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How to save on heating bill AND stay warm! Build a Kotatsu table

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I wrote this article in 2010 and I’m giving it a facelift. We have been using our kotatsu table for over 10 years and we love it! There is nothing better than getting warmed up at the flick of a switch when it’s cold and rainy outside. It’s definitely my favorite winter appliance. It’s easy to build and it will pay for itself in just a few months. I highly recommend investing a little time and build one for yourself.

Save on your heating bill - Build a Kotatsu table

It’s about this time of the year that all the personal finance magazines and blogs come out with articles on how to save money on heating. I will join the fray and reveal our secret to keeping our heating bill low AND staying warm. The usual advice to is to turn down the thermostat and bundle up. This is good for the wallet, but it doesn’t work for us because Mrs. RB40 hates being cold.

We live in a condo and the heating is done by electricity. Our monthly electric bill averages around $45 in the warmer months and about $75 in the winter. Our HVAC bit the dust a few years ago, but we haven’t fixed it yet. The system is so old, they don’t make parts for it anymore. So our winter heating is done by space heaters and our kotatsu table. I want to fix our HVAC, but it’s just easier to put it off. It will cost over $3,000 for a new system and we need to rearrange our bookcases (a huge job) to access the conduit. Someday, we’ll get it fixed, but we’ve been doing okay so it’s not a high priority.

Kotatsu Table

The kotatsu table, in particular, gets a lot of use in the winter. It’s amazingly comfortable and we spend a ton of time around it. What is a kotatsu table exactly? A kotatsu table is basically a coffee table with two top surfaces, a heating element, and a big blanket to keep the heat in. I’m not sure where I first learned about the kotatsu table. I must have seen it in a Japanese comic or cartoon when I was a kid. The kotatsu table is very common there and every household has one. Most Japanese housing are not insulated well and the kotatsu table is an inexpensive way to stay warm.

You could buy a kotatsu table on eBay for $150-300, but that has a few drawbacks. Most kotatsu tables are shipped from Japan so it could take a while to get here. The expensive shipping cost probably rules this out for most of us. Another issue is that the kotatsu tables are generally pretty small. The usual table top size is 31×31 inches (80 cm) and most are only 14 inches high. We purchased our first kotatsu table at a Japanese store in Costa Mesa for about $130. That’s a great option if you have a local store that carries it. After a few years, I decided to build a bigger and taller table because we needed more table space. Our kotatsu table is a lot more comfortable now with the additional legroom.

Build your own kotatsu table

Here is how to make a kotatsu table. This is much more affordable than shipping one from Japan.


kotatsu table

  • $45 or $33 Coffee table – You need to find a coffee table with two top surfaces.  A LACK Coffee table from IKEA is perfect for this. The bottom shelf can be easily moved to the top. You can get it in birch, white, or brown. The LACK is about 18” high and that’s just about perfect for us. There are two sizes
  • $40 A 120 V to 100 V step-down voltage transformer – You can get this from Amazon. North America outlets put out 120 V but Japanese appliances run on 100 V. The heater element will run hot if you don’t use a step-down transformer. We don’t have a transformer and we only use the heater on the lowest setting.
  • $60 to $100 heating  element – You can buy one a “kotatsu heater” on eBay. They used to charge $30 shipping in 2011, but now there are many free shipping sellers. I tried other heating alternatives, but they don’t work that well for this purpose. A small space heater, for example, seems dangerous. The kotatsu heater element is designed specifically for this and it’s not that expensive now. I wouldn’t cheap out on this one. We also tried the “cozy legs.” It didn’t heat up enough for us.
  • $0 old king size blanket/comforter – We have plenty of spare blankets so this didn’t cost us anything. I like the king size, but a queen would probably work too.
  • $? pillows to sit on.  You can pick up some big pillows from IKEA while you’re there. It’s a lot more comfortable than just sitting on the carpet.
  • $10 Belkin power switch – I put the plug on a power switch. This made it much easier to turn on and off. I don’t have to plug it in every time I want to turn the unit on. Our heating element has a variable knob, but no off switch.
  • $3 four-pack corner braces – You can get these from any hardware store.

