Flower Pots & Tea Lights Heater




Introduction: Flower Pots & Tea Lights Heater

About: hgv driver but only because it pays more than I can make otherwise

I found this in a review and had to try it out. A room heater made from a small roasting tray and its trivit two clay flower Pots 4 tea lights and a scrap of aluminium foil

Step 1: Burner

light your tea lights and place them close together in the middle of the roasting tray. Place the trivit so it is sitting on the edges of the roasting tray above the tea lights not sitting on its legs in the tray as it would normally be used

Step 2: Convector

Place the smaller clay flower pot (in this case a 5") over the lit tea lights on the trivit block the drain hole with a scrap of aluminium foil the empty case of a used tea light will do fine. This is important as it traps the heat in the smaller pot and causes the convection without it the bulk of the heat will go straight through both drain holes

Step 3: The Radiator

Place the larger pot (in this case a 9") directly over the smaller this acts as the radiator and heats the room. I tested this in the coldest room in the house the bathroom my tea lights were very cheap £1/$1.50 per 100 & burnt for a little over an hour this was long enough to drive the condensation off the window and make it noticeably warm on entering. My local bargain store is currently offering 3.5 hour tea lights for £2 per 100 or 8 hour ones at £3 for 30 so unless you need to leave it over night say to keep a green house frost free refueling is cheaper
Cautions this is a combustion heater using un sreened naked flames normal precautions to ventilation explosive atmospheres location etc should be observed,  both pots get too hot to touch so you will need an oven glove when changing the tea lights. Also because of this place it away from flammable materials on a non flammable surface as the roasting tray got pretty hot too

Step 4: Field Trial

I have now been able to conduct a better test of this heater.
My parents have an old touring caravan they used as a storage shed which is nominaly frost free and convieniently my father keeps a max/min thermometers both inside and outside of it.
I started my experiment just before 7pm (3 hours after sun set) by lighting a tea light in a holder in the house so I could observe how much fuel was left.
I then went out to the caravan and set up the heater on a steel tool box roughly in the middle of the van zeroed the recorder floats in the termometer the temperature was +6c lit the tea lights and closed up the van. I checked and zeroed the out side thermometer it was reading +5c.
2 hours later the tea light in the house was still burning and whilst all the wax was molten there was still about 3mm depth left note this light was the first lit and is from the same batch as the ones being used in the heater. I went to check on the heater the outside temperature was still +5c. Inside the van the temperature had risen to +9c its maximum according to the recorder floats. How ever one of the tea lights powering the heater had already gone out the other three were also closer to going out than the one in the house molten wax only just covering the wick support.
This trial supports my earlier observation that this heater whilst not fantastic could well be capable of keeping a green house frost free over night or the plumbing in an ouside toilet from freezing.
I clearly need to repeat this test with just 4 tea lights spread around the van to see if the convector radiator arangment of flower pots is a more effficient means of transmiting the energy from the flames to the air than just burning the tea lights alone.
The internal dimensions of the van are 4.3m,1.9m,1.9m, that is 15.52 cubic metres.
As yet un written up experiments on the energy out put of  these tea lights  suggests over 90% of the released energy from this heater has been lost



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    35 Discussions


    7 months ago

    I like this. I've seen the claims that a single tea candle will warm the house all night long, and I know better, considering the quantity of fuel and it's energy density.

    But now, during a winter season that is colder than normal, the wood stove is doing all it can to warm the old farm house, and the cooler corners of the house are truly cool! A small heater glowing on the floor in these cool corners may help out!

    A little more design time, and the grate that supports the flower pots would have wooden handles that allow lifting the grate with flower pots attached. A very simple wire "net" could hold the flower pots to the grate, and changing the candles would become a simpler task.

    Thanks for the inspiration!

    Do all the math. A btu is not a btuh. one btu one pound h20 one degree right. well one btu will also lift one pound of water 778 feet in the air.

    Right. Home furnaces are measured in btuh.

    Now the next part, figure the R value of the space you are trying to heat.

    1 reply

    A BTU a British thermal unit, and is an antiquated unit in Britain. I grew up with the ISO system. Which uses Joules for measuring energy, and Watts for energy over time, so in theory the confusion over is it BTU or BTU/h shouldn't happen with ISO units. As for do the math, I did do the maths its plural where I come from because there is always more than one equation to solve.

    Sorry but this thing can't work as promised. I see you did not post any test results like room tempertature and such. I made a video about my test of this device taking note of temperatures and such.
    Result: change in temperature room ZERO. Still make a nice hand warmer. You might try your gloves or socks over it but still I would not advice to do this for security reasons. In any case you cant' do more than that.
    The reason is simple. You got about 1BTU of heat for each candle you light. You measure the power of home heater by THOUSANDS of BTU. Cant' compete.

