I have a small shed and a few extra solar panels (about 400 watts worth). It's a cold area and I'd like to just convert the electricity to heat. I thought maybe a dummy load would work.

Basically I'm looking for a simple way to convert 12 volt (or 24) electrical energy to heat. Anything I can do to heat the shed up would be great. I'd like an answer independent of building and electrical codes because whatever ideas I get I can look into how those fit. This is a very rural area.

  • 1
    400W is not much heat for an insulated shed, it'll give you around 1350BTU's of heat, while a typical kerosene heater will provide 24,000 BTU's. You might be better off with a heat lamp that you can direct where you'll be working.
    – Johnny
    Oct 6, 2018 at 0:23
  • How leaky is the shed? Any insulation? Oct 6, 2018 at 16:15

2 Answers 2


You could just use a 12V automotive heater like this on amazon (but really any store with auto parts should have them):

12V auto heater

The benefits are:

  • It's a tested heater that should not burn down your building (unlike a true DIY using some type of "hot box" that might even invalidate your home insurance)
    • Don't forget to keep flammable material well away from it or any heater / light bulbs
  • It's designed to use 12V from automotive-like batteries, that are often used with solar panels, so all you need is a 12V socket and it's "plug and play"

I'd recommend trying one out in person, I tried one once that was barely warm and you couldn't even feel the air a foot away, while others are almost like a hair dryer (but designed to run safely longer than a hair dryer)


You could use a dummy load or any sort of load that can safely handle the power without drawing too much current.

If you use some light bulbs, that would provide both heat and light. This is one application where incandescent bulbs are a good fit. Some people use them to heat chicken coops.

For better heat distribution, you can have a fan blow air across the bulbs. Any inefficiencies in the fan just result in more heat, so no energy is really wasted.

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