Putting together the kotatsu table is really easy. You probably don’t even need instructions, but here they are anyway.

  1. Put the LACK coffee table together per IKEA’s instructions. Leave the lower shelf out for now.
  2. Mount the heater. I screwed our heating element right into the bottom of the coffee table. You probably can attach it with 4 corner braces from Home Depot as well. Or you can build a frame as pictured below. The mounting holes are on the side of the unit as you can see from the image.mount kotatsu heater
  3. Throw the big blanket on top of the LACK coffee table.
  4. Put the bottom shelf on top of the blanket.
  5. Plug it in and you’ve got a kotatsu table!

If you can sit on the floor comfortably, a kotatsu table will be the best heating device that you ever had. We rarely turned on our forced air heater even when it was working. We spend a lot of time under the kotatsu table every winter and it saves us a lot of money on our heating bills. FYI, our climate is temperate and the concrete condo retains the heat well so our indoor temperature hovers around 64 degrees Fahrenheit. When we lived in a house, our gas bill would be over $150/month in the winter. Of course, it was a bigger space and had more exposure to the elements. I’m sure it will still work quite well in colder climate. Japan is very cold compare to Portland.

Happy building! How do you keep your heating bill down?

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{ 51 comments… add one }

  • Jack Fuller November 7, 2011, 2:07 am

    Wow. A unique way of staying warm this winter.

    • retirebyforty November 8, 2011, 7:37 pm

      Heh heh, thanks. I was getting tired of the usual advice to turn down the thermostat.

  • Little House November 7, 2011, 6:54 am

    Those tables sound really great on a cold day. However, on the DIY version, how do you make sure the heater doesn’t catch the table on fire? I’m a stickler about fire safety (my step-dad was a fireman).

    • retirebyforty November 7, 2011, 10:04 am

      I try my best to not leave it on when I’m not using it. If your legs are next to the heater, you’d know when it gets too hot. From what I understand, the ceramic heater element is not supposed to catch fire, but the risk is always there with any electronic heater.

      • joedartjr September 22, 2013, 8:03 pm

        An authentic kotatsu heater does not heat up like a space heater, it wont light the wood on fire. But it is possible if the blanket isn’t flame retardant that if someone was to physically put it into the heater and hold it there it could catch on fire, but you would have to purposefully do it.

  • PKamp3 November 7, 2011, 7:41 am

    We have a sun-room (other areas of the country might call them three-season rooms) and it’s gotten pretty cold at night the last month or so. We were looking at a cheap way to heat it since if we leave the door open the thin walls will radiate all of our heat away, haha.

    How hot does a kotatsu get? Is it so hot I have to be careful what type of wood I purchase on the table? Think it would be good in a 14×15 sun-room with tile floors… or is it the space heater for us?

    • retirebyforty November 7, 2011, 10:07 am

      My heater element is pretty hot, but I don’t think it can reach wood’s combustion point. The LACK table is made of particle boards and I haven’t had any problem yet. I don’t know about sitting on tile floors. It doesn’t sound comfortable…

  • MoneyCone November 7, 2011, 8:11 am

    I remember reading that post last year! The Kotatsu table sounds fantastic!

  • Miss T @ Prairie Eco-Thrifter November 7, 2011, 8:29 am

    This looks really neat. Not only on a functional level but they look really nice in a room too. Plus I love the name. It just sounds warm and cozy. I might just have to look into one of these.

    • retirebyforty November 7, 2011, 10:08 am

      It’s quite expensive to import one from Japan. If you live in LA, there are some stores that sell a ready made one starting at $150 or so.

      • Miss T @ Prairie Eco-Thrifter November 8, 2011, 6:22 am

        Good to know. Thanks. Looks like I will need to import either way if I want one since I live in Canada.

