking to install a heat pump based on ambient air temperature.

I'll say! Crikey.

[Wage Slave]

So reading a bit more especially here, it would appear that the best strategy is to use aircons earlier and later in the season, switching to burning kerosene for the coldest months.

Apparently at 8.3 degrees or above an air source heat pump is working at 100% of its potential efficiency and is pretty efficient indeed. Below that it falls reaching 60% at 0 degrees. So, it would seem my rule of thumb of about 5 degrees to switch over is probably about right. So, for now, I'm going to use aircons and just monitor their consumption with the main meter to make sure I'm not making a mistake.

[Yokohammer]

So reading a bit more especially here, it would appear that the best strategy is to use aircons earlier and later in the season, switching to burning kerosene for the coldest months.

Apparently at 8.3 degrees or above an air source heat pump is working at 100% of its potential efficiency and is pretty efficient indeed. Below that it falls reaching 60% at 0 degrees. So, it would seem my rule of thumb of about 5 degrees to switch over is probably about right. So, for now, I'm going to use aircons and just monitor their consumption with the main meter to make sure I'm not making a mistake.

This makes a whole helluva lot of sense. Very good info.

I've been doing almost exactly that "by feel" for years. At some point the aircon just doesn't do it anymore ... usually late November or early December ... and that's when I switch to kerosene. Then in March when things start feeling a bit warmish I go back to the aircon for maybe a month or so.

Gorgeous day today, though ... which I'm spending in the workshop with the doors and windows open, so there'll be some photos in the "Tinkering" thread this evening.


Sent from my iPad using Tapatalk

[wagyl]

The same goes for Eco-cute hot water systems which are similarly no more than ambient air source heat pumps, running in the night time during the coldest part of the day.

[Russell]

The same goes for Eco-cute hot water systems which are similarly no more than ambient air source heat pumps, running in the night time during the coldest part of the day.

So, what you are saying is that they should be run at daytime during the colder months?

[wagyl]

The same goes for Eco-cute hot water systems which are similarly no more than ambient air source heat pumps, running in the night time during the coldest part of the day.

So, what you are saying is that they should be run at daytime during the colder months?

It depends if the efficiency losses from cold ambient air negate the savings that come from off-peak power rates (Most people with eco-cute are all-denka houses). It makes it a little hard if you have no gas booster heater on those really cold winter mornings. it would be a bracing shower!

[jingai]

To answer the original question, I modified a US-specific calculator for Japan using the best (if somewhat limited) info I could get about the efficiency of various options here. I'm trying to find a home for the article I wrote that goes along with it, but if you'd like the calculator to tweak with your assumptions, send me a private message. The short answer is that at least in the Sendai area and south, a decent aircon should be cheaper to run than a kerosene heater but at a much steeper upfront cost (though with benefits like no CO, fuel deliveries, fires, or dumping large amounts of moisture into the air.) The trickier part of the calcuation is adjusting the aircon performance based on climate. I have decent info on this for the US but have found no similar info for Japan and the industry uses Tokyo's climate as a reference, so my attempt to solve this is basically playing match the climate between locations in the US and Japan using weather station average annual heating degree days.

I think even in the heart of winter a decent aircon should work fine until night, and you could switch to kerosene as backup if needed for supplemental heat. The Wikipedia article mentioned doesn't seem to distinguish between (central) air source heat pumps from far superior ductless minisplits, and its info about cold weather performance cites a Canadian study on commercial units from 2002! Much has changed since then (heck, even since 2009.) Modern Mitsubishi and Fujitsu units ought to perform (COP > 2) down to -15 C or so. They do in the US. 5C should not be a challenge for any modern unit.

The aircon I bought also gives daily readouts of the electricity it uses (I couldn't find a basic external meter that works with 200V so this is a nice feature.) I plan to do a follow-up after this winter showing real world usage in coastal Tohoku vs a comparison of electricity used per heating degree day. If everything I think turns out to be wrong I will post that too!

[Russell]

To answer the original question, I modified a US-specific calculator for Japan using the best (if somewhat limited) info I could get about the efficiency of various options here. I'm trying to find a home for the article I wrote that goes along with it, but if you'd like the calculator to tweak with your assumptions, send me a private message. The short answer is that at least in the Sendai area and south, a decent aircon should be cheaper to run than a kerosene heater but at a much steeper upfront cost (though with benefits like no CO, fuel deliveries, fires, or dumping large amounts of moisture into the air.) The trickier part of the calcuation is adjusting the aircon performance based on climate. I have decent info on this for the US but have found no similar info for Japan and the industry uses Tokyo's climate as a reference, so my attempt to solve this is basically playing match the climate between locations in the US and Japan using weather station average annual heating degree days.

I think even in the heart of winter a decent aircon should work fine until night, and you could switch to kerosene as backup if needed for supplemental heat. The Wikipedia article mentioned doesn't seem to distinguish between (central) air source heat pumps from far superior ductless minisplits, and its info about cold weather performance cites a Canadian study on commercial units from 2002! Much has changed since then (heck, even since 2009.) Modern Mitsubishi and Fujitsu units ought to perform (COP > 2) down to -15 C or so. They do in the US. 5C should not be a challenge for any modern unit.

The aircon I bought also gives daily readouts of the electricity it uses (I couldn't find a basic external meter that works with 200V so this is a nice feature.) I plan to do a follow-up after this winter showing real world usage in coastal Tohoku vs a comparison of electricity used per heating degree day. If everything I think turns out to be wrong I will post that too!

Interesting post!

What aircon did you buy?