Brr… Winter is here. The overnight temperature plunged into the 30s a few times last week. This seems a bit early to me. Usually, it doesn’t get this cold in Portland until December. The weather is strange this year. It’s been a lot drier than usual. The crisp sunny days are incredible, but this also means it’s colder. I’m not exactly sure how it works, but it isn’t as cold when we have some cloud cover or rain. It’s actually really great to have all these sunny days in October and November. I don’t think we’ve had a dry autumn like this in a long time. Anyway, it’s cold now and it’s time to convert our coffee table into a kotatsu table. Yes, I do this to save some money on the heating bill, but it is really cozy too.

Ahhh…. I love our kotatsu table. It’s so warm and toasty. We have been using our kotatsu table for over 15 years and it is still awesome! There is nothing better than warming up at the flick of a switch when you come in from the cold. Our kotatsu table is my favorite winter appliance, by far. It’s easy to DIY and it will pay for itself in the long run. I highly recommend investing a little time and building one for yourself.

*Disclaimer: You should not leave any heating device unattended. We haven’t had any problem, but everyone needs to be safe and pay close attention to your heaters. We take no responsibility for and will not be liable for anything you build. We may receive a referral fee if you purchase something from Amazon though the links in this post.

*This post was originally written in 2010. I update it every few years with the latest info. It’s much easier to buy a kotatsu table now that Amazon has grown so much.

How to build a kotatsu table

Staying warm AND save money

It’s about this time of year that all the personal finance magazines and blogs come out with articles on how to save money on heating. The usual advice to is to turn the thermostat way down and bundle up. This is good for the wallet, but it doesn’t work for us because Mrs. RB40, my wife, hates being cold. Luckily, I have a secret weapon. Our kotatsu table is the key to staying toasty and keeping our heating bill low.

We live in a condo and we don’t have gas. The heating and cooling system runs on electricity which is more expensive than gas. Our monthly electric bill averages around $60 in the warmer months and around $100 in the winter. We generally keep the temperature around 68 degrees with 2 space heaters and rely on our kotatsu table to warm up. Here is our last 2 years of energy usage.

electricity usage

The reason we were using the space heaters was because our HVAC stopped working in 2012. I just got a new system installed this spring because we plan to sell this condo soon. Apparently, the heat pump is more energy efficient than heater coil so our winter energy bill should be less this year. We’ll see if the bill is really lower as advertised.

If you’re looking for a space heater, you can’t go wrong with the DeLonghi oiled filled radiant heater. It worked great for us.

Oh, the new HVAC cost $6,600. That’s not cheap. I probably would’ve kept putting it off if we planned to stay here. The space heaters + kotatsu table worked well enough for us. Our condo is very well insulated. It hasn’t dropped below 70 degrees even with the overnight lows in the 30s. However, our condo will become colder as winter arrives with sustained low temperatures.

What is a Kotatsu Table?

What is a kotatsu table exactly? A kotatsu table is basically a covered coffee table with a heating element. It’s hard to describe the comfort level if you haven’t experienced it. Napping under the kotatsu table is heavenly. Trust me, it’s really nice.

I’m not sure where I first learned about the kotatsu table. I must have seen it in a Japanese manga or anime when I was a kid. The kotatsu table is very common there and every household has one. Most Japanese housing is not insulated well and the kotatsu table is an economical way to stay warm. Why heat the whole house? It’s much cheaper to heat your own personal space.

You could buy a kotatsu table on eBay or Amazon for $150-400, but that has some drawbacks. They used to have a high shipping cost because most kotatsu tables are shipped in from Japan. A few years ago, you could only find them on eBay. Now, you can get it on Amazon with free shipping! That’s awesome. It’s a lot more affordable now. However, there is still another problem.

One issue is that the kotatsu tables are generally pretty small. The usual tabletop size is 31×31 inches (80 cm) and most are only 14 inches high. This is too short if you’re tall. We purchased our first kotatsu table at a Japanese store in CA for about $130. After a few years, I decided to build a bigger and taller table because we wanted more space. Our DIY kotatsu table is a lot more comfortable now with the additional legroom. It is about 18” high. The 4 extra inches made a huge difference.

This small kotatsu table at Amazon looks exactly like the one we first purchased. It’s not too expensive at $168. The size is 30” x 30”. I’d go for this one if you don’t want to build your own. It’s a bit short though at 14” high.

small kotatsu table

Here is a nicer looking kotatsu table at Amazon for about $360. The height is still 14 inches, though. The table top is 36” x 20”. That’s a bit too narrow for me.

small kotatsu table

Build your own kotatsu table

What you need

  • A Coffee table – You need to find a coffee table with two top surfaces.  The LACK Coffee table from IKEA is perfect for this, $80 at Amazon. If you have a local IKEA store, I’d get it there. 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. That’s perfect for us. There are two sizes and I recommend the bigger one. The table top is a good size at 46” x 30”.

LACK coffee table kotatsu table DIY

  • kotatsu table heating elementA heating element – You can buy a “kotatsu heater” on Amazon or eBay. They used to charge $30 shipping in 2011, but now there are many free shipping options. 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 use and it’s less expensive now. I wouldn’t cheap out on this. Here is one on Amazon for $75.
  • $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.
  • voltage transformetA 120 V to 100 V voltage transformer – You can get this transformer from Amazon for less than $20. North America outlets put out 120 V but Japanese appliances run on 100 V. The heating element will run hot if you don’t use a step-down transformer. Currently, we don’t have a transformer and we only use the heater on the lowest setting. Now that this item is pretty cheap, I’m ordering one from Amazon. It’ll be easier to adjust the heating element and protect against overheating. I believe a transformer used to cost around $40, so I didn’t get one previously. The bonus here is the on/off switch. It’ll be useful because most heating elements don’t have a switch. You have to pull the plug to turn it off.
  • Optional: Pillows to sit on.  You can also pick up some big pillows from IKEA while you’re there. It’s a lot more comfortable than just sitting on the carpet. Another cool alternative is to get some floor chairs from Amazon. Check it out. This looks pretty comfortable. However, this floor chair is not cheap at $45.

floor chair

  • belkin power switch$10 Belkin power switch – Our heating element doesn’t have a switch so I got a Belkin power switch for it. It’s a lot easier to turn on and off than physically pulling the plug every time. I’d go with a transformer instead of a switch at this price point. It’s not much more.
  • Corner braces – You can get these from any hardware store.

Putting it together

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 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.kotatsu table DIY build
  3. Throw the big blanket on top of the LACK coffee table.
  4. Put the bottom shelf on top of the blanket.
  5. Voila, you’ve got a kotatsu table!

If you can sit on the floor comfortably, a kotatsu table will be the best heating appliance that you ever had. We rarely used our forced air heater even when it was working. Well, the HVAC is fixed now, so we’ll see how much electricity the heat pump uses this winter. We’ll probably keep it at 70 degrees and continue to use the kotatsu table often. Our son really likes hanging out there. Oh, a side benefit is that it forces the family to hang out in the same area. We’ll play plenty of board games this winter.

FYI, the climate in Portland is moderate and our 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 (over 10 years ago). The house was bigger and had more exposure to the elements. A kotatsu table should still work quite well in a colder climate. Japan is very cold compared to Portland.

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

More on how to stay warm! – 10 Unconventional Ways to Save Money on the Heating Bill.


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