# Solar window heater?



## Belfrybat (Feb 21, 2003)

Feels strange to ask this question since it's supposed to be 101-104 the next week, but I'm trying to plan ahead. Heating costs (electric central) were horrendous last winter. Does anyone have any experience with solar window heaters similar to this one I found on e-bay?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260630072615&ssPageName=STRK:MEWAX:IT

I know there are ones that also attach to the outside of the house and are vented into the house, but they are much more expensive -- over $1000.00, plus I would need to pay someone to install one. This house has 5 windows facing SW, so wondered about getting a couple of these puppies to boost heat. Any ideas/ comments/ critics would be most welcome.


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## Roadking (Oct 8, 2009)

If you are handy, you can use the plans offered here... http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#ActiveAir for free... 
Ihave built several (similar to the Mother Earth ones), and they work very well on a south facing window, however, they are not really pleasing to the eye, but they are pleasing to the pocket...
Simply add a computer fan (uses abot 12v), and attach two, in parallel, battery maintenacne solar chargers from harborfreight.com, and viola...heat for the cost of materials.
Matt


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## Belfrybat (Feb 21, 2003)

So are you saying the kind that sits in windows don't work? I can buy two or three of the pre-made ones for the cost of paying someone to build one, plus materials.


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## Harry Chickpea (Dec 19, 2008)

If it sits inside the window, it can only give you marginal gains over just opening the blinds on the window. There is only a certain amount of heat available per square foot. If a unit hangs outside of a window, then it adds to the area.

Solar heat that isn't stored somehow is pretty useless in reducing heating costs. The amount of sun in the winter is less, and even on sunny bitterly cold days, many houses will not need very much additional heat. Night is a totally different story.


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## wy_white_wolf (Oct 14, 2004)

If it sits on the inside of the window you will see ZERO heat gain. All the solar power it recieves is already in your house.


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## SolarGary (Sep 8, 2005)

I totally agree with WWW -- these solar collectors that fit right over a window will not gain any more heat than the window itself does -- possibly less. With a regular window, nearly 100% of the sun that shines into the window gets absorbed in the room -- you can't really do any better than that. 

If you search down this page:
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm
for "Solar Window Heater" -- there are half a dozen collectors like the Mother Earth News Heat Grabber that fit just outside of a window, and use the bottom of the window to transfer the heated air into the room. These do work and provide some space heating, and they can be used in conjunction with a window and removed for the summer if you like.

Of course, the larger the collector you can build, the more heat you get. A collector with 1 square meter (11 sqft) of area might produce about 8000 BTU or 2.3 KWH of heat on a sunny day.

If you are up for a somewhat bigger project, the same page has a lot of ideas for larger collectors that will get you more heat. 


Gary


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## Belfrybat (Feb 21, 2003)

OK -- thanks for the advice. I had hoped I might be able to get a cheap heat. Just window gain did not help a lot last year as it was warm right in front of the windows, but not 6' into the room. I thought perhaps the fans on these units might help. Guess I'm going to have to save up for an outside unit -- big bucks for those, but probably worth it in the long run from what I'm hearing from you guys.


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## SolarGary (Sep 8, 2005)

Hi,
If you are at all into building things, solar air heating collectors are very cheap to build -- as little as $2 a sqft.

The solar air heating collectors like the ones listed here:
http://www.altestore.com/store/Solar-Air-Heaters/Your-Solar-Home-Solarsheat-Products/c1054/
seem very high priced. 

Gary


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## Belfrybat (Feb 21, 2003)

Thanks, Solar Guy. Actually the first solar collector in your link was one I had looked at, but need to save $$ if I'm going to get it. 

I am SO NOT into building things. I don't have the tools, know-how, or inclination. And paying someone here $20.00 an hour would probably cost almost as much as buying one, since this would be a "strange" item to build and take lots of "pondering" for the handyman.


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## SolarGary (Sep 8, 2005)

Hi,
This really hurts for a solar guy to say, but I think you would likely be a lot better off taking the $1000+ that these commercial solar air heating collectors cost and instead spend it on paying someone to:

- Seal your house better (ie caulk)
- Seal your heating ducts with duct mastic and insulate them.
- Upgrade your insulation
- Buy some thermal shades for inside your windows.

In other words concentrate on conservation and efficiency because they will pay better return than commercial air heating collectors.

If your utility offers an audit service (as lots of them do), I'd start with that. Most of the audit programs are a great deal and cost the utility a lot more than what they charge you (if they charge anything).

Just an example of how a few small and cheap projects can add up:
http://www.builditsolar.com/References/Half/DirtCheap.htm
Some of the projects in the example are ones that may not make sense for you, but the point is most people will have a few simple easy projects they can get started with that will payback in no time at all -- just need to find them.

A 30 sqft solar air heating collector might produce about 8 KWH worth of free heat on a sunny day. If you get (say) 150 sunny days a winter, that's about 1200 KWH saving in heat energy a year for an investment of $1500ish. The 8 projects in the example above save about 9 times a much energy a year and it only costs about $400 to do them all.

Gary


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## wy_white_wolf (Oct 14, 2004)

I agree with SG. Do eveerything you can to conserve first. Your ROI will be faster. Then you can use the savings to build/buy the air panels.

WWW


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## Belfrybat (Feb 21, 2003)

Again, thanks all. This is a doublewide mobile home, very well insulated and "tight". I had inside storm windows installed, which will help with heat loss as well--it certainly is helping with A/C. I moved from a house with propane space heaters and a wonderfully efficient wood stove, so the sticker shock of central heat really got to me last winter. Interestingly, even in 100F temps central air is not costing as much as the heat did. 

I've bookmarked the sites you listed and will look into getting either a wall hung or under the window solar unit made. I appreciate your advice.


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