Introduction: Flower Pots & Tea Lights Heater

Picture of Flower Pots & Tea Lights Heater

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

Picture of 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

Picture of 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

Picture of 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


Xonk61 (author)2018-01-13

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!

MarkP305 (author)2016-12-06

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.

Stan1y (author)MarkP3052016-12-07

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.

EmcySquare (author)2013-12-06

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)

Stan1y (author)EmcySquare2013-12-08

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.

EmcySquare (author)Stan1y2013-12-08

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.

LulzenbergB (author)EmcySquare2015-01-07

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).

MarkP305 (author)LulzenbergB2016-12-06

kudos my fine sir

chetaev (author)LulzenbergB2016-01-13

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

Stan1y (author)LulzenbergB2015-01-08

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

EmcySquare (author)LulzenbergB2015-01-08

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

MarkP305 (author)EmcySquare2016-12-06

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.

bbogle34 (author)EmcySquare2015-01-26


EmcySquare (author)bbogle342015-01-27

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.

MarkP305 (author)2016-12-06

oh but it does work.

chuckmccoy (author)2015-02-18

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

Idea Gal (author)chuckmccoy2015-03-16

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.

Stan1y (author)Idea Gal2015-03-17

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.

harthoppy (author)2015-02-26

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 .

Stan1y (author)harthoppy2015-03-01

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

chuckmccoy (author)2015-02-18

Stan1y (author)chuckmccoy2015-02-20

Don't quote other peoples research at me build it your self and test it for your self. I didn't belive it would heat a room either so tried it out.

I've only said it took the chill off a bathroom and suggested it could keep the frost out of a green house over night with longer burning candles, low power electric heaters are sold for exactly this. And I've come across many 1/4" or 1/2" wicked paraffin heaters that used to be used the same way, many used exactly the same burners as the paraffin road work marker lights. Indeed had my gandfather had acess to instructables he would have made one on converting such a lamp found with broken lenses by replacing the missing lenses with coco or treacle tin lids, to use as such.

chuckmccoy (author)Stan1y2015-02-20

No offense was intendended in my post however, the are references in it to very reliable research that cites serious helath issues regarding candles that people should be aware of. We are in the process of assembling one out if curiosity so we will see our results. I would think most people on here are open to additinal information and not be so uptight if some if it does not jive with their observations. My appologies.

Stan1y (author)chuckmccoy2015-02-21

Sorry I over reacted had a really crap day and just let lose.

Stan1y (author)2015-02-20

Shock horror candles burn!! produce carbon monoxide etc, can contain materials that maybe carcenogenic. I didn't need a 21 page paper to tell me that nor I suspect do most adults who have done science at 'O' level.

ewbray (author)2014-01-06

Found a way to have a much more STABLE base for the unit. I used an old 10 inch cast iron frying pan instead of the bread pan or meatloaf pan. Then fitted an upside down 8 inch round metal basket inside the cast iron frying pan that raised the flower pots level slightly higher (approx ⅞ of an inch) than the cast iron frying pan's edge's level to let oxygen to get to the flames. Cast iron frying pan's handle also makes it easier to move the space heater, {if necessary}, besides giving it a low circular heavy base that is NOT going to be tipped over!

To modify (compact) the source of heat, the next thing to do is to put the vegetable shortening in the empty 12 oz. tuna fish can and then put an old saucer in a frying pan that was half full of water. Once the water came to a boil, place the can of vegetable shortening on the saucer. As the vegetable shortening melts, vanilla extract or lemon extract is added to the solution; this gives the vegetable shortening candle a very nice aroma while it burns. Keep adding vegetable shortening and the flavor extract until the can is full to the brim.

Cooling the liquid back into a solid is best performed by either placing the can in the refrigerator and/or the freezer. After the solution becomes solid, push four (4) of the small birthday cake candles equidistant from each other into the matrix. The birthday cake candles supplies wicks that are better than any DIY homemade wicks.