      • Jarrod May 31, 2012, 6:14 pm

        I live in LA and would love to buy on for my fiance who lived in Japan for two years. Where can I buy them in LA for the $150?

        • retirebyforty May 31, 2012, 8:52 pm

          We got one from Murakai market. Not sure how much it cost now.

  • Jeff @ Sustainable life blog November 7, 2011, 12:46 pm

    That’s a really creative idea and I love DIY projects, but I may be too tall for this one!

  • Roshawn @ Watson Inc November 7, 2011, 5:42 pm

    It does look really nice. I intially had the same question as Little House though.

    I think it is always good to rethink conventional wisdom, and since your November heating bill was only $10 more than the summer, that’s speaks volumes.

  • Aloysa November 7, 2011, 6:34 pm

    I remember this article! It was great then, it is great now! I also remember thinking wow! Never even heard about this table. :)

  • SB @ One Cent At A Time November 7, 2011, 7:08 pm

    This is great. But nothing beats a thermostat and a one click heating :) Unless you are counting pennies

  • Kellen November 8, 2011, 6:44 am

    Sometimes it’s cozier to have a warm spot like this than to heat the whole house – like how nice it is to snuggle under blankets when it’s cold. If the whole house is heated, then most of that warm air is not being used, PLUS can make all the air in the house even drier than winter air usually is.

    Thanks for the tips on making your own!

    • retirebyforty November 8, 2011, 11:06 am

      In our old house, we warmed the bedroom at night with a space heater and use the kotatsu table in the living room. The room temp was around low 60s and it worked quite well.

  • Tushar@EverythingFinance November 8, 2011, 6:46 am

    This is a neat little tip. We all like to cozy up next to the fireplace. Now we can also cozy up to a coffee table :)

    • retirebyforty November 8, 2011, 11:06 am

      A coffee table is much nicer to cozy up to than a fireplace. There is a spot to put your coffee, magazines, and laptop. 😉

  • Melissa November 8, 2011, 7:35 pm

    I love these! My husband’s parents still live in Japan, and their house gets very cold. These were wonderful; the whole family sits around it!

  • 101 Centavos November 8, 2011, 7:56 pm

    I’m not much of a floor sitter, but I think for warm legs on a cold night, I could adapt.

    • retirebyforty November 9, 2011, 10:26 am

      I was already sitting on the floor playing video games and such so it was an easy adjustment for me. :)

  • Paula @ AffordAnything.org November 8, 2011, 9:27 pm

    That’s fantastic! It’s great to read an actual unique tip like this — not just the same ol’, same ‘ol. And I marvel at the Japanese; they have great design and efficiency.

    • retirebyforty November 9, 2011, 10:25 am

      We love our Kotatsu table. It’s the best spot to gather in the winter.

  • catawba county nc real estate November 10, 2011, 7:22 am

    Great idea! This is a great solution to staying warm in the winter without paying an expensive power bill. Thanks for sharing!

    • retirebyforty November 10, 2011, 12:58 pm

      It’s really great, we love it.

  • Hank November 10, 2011, 9:40 am

    This is a very interesting idea. I had never even heard of a kotatsu table before.

    • retirebyforty November 10, 2011, 12:59 pm

      It works very well and saved us a lot of money on the power bill.

  • Steve January 25, 2012, 2:30 pm

    How do you use the table? When you “spend a lot of time under the kotatsu table” are you literally under the table, like it’s a kid’s fort? Or do you just stick your legs under there? Does it provide warmth if you’re just sitting next to it, or if you’re sitting on a couch and maybe just putting your feet underneath?

    • retirebyforty January 25, 2012, 2:52 pm

      It’s best to sit on the floor and stick your legs under the table then pull the blanket over your waist. It works great and warm your whole lower body!
      You can sit on the couch and stick your feet underneath too, but it is not as warm then. Sitting next to it is no good.

  • Gerard June 21, 2013, 10:18 am

    I wonder if you could get the heat from a dog bed heater instead of the heater you show in the picture. They’re cheaper and they look like they don’t use much power, or overheat.