    The video is here (sorry, Italian only)

    10 replies

    I agree my test was un scientific set up in coldest smallest room in house( 2mx2m approx or 6'x6' approx NOTE the Approx and I know they are not exact conversions) with heating off and it is north facing after exausting one set of tea lights the room was noticably wamer. The pots were both too hot to handle sensibly with out protection and the roasting tray was about as hot as you would want to touch with bare hands. I have looked at the test you quote and note significant differences in the heater tested to the one I have shown it uses a single large candle jar as fuel, un shielded from draughts with a significant air gap between the top of the jar and the base of the clay pots which will result in significant heat loss, the whole point of this design as I understand it is it captures as much of the very limited heat out put of a candle(s) as possible and radiates it into the room in a more efficeint way. I will also take issue with the 1BTU per candle heat out put as you are claiming to be more scientific given that I've seen candles from 1/8" to a 45 gallon drum of fat with a 6" wick you can not make such a statement as all candles produce just 1BTU of heat ,not quite what you said but it appear you have little grasp of experimental variable.

    You are right but only on a few points. My statement on BTUs was an approximation since usually 1 BTU is approximated to the heat produced by the flame of 1 burning match. That fire is about the same of the one of the tea candles used. My candle hat 3 wicks, so it's about 75% of your head output. But my room was 1.5 sqm...
    Still... even if the candles where "super candles" capable of 10 BTU each, or even "magic candles" of 100 BTU each your output would be 400 BTU max (magic included) and is FAR lower of any stove that ranges 8000 to 16000 BTU usually. Otherwise we should tell all those engineers that work at heating companies how dumb they are producing such inefficient systems.
    Another version: in 1700/1800 scientists wrote about thermodynamics. They where able to produce steam engines and start the industrial revolution. Still they where so dumb to heat their houses with a fireplace or home stove! Does this make any sense? Not at all to me... Pots and candles have been around a few centuries now, and we get to this only after sending a robot to Mars? Hmm...
    Anyway, post me you video with some measurements, I'll be happy to look at it.

    a candle puts out 263 BTU or about 77w of heat. so 4 of them are ~1052 BTU or 308w of heat. There are 150w personal fan-heaters for cars that do warm it up given enough time, so i don't see it being that far fected that twice that would heat a small room, especially when combined with the convection design (letting more 'power' go to heat rather than pushing the air with the fan blades).

    BTU and Watts are different quantities' units. Can you provide the reference please?

    Thank you I appreciate your supporting statment I actually did this


    crude experiment to disprove the satment all candles only produce 1 BTU. I fully appreciate that 1 set of results is not scientificaly valid, I only did it to satisfy my self and I also noted that the tea lights don't last as long when used in the heater as they do alone so whilst the total energy released must remain the same the power out put in terms of J/s for the shorter burn time must be higher. I also concluded that Emc wasn't worth arguing with

    Data taken from? I probably found the NIST article where you got your data from but it refers to regular candles, not tea type.

    Never heard of 150w car heaters, may be 150W are enough in a car given the (hot) engine is running... Regular room heaters usually go by 1-KILO-W to 2-KILO-W, about ten times more. Convection does not "built up" heat, it spreads around what you have available (hence "diluting" it) .

    Any experimental observations?

    Here other points of view with interesting comparison with light bulbs



    How does one btu lift one pound of water 778 feet into the air???? Math. btu vs btuh, btu to hp. one btu is a four inch match burnt tip to tip, five sec maybe. tea candle burns for four hours one hour divided by 5 seconds 720btu x four candles = 2880 btuh Rough but simple conversion.

    Equal to about a 1200 watt electric heater,

    sincerely, retired boilermaker

    yes I know im three years late, I went sailing.


    HAHAHAHA.... very funny... so to speak.

    My pots got hot too, 80°C in 25 minutes and then, very slowly, a little over 100°C. But this means NOTHING. If you put a pot full of boiling water in a room, the heat of the water is not enough to heat the whole room, while a bathtub could. A spark from a ferro-rod is over 10.000°C, does it heat a room? not at all. That's because temperature alone means nothing.

    Check again, time of the day, other possible heat sources like windows, the sun, someone getting a shower in those 3 ours...

    Can't go against math. But hey, if you really "believe" (faith is required here) this method, try relying on it this winter months and tell me about this experiment in spring. Nothing is better than a real test.

    oh but it does work.

    Before you make one of these - it does pose some health an safety issue as candles in general are a health problem - see this report


    2 replies

    I especially want to find inexpensive ways to bring heat to the
    developing world, where they burn plastic for heat. I assume these
    candles in terracotta, in their small homes, would be better for health
    and the environment than plastic, yes? Dealing with really poor people,
    so it needs to be as cheap as possible to get their buy-in.

    efficency of combustion is what is needed there. the simple teracota convector radiator principle could be used I guess but it needs a lot of work to find the optimal design. Candles would only be enviromentaly friendly if they are vegtable fat, bees wax or tallow.

    A few notes about this . I read your entire article. well done . very well researched. thank you for taking your time and doing it . I would adding a small :"Micro"Fan to push the warm air away to the rest of the room be a help ? instead of just attempting radiant heat ?

    again well done thank you for the information .

    1 reply

    Whilst a micro fan might be of assistance, I feel that adding electrics to it would negate it's simplicity. Using the internal convection currents to drive a turbine similar to those anoying candle chimes, which in turn drove a fan would be complex mechanicaly but wouldn't need any additional power source