By melting the vegetable shortening first, this REMOVES all of the air that the manufacturer places in the product during its production. This will help insure 5+ hours of burn time per oz. for each wick in the matrix.

Now there is one (1) fire unit, instead of four (4) separate fire units, that should give the user 10+ hours of continuous burn time for their flower pot space heater!

The 'secret' to good design of any device is to REDUCE the number of functioning parts down to the bare minimum!

If the user wants to stick more with the original design, the user could also make a {lamp oil and/or cooking oil} candle out of an old 2.5 oz. baby food jar X 4 and use those instead of tea lights since the user can get about 5 hours of burn time for each ounce of fluid! This way the user can refill the fluid candle bottles as needed and there is a much less chance of the heater being knocked over.

TheCoolDad (author)ewbray2015-02-01

An additional option, although, I can not speak to BTU's, or if it will work as well as candles, is to use/build a cooking oil candle. My wife found a commercially made set of these (I think they were popular in the 70's here in the US) and that's where the idea came from. Here's a link to how to make your own ( which, even though it is rather basic, it gets the point across. Also refillable and possibly even cheaper.

giffordr82 (author)2014-12-01

Can anyone suggest why the candles keep going out. I have used the above design so am stuck what Im doing wrong.. Thanks all

Stan1y (author)giffordr822014-12-02

The 2 things that come to mind are that there is either a seriouse draught (I conducted one of my trials in a closed bathroom the other in a caravan) and they are simply getting blown out. the second is insufficint air flow to maintain combustion this might be the case if you roasting tin is square. In a later experiment I conducted to establish the heat output of the tea lights I was using I discovered I needed eight 3mm diameter(57 square mm) holes top and bottom wouldn't support combustion but eight 6mm diameter(225square mm) holes did support combustion. The open vent on the top of the outer pot on my set up is only 22mm diameter which for me has proved adequate. a photo of your set up would help with suggestions

KevininWA (author)2014-11-11

I made this with a couple of modifications..I wrapped copper tubing between the pots that was fastened through the outer pot, and then attached a battery powered fan to the tubing, using a reducer fabricated from a 2 ltr. bottle and drilled a hole to match the tubing through the bottle cap. This made the outer pot a bit cooler to the touch, the inner pot is still quite hot because it is directly feeling the heat from the candle flame. The convection current still works its way past the copper tubing coils.. but in the end... I considered it a fail... too many gadgets.... The BTUs produced by the candles are unchanged.. and the best method of heat disbursement is the battery powered fan blowing against the outer pot.

morita.saito (author)2014-11-03

What a great idea....... I love this.

lyudmila.mitkova.5 (author)2014-10-05

Ok I made it!!! I used this model costed me 23 euros or 28 dollars. It is a nice looking "furnitur". Now about the job it's doing. I have 7m2 room in a big old house. Outside is now 10 C or 50 F. You will say it's not that cold, but it was a one night change form 29 C 84 F . It was 14 C in my room before I light up the heater, 3 hours later it's 18,5 C. It's still burning so it may get warmer. I will use it as an alternative. We turn on the central heater every night from 8pm till midnight. The flower pot will sustain the warmth till the morning when I go to work.

I do not imagine having to spend the hole winter entirely on candels, but it will work for what I need it.

Fikjast Scott (author)2014-03-03

This is so cool, the truck drivers would like this. When they get stuck in the snow, they use a coffee tin and candles. This would be great. Not sure if I would like the idea of having a burning candle in a truck.

Great project

Stan1y (author)2014-01-10

I've been experimenting with multi wicking using tuna tinsmy self but I am still trying to come up with a good method of apraising the heat out put of multi wick over larger single wick. The use of oil lamps is quite reasonable as the item that made me think this ideawas woth testing was the memory ofan old basic oil heater for keeping the frost out of a green house which was basicly a 1/4" parafin lamp as used to be used for road works in ametal radiator housing ratherthan a lamp housing.

Permahaven (author)2013-12-02

Great Idea, will try this out in my greenhouse next spring, when nights still are cold

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