  • Mary March 25, 2014, 6:43 pm

    I think an electric heating blanket might work here too.

  • Suzanne December 10, 2014, 9:50 pm

    We don’t have a kotatsu but we do use yutampo (Japanese hot water bottle) to warm our beds here in Japan. Yutampo is far better for one’s health — than an electric blanket, for example. One winter we went skiing in the Japanese alps at Nagano and the Inn had kotatsu for each room but no heating. So we were forced to sleep under the kotatsu — a bit dangerous in my opinion due to fire potential and health reasons, however, it was preferable to freezing to death those nights!

    Our homes here have electric flooring but it is too expensive to use often and I object to it for health reasons, as with the electric blanket or electric heating pad for pets. Electric ‘hot carpets’ are also popular here, but again, I do not think it is wise to expose one’s body to electrical current all winter long.

    • retirebyforty December 11, 2014, 10:09 am

      The Yutampo is a great idea. I will keep a look out for it. Mrs. RB40 uses a heat pack thing she warms up in the microwave. That works pretty well too, but it doesn’t last long.

  • Ernie Zelinski November 9, 2015, 12:43 am

    “How do you keep your heating bill down?”

    I don’t do much except close the heat vents in the rooms downstairs that I don’t use and open the drapes fully when the sun is shining through by south windows. Having said that, if it gets too cool for me I turn the heat up. When I was younger, I used to turn down the heat at night so much that when I woke up in the morning it was so cold I could see my breath. Not so anymore. That’s craziness. I am too prosperous to that anymore.

    Coincidentally, for anyone interested, in the last five minutes I came across this article about 9 Sneaky Ways to Cut Down the Heat Bills in Your Home:


    • retirebyforty November 9, 2015, 10:02 am

      I’m glad it doesn’t get that cold around here. :) It’s amazing what we could handle when we were young. Thanks for the article. There are some easy tips there.

  • Khen Elazar November 9, 2015, 1:05 am

    I wouldn’t try to save money on the heating element. I would buy a reliable element. You can probably buy from Ebay and AliExpress cheap elements, but you should look for a higher standart elements.

  • Pennypincher November 9, 2015, 1:25 am

    I’m with Mrs. RB40 on always feeling cold. Best tips are-wear several layers around the house. Now thermal base layers (thermal underwear) is made from polar fleece. This fabric is made from plastic (soda bottles!) and is one of the warmest. A few layers of clothing makes a huge difference. Wear a hat from this fabric (or wool) around the house, who cares what you look like! And sox, especially w/a bit of wool, like 5-10% makes a huge difference.
    I read that thermal window covers are one of the most effective ways to keep heat in, cold out. You could switch them out in the summer months.
    Fleece and down comforters are on all chairs and the sofa for use. The dogs even have their own.
    My best find lately is a small heater, the size of a shoebox, for $10 from Walmart. It is not recommended for bathrooms, but I’m super careful w/it and that’s exactly where I use it! Heats up in seconds for when you step out of the bath or shower, instead of heating up the whole house. It’s also cool to the touch. As long as you follow the instructions in the manual, this little heater is fantastic. The polar fleece thermal base layers are from Walmart too. Save your hard earned cash for more important things-like tropical vacations!

  • Justin November 9, 2015, 6:43 am

    This would be perfect for Mrs. Root of Good. I like it cold but this thing could keep her (and the kids!) warm.

    I’d just be concerned about the kids knocking it over and starting a fire.

    • retirebyforty November 9, 2015, 10:14 am

      Once you attached the heating element to the coffee table, it’s pretty much impossible to knock it over. You should try it.

  • MIKE November 9, 2015, 7:52 am

    hi Joe:

    wow, your indoor temperature is 64 degrees. That is amazing your kid and wife are ok at that temperature. For me at 68 degrees I already feel cold. We usually set ours around 69 to 70. and I thought that was being really economical. But still my gas bill is around $300 or so in the worst of winter. I also live in Portland.

