Best Solutions for Battery-Operated Space Heaters

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1. A year ago we had severe storms ahead of an artic cold front. Needless to say we had an extended power outage with plummeting temps. I have a 1500wh maxoak bluetti lithium power station and 700 watts of solar to recharge it. It was a God send to be able to run 2 heater blankets and a small coffee pot. The heater blankets each used about 120 watts, but only about a 30% duty cycle set to “middle level” which was still very warm, so effectively 40w/h power usage each each. So for an emergency kit a person could get 1 heater blanket, 1 500wh power station, 1 -200w solar panel and have approximately 8-10 hours of warmth. A 200w solar panel could replenish the power station under a full day of sunshine. All this can be had for around $500-$700 if you shop around.

   I’ve since gone up to having 4000wh of battery capacity and about 1kw of solar.

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   1. Thanks for sharing your experience.

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2. Some people I knew that had outdoor doghouses used to make heaters by putting 100W incandescent bulbs under coffee cans, with a few small holes punched in them. The cans were securely bolted down. This would not generate a lot of heat, but would be enough to warm a doghouse on cold days. Something to consider I suppose.

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3. We have a space heater. When the electric goes off, our generator kick in within 15 seconds. We want to know what can be used to keep the space heater on and not loose the circuit when the electricity goes off. A power surge protector or a battery back up? We need the space heater to stay on. Any suggestions?

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   1. You should not use an electric space heater with a electric generator. In a nutshell electricity is still the worst selection for heating. Gas, wood, propane, geothermal and pretty much all other heat sources are better than using electric resistance heating. A better fix would be the “Mr Heater” series of indoor safe propane heaters is a possible alternative. If your heating system is natural gas or propane, you will need to get an electrician to confirm the load (20amp 120v or 20amp 240v and so on) and match your generator to that voltage and amperage. In general we recommend that you get the largest generator you can afford and consider a dual fuel unit (gas/propane) so that you can use either fuel source. I hope this helps, all the best.

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4. Hi! I have a user case that I would love some input on.

   I have an electric cargo bike (https://www.urbanarrow.com/en/family) that I use to haul the kids to kindergarden, school or just around town all year. Temperatures around here during winter are normally about -10 (celsius), sometimes reaching -20 or so. During the winter I use the rain cover on the bike (like a tent covering the cargo space) to protect them from the wind (and they are well clothed!), but I’m looking for something to make it a bit more comfy inside there.

   I have been googling around for a portable heater of some kind that does not require a mains connection and is safe to touch. Preferably something battery powered and small. That googling led me here. Still haven’t found a suitable product, though. I appreciate the math that makes battery powered heaters impractical as a way to emergency heat an entire home for extended periods, but in my case the space is small and it wouldn’t have to last very long. An hour or two would suffice, and I could recharge it again. Since these are kids I would need something that is safe to touch, and I would like to avoid gas. Doesn’t have to be electric though, I just thought that would make it easier/cheaper to reuse.

   Any ideas? A battery powered hair dryer or something? I’m thankful for any input!

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   1. August will weigh in on this in a bit, but how about going old school with a wool blanket and a foot warmer? That’s all the pioneers used back in the day when they were traveling in wagons. The Soft Comfort Hot and Cold Pack heats up in the microwave and holds heat for several hours. I use one in bed to warm up my feet when the temp drops. It’s a little more convenient than a hot brick, and a little longer lasting than a hot water bottle.

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      1. Thanks for the reply, and the idea!
         I already have a wool blanket for them, but I haven’t tried a foot warmer. I had in my mind something a little more like a fan, or something to heat the air inside the tent, but I’ll definitely look into the foot warmer. Thanks!

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         1. I can understand the inclination towards a warm air blower, as it would reduce the condensation inside the unit, but the physics of resistance heaters are no friend to battery life. I know when talking about running homes off of solar, one of the things they specifically tell people to avoid to reduce the load on their batteries is blow dryers. They are serious power hogs.

