I doubt I'll convince you otherwise, but while I haven't gone along with the whole "tea light" thing in whatever cultish forms it takes, I can attest that the pilot light of a propane heater is a viable source of heat under the right circumstances.
Actually that would take no convincing at all. I'm not smart but I can do a bit of research on the net and what I have looked at tells me that the pilot light on a water heater is worth a good number of KW per day.
I wondered about this when thinking about how the surface area in the heater which is used to transfer heat to the water could also radiate it back the other way and had a nice Chimney effect to do that. I pondered if the pilot light would offset that and tried to find something on it and there it was.
I forget the numbers now but I do remember it was significant and much more than one would assume.
If this was an indoor heater as my old aunt used to have and the room was small, then this could easily make a difference to the comfort level of a place.
Co levels may be an issue in a confined space depending on setup but that's another story.
And that's the thing, You don't have to be smart with this stuff, any pelican like me can look it up and find the truth even if it is different to what most people would assume.
One thing I see and strikes me a lot is with Slow Combustion wood heaters. People often Duct the flue out through a wall as soon as possible or straight up through the ceiling. No matter how efficient the firebox of the heater, there is still a HUGE amount of energy in the flue. -IF- I had one of these heaters, I'd run the flue to the other end of the room and back along the wall and then go up. I'd also put a small fan blowing along the length of the pipework to make sure the max amount of heat was extracted.
I verified my belief on this last year. Went and looked at a house where the owner had ducted the flue straight up from the ground floor through the floor in the first story and then out the roof instead of going out through a wall. He'd put a piece of stainless ( nicely Polished) around it leaving a gap forwards and had a couple of small fans on the back of the metal. The heat coming off that flue into the top floor was warming it beautifully. I think a lot of people stopped and looked at that and got a bit of an education. :0)
All that said, I'll leave it up to you to figure out how a whole 25W of battery power at night can let me cut the main propane burner off at night and let the main box cool down to save energy (and by extension in that case, *money*), all while making the difference that allows me to remain cozy in the process.
I guess we may get into semantics here but on this we may have a difference of opinion or terms.
And I have not looked this up but pretty sure the numbers would prove that 25W, the heat output of a tail light globe or around that of a candle, would not raise the temperature of a room in degrees as displayed on a thermometer on the wall, even a single degree in an average 9x9ft room with typical and realistic airflow.
Now, If you are using that 25W in heated clothing such as they wear on Motorcycles or for hiking, directly convecting that heat to your person, Different matter. As you mention battery power and I don't take you to be a person that believes in any of this fantasy over reality make believe, I suspect thats what you may be talking about and it is a realistic and creditable outcome.
I have asked all these proponents of tea light candles I have engaged with to tell/ show me how many degrees they raise the temp of a room on a thermometer. Not a single one has done that. Warming to me is doing that, demonstrating a temp on a devise made for that purpose. A thermometer.
If the source won't do that then to me, it's not doing it, belief is. If I can stick a thermo in say electric clothing and the thermo goes up, then to me that's realistic and factual. Electric blankets on beds are low powered as well but they too can keep you toasty warm at night and again, if you threw a thermo in the bed and measured the before and after temps you would see a difference.
Someone saying something does keep them warm but can't be demonstrated with a thermometer to me is just pure and utter crap.
I remember some years back going away for a baseball Tournament for my son. We booked this quaint little guest house just round the corner from the place that was also quite cheap. Unfortunately the place had no heating and the weather was getting down to a degree or 2 above freezing. Anymore than a single fan heater would trip the breaker and that wasn't nearly enough to heat the place to any level of comfort. After the 2nd time of resetting the breaker, I looked at the fuse layout and saw while all the lights and power were on one circuit, the Stove and bathroom heater were on separate circuits.
Came in, opened the oven door and turned that on and all the elements as well. Went in and turned on the bathroom heater and the place did start to become more comfortable. After a couple of hours the place had come up to 20oC so I backed the stove off a bit and stabilised the place at that.
as said, heat is heat and it's cumulative whatever the source.
A friend of mine in AC was telling me about a chain of Jewelry stores he had as a client. He had done the AC in a number of their shops some years back but they were now getting complaints the places were too hot even in winter with the AC on full tilt. He couldn't understand it at first how multiple units must be failing all at once.
When he went to look at the problem, he found they had remodeled said stores and were now running up to 20KW of incandescent lighting in these places completely changing the heat load he calculated when he installed the AC. What he had put in was now over taxed on the lighting let alone any other outside heat sources like people and weather. He said he always leaves margin for the inevitable overly hot days etc but more than doubling the lighting load was not something he took into account.
They didn't want to cut back on lighting or go to fluros so he installed another AC unit. Not cheap in a couple of the stores as new mains had to be put in to meet their power demands.
Hate to think what the power bill in these shops must have been!