    I have learned that by bundling up with extra layers of clothing. I usually have about three layers. That does the trick for and it works better for me though.
    I don’t feel as cold, and I don’t need to set the heat so high.

    Just a suggestion…

    My family needs at least a minimum of 68. especially my mom when she comes over to visit.

    • retirebyforty November 9, 2015, 10:15 am

      That’s whey we spent so much time under the kotatsu table… Actually, I have been turning it up the last few years. The 64 degree was in 2010. I usually keep it at 68 now. :)

  • Stockbeard November 9, 2015, 12:06 pm

    “Most Japanese housing are not insulated well and the kotatsu table is an inexpensive way to stay warm.”

    This sums it up. Having lived in Japan for 9 years I can say that Japan is generally clueless about insulation, and the Kotatsu is the “poor man’s” answer to a bigger problem I’m pretty sure it’s inefficient if you look at the overall numbers, unless you like to have your house freezing cold except for a 1sq meter area. If you really have a problem with heat in your house, the real solution is to improve insulation and fix your central heating.

    A Kotatsu in itself is great, but good luck when you want to start working on your computer at your desk, because then you’ll be freezing.

    Our Electricity bill was twice as big in Japan as it is in the US, by the way ( http://howtoretireearly.net/a-comparison-of-the-cost-of-living-in-japan-and-the-us/ ). Terrible insulation does that to you.

    The kotatsu itself is a nice piece of appliance, but it’s sad that it is considered as the “right” solution to heating expenses, when it clearly is not.

    Great DIY post, nonetheless!

    • retirebyforty November 9, 2015, 10:00 pm

      You’re right. The real solution is to improve the insulation. Our building is very well insulated and we get radiant heat from the units around us. Thanks for the link. It’s interesting to see the cost of living comparison. I’d love to live in Japan for a while.

  • Jason Fieber November 9, 2015, 1:50 pm


    Interesting stuff. Never heard of it before, but that’s pretty unique. I know it can get pretty cool/wet there in Portland for more than half the year, so it’s awesome you guys found a way to reduce the heating expenses down somewhat.

    “Happy building! How do you keep your heating bill down?”

    My answer to that question is living in a tropical climate. Practically no heating bills here in Florida. Keeping the A/C near almost 80 year round means it’s pretty comfortable in the apartment with minimal HVAC expenses. I think we spent like $75 on electricity last month. Works for me. :)


    • retirebyforty November 9, 2015, 10:03 pm

      It’s cold in the winter, but not bad in the spring and fall. I think you would be able to handle it. The people with the most problem are stuck in the office from 9 to 5. It’s not so bad when you can be outside once in a while.
      I like your answer. I’m sure I’ll end up in a tropical zone eventually.

  • Matt November 9, 2015, 4:16 pm

    Looks like a great way to stay warm and to have the family all spend more time together huddled around the table!!

  • Lin November 13, 2015, 8:52 am

    Thanks for this great article! Though I am aiming to retire by 40 and really love the blog for the personal finance tips, I’m pretty sure this was the first article I read. I constructed a kotatsu and it has been fantastic! I’m not really sure whether it has saved us much money, as all three of my roommates tend to favor more heating than I do in winter. But I compromise a bit because they’re all awesome.

    When I lived in Japan, the kotatsu was wonderful as a center of family life. But yeah, the insulation was pretty terrible. It was amazing how warm and cuddly you could be, though, just by taking a super hot bath, having some kotatsu time, then snuggling up underneath a bunch of blankets. I am going back for a visit this winter and can’t wait!

  • kachun November 14, 2015, 7:34 pm

    I just bought a Kotatsu heater from Rakuten. The heater itself is ~$16 usd plus ~$35 shipping. The unit arrived in one week. It works fine. My house temperature is around 65 degree, but I feel very cozy under the table with my short. There is only one problem. The top part of the heater can get pretty hot. I may be completely wrong, but I think it’s better to leave some space between the heater and the table when you install it on a Ikea table.

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