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         2. Alternate ideas
            (1) A wool blanket UNDER the people and two above
            (2) Two to four of the heating/warming packs Laurie mentioned would be very effective, small and multi-function (foot warmer, car warmer, urban-narrow warmer + cold pack for sore muscles/injury).
            (3) The small chemical warming packs are effective but would be fairly expensive.
            (4) A below zero sleeping bag – if you can fit a larger one consider TETON Sports Mammoth Queen Size Sleeping Bag or the smaller one TETON SPORTS Celsius XL
            (5) Any combination of the above.

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            1. Thank you, Laurie and August, for your input. I understand that my idea of a battery powered warm air blower won’t happen, but at least now I’m convinced it won’t happen because such a device doesn’t exist, not because I couldn’t find one on the net. All of your ideas are very good, and I will probably go for a combination of them. They already have a nice blanket over their laps when riding, but I could surely insulate the floor better, and give them some sheepskins to sit on and in their backs. Just to make the ride a little smoother and cosier. Not that there was any crisis to begin with; The kids are properly dressed for winter.

               Thanks again!

   2. Henrik, I do not have a manufacturer or link, but since your bike is powered, could you use a 12v powered heater connected to your battery? My DH has been experimenting with them in a van with no heat. They plug into the cigarrette lighter or similar 12v port.

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5. Hi. What about the self heating pet pads. Maybe wrap it with the blankets.

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   1. Yes, thank you. That is what we have in there now.

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6. There is no reason why a portable lithium ion battery powered heater shouldn’t exist I have a gaming laptop that fan exhausts a hell of a lot of heat that warms a small room and definitely a tent for about 4 hours from battery.

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   1. Yes it seems possible, but the physics is the problem. A single 18650 (common rechargable used in laptops and electric cars) has about 80 watts of energy or at the 5v about – 10 watt hours fully charged. That means you can pull 10 watts from a single 18650 battery for 1 hour; 2w for five hours, or 1w for 10 hours.

      We need roughly 40 to 50BTU per per square foot per hour to heat a home. Estimating 100,000 BTU per hour or about 29,500 watt hours. That means we would need 2900 fully charged 18650s to heat the house for 1 hour. You would need 24x that much for 1 day. So about 70,000 batteries costing about $279k for 1 day of heat for a small to medium house, more batteries and cost for a larger hours.

      Note: This is still not better than marine 12v batteries. A 12v marine battery is much larger but also provides 1300 watt hours (you would need about 29 of them). So either way it is still a very large number of batteries. Researchers are working on better batteries every day. We just need about 1000x increase in storage capacity and a corresponding decrease in cost and we will then be able to use them.

      So as of May 2018, wood, natural gas, and solar based heating all remain more effective than batteries by a huge factor.

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      1. I’m tallking about a small space for emergency heat like a tent or a well insulated small room even a 2kwh space heater would struggle to heat and maintain heat for entire home. My laptop draws 67-59 watts per hour from the battery at 100% load for roughly 4 hours until discharged I do not know what the peak output of the battery is but it is a hefty brick with quite a few cells I would have thought. What portion of that drawn energy is converted to heat I havn’t got a clue either but I do know it takes the chill from a small room and a tent so I could only imaging a similar battery drawing a slightly higher wattage but simply into a purpose built heating ellement with an efficient brushlesss fan or some crafty convection method other than a cpu, backlight and hdd’s would achieve better results in an emergency situation for a small space and for limited period.

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         1. Heating a tent with a battery powered solution is a possibility. A 4 person tent has 80 square feet of floor space. Assuming 40 BTU per square foot per hour that means at 80 sqft 80×40 = 320 BTU per hour or 32 used up 18650 batteries per hour. That is $127 worth of batteries per hour. For an 8 hour night that is about $1016. You are correct, it is possible, but it is fairly expensive. The good news is it could be reused IF you have power to recharge the batteries.

