12V heater run straight from solar panel

A big resistor that can dissipate a lot of power at 12V, sufficient to be a useful heater, is also a low-valued resistor, on the order of one ohm (approximately 150 watts). Making your own with resistance wire would probably be easier and less expensive than finding and affording a commercially produced resistor, marketed as such. Having a few coils wired in parallel is probably a good idea, too.

I'd think, for heating with solar power, that a solar water heater (as in a black pipe in a reflective trough or something similar) and a radiator of some sort would be more efficient and effective overall. The cost would probably be lower, too.

DarkSkySeeker wrote:

agesilaus wrote:
Even small 120 VAC heaters are 1200 to 1500 watts...

Thanks. Yeah, I was imagining a big resistor with a heat sink around it that would run passively. Perhaps I will find that.

That's what these electric heaters are. Resistor: NiChrome wire coil
Heat Sink: The surrounding air

The problem is that it takes many Joules to heat up that air and get ahead of heat losses thru the walls, air leaks and such. You can't sneak around the Laws of Thermodynamics.

Maybe something like this would work for you ....

12 Volt heat lamp

agesilaus wrote:
Even small 120 VAC heaters are 1200 to 1500 watts...

Thanks. Yeah, I was imagining a big resistor with a heat sink around it that would run passively. Perhaps I will find that.

Never encountered a heater that would run solely from solar.

Even small 120 VAC heaters are 1200 to 1500 watts, that's a lot more than most peoples solar can put out. Heating is energetically expensive as is cooling aka air conditioning. But here are what is offered on Amazon


Be careful some are deceptive, the one 'universal heater' for example uses hot water from the engine block and the 12V is to run the blower motor.