It’s my understanding that all convection 1500 watt space heaters whether big or small put out the same amount of heat. My little hair dryer is 1850 watts. If it didn’t burn out from overuse would it not heat the same space a little quicker than the space heater? 2nd question – I need to get a radiant heater since I hear it works better for spot heating quickly but wouldn’t it also heat the room as well as convection heaters so long as it’s the same wattage?
A hair dryer may well consume the same amount of power, but it will not shift as much air, so you’ll get a very hot and relatively narrow stream of heat, which in time will spread out.
Something like a fan heater will shift more air through it, this will not be as hot but it will mix into the room atmosphere faster.
The wattage rating would include the heating element and the fan. Although your hair dryer uses more energy, it probably requires more to run the fan at high speed than the heater would, so the energy consumed by the hair dryer is not as efficient in transferring that energy to heat. God that’s a mangled sentence. I hope you can decipher it.
I assume radiant heaters focus their energy to a particular location, as opposed to spreading the warmth. The only experience I have with radiant heaters is the noticeable glow I’ve felt walking past them in Costco, for example. It would make sense to me that this warmth should permeate to the rest of the living space. I can’t imagine where else it would go, so the wattage rating of radiant versus convection heaters shouldn’t matter, I would think.
These are my own unscientific meanderings on the topic only.
Yes all that power goes to heat - even power to the fan - the fan moves air so that is also a conversion to heat, so your hairdryer will produce more heat for that room as it is higher wattage.
But different devices will heat the room differently and on some you may feel warmer faster, which gets to your second question.
A radiant heater, one that glows orange, is great for uninsulated, drafty and even outdoor heating. The heat is transmitted by light through the air to the objects (and people), bypassing warming the air. For normal indoor living spaces some find the effect of such a radiant heater slightly uncomfortable, and also the orange glow may be undesirable in some applications. These are great for instant on heat and I do use one is a bathroom where I can turn it on and feel that heat right away and turn it off when I leave. I also like the orange glow in this application because at night I don’t want to turn on the full light but keep it dark. The orange glow is just about perfect for that.
A fan forced convection heater can also get warm air to a person very quickly and IMHO more comfortably then a radiant heater and I use that in my other bathroom. Both are suitable for instant on heat for one person at a fixed location like seated on the throne.
Whatever method you use, in the long term, steady state all will heat the room the same, the only difference is the short term use of how the room is to be heated. If long term continuous heating is a goal, as opposed to instant on, I would look for a quite (no fans) and non glowing one.
All watts are converted to heat, eventually. If the blow dryer consumes 23% more electricity (watts) then it’s going to put out 23% more heat and cost 23% more to operate.
Indeed - there aren’t many ways that an electric heating device can be lossy in terms of power consumed vs heat delivered - I guess if you had a really noisy heater, there would be losses if the sound escaped the room, but I suspect that’s a trifling amount.
Oh man, when I first read this I was like, “Yes, wattage = heat, eventually, so a higher wattage device no matter what it is will eventually add more heat than a lower wattage device even if it is a heater,” but I didn’t consider that some **sound **might permeate out of your house from a particularly noisy device like a hair dryer! Good call!!! Even if it is a trifling amount 
a radiant heater heats the people in its vicinity well and quickly. this can be energy saving because you do no need to heat the whole room, the air and far objects in a room can remain cooler. you set the heater for a level where you feel good near it.
a fan forced convective heater would make you feel warm quickly if you were near to the outlet of it. you would have to put up with a loud fan. the rest of the room would heat up gradually (hours).
unless you need the air and objects in a room to stay heated a radiant heater is far more economical of money and energy.
Hair dryers are not designed to be run at full power for long periods of time. There is an internal circuit that detects overheating and will shut it off. The dryer can’t be used again until it cools down. The older/dirtier the dryer is, the sooner this will happen. Maintaining good airflow is key.
(Thrift stores are full of old dryers that seem to work well in a quick test but once home you’ll find they shut off too soon to be useful. A good cleaning usually fixes them up.)
When I lived in my first (and only) apartment, I used to turn my hair drier on in the freezing bathroom before I took a shower. It worked just fine to warm the room up just above absolute zero, so I could take a shower without being coated in a layer of rime.
I think the biggest practical difference between hair dryers and convection heaters for space heating is that hair dryers are not designed to run very many hours. They have high speed electric motors that use brushes and commutators, and that tends to be a short-lived proposition.
You mean that isn’t a noise generator designed to make sure people shut it off?
You mean that they’re not making all that heat through the friction of poorly cast parts grinding against each other at high speed?
You mean that it isn’t converting energy to heat through a portal to the noise dimension?