            If you created the unit, it would need to hold approximately 256 “18650” batteries (about 18 pounds + a resistive unit, estimating about 3 to 5 pounds – so about 21 to 24 pounds total) It would only work for 8 hours. Even if I over estimated by 50% it would be $508 in batteries and about 10.5 to 12 pounds for the unit. I am unsure how you recharge them when camping or in an emergency though, as a full day of sunlight is needed and a single portable solar panel could recharge 2 to 4 batteries. So you would need at least 32 solar USB charging units to charge the 128 batteries in one day (probably more). Ignoring cost, solar panels and weight – This solution would, and it would keep the tent warm. I still recommend a propane, rocket stove, wood fire or other simpler low grade heat source.

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7. As winter air is so dry, the moisture generated by propane heaters is usually welcome, if your space is not too small or air tight. We supplement with kerosene, and actually keep a pot of water on top of the heater to add some humidity to the air. Did the same when I had a gas stove, whether we had electric available at the time or not. I have always preferred when electric was out, to simmer water on the stove for heat rather than just running the gas oven. Now, THAT produces a lot of humidity! But also used the same method for additional/alternative heat when camping as well. Another tip, if you have electric, but your furnace is out, run your clothes dryer vent tube into the house rather than outside; again, it will be moist heat, but better than nothing!

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8. I got some pretty good heat from hooking up two 9-volt batteries together. Put them under a clay pot and was amazed at the heat produced. Don’t touch without gloves or you’ll get a severe burn.

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   1. Pretty sure this option would void any and all home insurance or renter insurance policies.

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9. Kayla thanks for your response. There are probably 2 or 3 cats under there. Yes I do know about the electric cat warming pads. The problem is we worry about a fire since the outdoor set is completely covered and tied down to avoid drafts. Also , electric outlet is too far. Can’t believe there are no battery powered heaters! Thank you so much.

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   1. If they could develop the mythical super battery from the movie “Knight and Day” (without the exploding part), then you’d be able to supply enough energy to make it work. Until then, we’re stuck with today’s physics.

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   2. I’m following this thread 4 years later, still hoping to find something for some ferals that live in my garage, I use the straw but it seems so harsh, poor babies. I have a message into a hothands website about a bigger pad they have advertised but there isn’t a size. I also like a previous comment on here that took me to Amazon.
      I have to research that further. Our temps the end of the week are down to 4 degrees.
      Time for me to invent something for our outdoor furbabies.

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      1. I know straw is generally recommended for ferals, but we have a mother/daughter pair that are doing fine in a wooden shelter tucked up close to the south side of our home with old blankets in it. Temps have dropped below zero overnight.

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10. I have a question. Hope someone can help out. We have a few feral cats who we know go under our canvas waterproof cover that covers our outdoor furniture set.. we secured the canvas so that it is sealed down as much as possible to avoid drafts underneath. We have also placed blankets and cat beds underneath. This year we went crazy and placed an old hot tub cover over furniture set and then the canvas on top of that. This concoction is sitting on our deck. We are trying to figure out how to provide some heat for the cats. We are not comfortable using any electric heaters under there or propane as we feel it would not be safe. Would love some suggestions. Thank you, Janet in Montauk NY.

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    1. What about something like a hot pack that you heat up in the microwave? Core products have hot cold packs that are filled with some sort of clay-like substance. I keep one in my bed to keep my feet warm, and it’s still holding a little heat when morning rolls around. Outside it would likely cool off faster, but at least it would be something. I’ve let Miss Kitty sleep on one with a blanket tossed over it, and she was very happy. Product link – Dual Comfort Therapy Packs 10″ X 13″

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       1. Another thought occurred to me overnight – do they have material to snuggle into? If they have old blankets or coats that they can snuggle into, they can conserve a lot of heat by curling up into a small protected ball.

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          1. Yes before we covered our wooden outdoor furniture we placed not only blankets on the chairs but also placed warm cat beds on each chair. Thank you for your concern. The feral cats that go under the set are now elderly. They were cared for and fixed by our neighbor before we decided to move here permanently. So cats have some enclosures filled with straw next door and our shelter as well. Both my neighbor and us feed the cats and make sure they have water. Was only able to get one feral cat to come in our house. The others are afraid. I would say there are about 7 feral cats outside. Just wish there was a safe solution to heating them under the canvas. Thank you so much for your kind thoughts.

