Build Your Own Solar Window Heater for $10 – Save $45 a Month

This is my project for the weekend – to build a solar window heater (shown in the video below). It’s been a fairly mild winter here in Japan thus far and I have managed not to take out the space heater, but it’s been getting colder and it is just a matter of time. With heating costs far above what they are in the US, it pays to find ways to save on heating where ever possible.

Heating bills are going to wreck more than a few budgets this winter even in the US with the price of oil skyrocketing, so finding an easy way to save on heating is something that I assume most people are interested in. The video below shows how to create a solar window heater for about $10 – I tested the plastic container with black paper shown at the end of the video and could feel the heat, so I’m definitely interested in this project. That $45 a month estimated savings will be about $100 a month here.

Take a look and I think you’ll find the video interesting – especially for those that are looking to decrease their heating bills this winter:

Easy FREE Home Heat!

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17 Responses to Build Your Own Solar Window Heater for $10 – Save $45 a Month

  1. Peggie says:

    I am going to try this one! Thanks for sharing. We use propane to heat and it is expensive. While I am not fond of the looks of that in the window, I sure could use the savings.

  2. mike says:

    I’m unconvinced – the physics don’t add up on this one.

    In order to make a room warmer, this box would need to either increase the amount of energy entering the room, or decrease the amount leaving it. I don’t see how it can do either.

    Put another way, while a stream of hot air will come out of it, and that will warm the room, the box will cast a shadow which will cool the room. They will cancel each other out and there will be no net gain in room temperature.

    If you still don’t believe me, consider this: on a sunny day, closing the curtains help keep a room cool–even if they’re dark colored curtains. Whats different about this box that makes it behave different from the curtains?

  3. Joan.of.the.Arch says:

    I agree with Mike above. This device would need to be placed outside the house in a space through which light would not otherwise pass on its way to illuminate and warm the room. The box does not make more heat than comes into the room without it’s presence, does it?

    To get extra heat into the room, place the box outside -say- on the brick or siding. Build a channel for warm air to flow from the box through to the slightly opened window, which, of course, must be sealed all around any gapped spaces.

    None the less, this is a reminder to me to go and open my south facing windows for the day.

  4. Joan.of.the.Arch says:

    eh–I’d better open my curtains, not my windows!

  5. Pingback: DIY solar window heater

  6. Mel says:

    Oh my goodness! I am so excited about this idea. We have been searching the net for ideas for my childs alternative energy project. I can’t tell you how much I appreciate you taking the time to put this on the net. We are now excited about the project and also excited about using it in our own home. Did mike and joan of the Arch try it? The person from Maine said a similar one worked for her. Maybe they should build one and experiement first. I will let you know how it turns out! Thanks again!

  7. Prof Paul Matty says:

    mike and Joan.of.the.Arch

    What a bunch of hypocrites.
    It is obvious, by way of your blinkered comments you have not attempted this project nor have any knowledge of physics of thermal energy transfer.
    I have both.
    The improvements to our test room was a 10deg C (not F) increase in room temperature 14

  8. heatmiser says:

    I may not be a professor, but I did go to engineering school where they drummed into our heads the concept of conservation of energy. Mike and Joan.of.the.arch are correct. That cardboard box with pennies in it is not going to make more energy come into the window than was coming into it before. Whether the sun is heating your hardwood floor or those pennies makes no difference. The box is probably just collecting heat that would normally have just radiated away into the house. There is only so much sunlight that is going to fit in that window.

    By the way – I believe it is illegal to damage United States Currency in that fashion.

  9. YouDumbAsses says:

    you’ve all been had…

  10. Shadowtek says:

    The box works by channeling solar radiation into a usable form, such as heat. Thats why you need a conductive source, as in copper.


    “By the way – I believe it is illegal to damage United States Currency in that fashion.”

    Btw, I pay taxes, those pennies are mine to do with what I please.

  11. chasd60 says:

    It works because it is changing light energy into heat energy.

    Paint one white and one black and you will see the difference. The white will reflect the light energy and the black will absorb the IR spectrum and convert it to heat.

    The downfall to this concept is that you give up X amount of window space for X amount of heat. A better idea would be something like the sungrabber shown here

  12. karen says:

    Would this work with lowE newer windows? We are getting them, and wondered, as the sun heat doesn’t come through them much as traditional windows.

  13. Jennifer says:

    I tried this thing at home.While the air inside the box did indeed get quite warm-up to 120 deg F, it did not warm the room, nor did it give out any heat at all. Perhaps a slow-moving fan would help it circulate.I made the box out of insulation board, painted black, with a glass cover and a hole at the top and bottom.I had such high hopes for this simple device. Oh well…

  14. css1971 says:

    It works because black substances absorb all (most) light and convert it to heat. Most rooms are light specifically to reflect as much light as possible. For the sceptical engineers and physicists, go look up emissivity and/or albedo.


    1. The max you’ll get is about 800-900 Watts per square meter of collector. That’s just the limit of what the sun can provide. So you’ll probably need several of these things. Making them into internal shutters on all south facing windows might be worth it. A single device, it’d have to be a small room with a lot of sun.

    Curtains are usually designed to restrict air flow. They insulate windows, so even black curtains will be less efficient due to lack of air flow.

    2. Insulation is way more important. If you have single glazing you might as well not bother, the heat will just go right back out the window. Take a look at the thermal conductivity of glass between 5 Celcius (winter outside) and 20 Celcius. It’s huge, kiloWatts in most windows. Adding a sheet of Plexiglass/Perspex/acrylic to the window with a 2cm air gap can cut that to a tiny fraction.

  15. Ben says:

    Sorry Dudes – my PHD in physics brain calculates the value to be nearly zero – once the sun goes in the window, you already have most of it making heat. Unless you put something on the house siding to INCREASE the effective window surface that catches sun then you get no gain. Try another clear layer on front and hook it so air flows in and out through a window and you may have something! Best to use some insulating board to make the sides and back too.

    Biggest thing is – gotta mount it outdoors to increase the heat into the house!

  16. jim spagnola says:

    Here at our huge sustainability project we have several solar heat applications. I was looking to hear an elevator control room, roughly 600 cubic feet. I would have to agree that the surface area of the solar collector has to be greater than the window itself. A widow by itself is a solar heater, it just comes over a larger area. I can see how a commercial solar window heater may give the illusion of producing more heat by concentrating it via fans through a small area. This application may be great for better spot distribution of heat, but as others have said, unless you increase the solar energy capturing surface, there is no greater energy yielded by an interior mounted solar capturing device.

  17. Scott says:

    Use black felt – thick enough that you can’t see light through it while still allowing for good air penetration. This increases the solar energy capturing surface by magnitudes –

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