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             1. They’re lucky that they have you to care for them.

             2. There are outdoor safe electric pet blankets.

             3. This is late, but did you try an incandescent light bulb? In a safety light so the bulb is protected? That would give off heat and if it’s well shielded from wind it might be enough. Some people use something similar for chickens.

             4. I think she didn’t want to use something powered.

    2. Hi u can try making a solar heater box its made from greenhouse panels, its inexpensive and easy to make. u can also put some rocks or bricks into the box to hold the heat after the sun goes down. The solar window box is being used to heat homes and used as a slow cooker. Check out this video it can explain it a lot better then I can. Its on YouTube (off grid window box solar heater doubles for a sun oven). Its uploaded by (Frugalgreengirl) I really think this can be helpful to u. Check it out its a very smart way to make heat and very easy to make the girl that did the video uses it to heat her home and cooks in it all done by the sun no batteries, electric and no gas all sun… I hope this will help u good luck ????

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       1. Thank you so much. I will look into this. I appreciate your concern and help.

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    3. You might try this as I’ve seen it online quite often. Take coolers, cut an entrance hole in the end, line with straw, not hay because straw stays drier and keeps moisture down. or storage tubs, line them with the board insulation and cut entrance holes as well and line with straw too. There’s videos online and they are amazing. It would also clear up your porch a little too and make more room for more ferals. I built the cooler one a few years ago and put it under our deck. It worked great. But for precise instructions look online like on YouTube etc.

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       1. Thanks, Janet.

          Here’s one of the videos:

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11. Burning 5 lbs of propane creates 3 lbs of water. Any propane heater not vented outside will make everything damp including your clothes and make you loose body heat faster and cause mold and mildew.

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    1. Burning propane does generate water vapor, so it’s important to a) size the unit correctly for the space b) run it according to manufacturer’s instructions. These units are not meant as a full time heating option in a tightly sealed building. They’re more commonly used for short term emergency heating, or for camping or hunting shacks that have more natural ventilation. I asked my friend CJ (who supplied the Buddy Heater photos) about his experience with the heater. He said:

       “I use mine in my camper out on the ice. I have fans that circulate the air constantly. When I cook, I open the roof vent to release moisture. My surfaces do get “tacky” when I first fire it up but that goes away once everything is warmed up. I have been using them for years and have never had a mold issue.”

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       1. Our family lives in a 40yr old camping trailer full time while we are building our house. We use the Mr Buddy propane heater (like the one pictured) exclusively to heat our trailer. We do not have that much trouble with moisture. The windows get foggy, and some of the cabinet interiors can form condensation, so we have to be careful there. But, we live in Nevada, so the ambient humidity is usually pretty low, even in wet weather, and our trailer being so old, means that there is air leakage in just about every single window. I guess that’s a blessing and a curse. We do not let the heater burn while we are asleep (yes, it’s pretty darn cold by the time we wake up in the morning), or when we are not home. We also place large, homemade desicant packs in some of the areas that tend to collect the most moisture. The first winter we lived in here, we dealt with a lot of condensation. But we’ve learned a few tricks and last winter wasn’t nearly as bad. We’ll see if we can mitigate it even more this winter (hopefully our last on in the trailer!)

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          1. Glad to hear its working for you. You are correct about Nevada humidity. FYI: Some people have created brick heat sinks (thermal mass) around the Mr Buddy. Basically laying brick/stone/tile under the unit to the sides and back. The bricks absorb the heat when the unit is running and then release the heat later. It might be a bit putzy but something to consider so there is a bit of radiant heat overnight. You could use these type of bricks or go to your local home improvement store and get bricks or more decorative tile to cover bricks (creating more thermal mass). If using stone stick to basalt, granite, and gneiss (less chance of it exploding at very high temp). Making a 4 sided box (left, right, back and bottom) allows the most thermal storage and would be most simple to create. If its in a corner just do 3 sides. The more mass you can squeeze in the better. All the best.

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    2. Good point about the water vapor from a propane heater. To handle it, just set up a few moisture absorbers in the room.

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