How to save on the heating bill AND stay warm – build a Kotatsu table!

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Brr… Winter is almost here. The overnight temperature plunged into the 30s a few times recently. 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 beautiful, 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 since 2003 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. The kotatsu table is our 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. You should turn it off when you’re done. I 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 through 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.

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 lived in a condo and we don’t have gas. The heating and cooling system ran on electricity which is more expensive than gas. Our monthly electric bill averaged around $60 in the warmer months and around $100 in the winter. We generally kept the temperature around 68 degrees with 2 space heaters and rely on our kotatsu table to warm up. Here is our energy usage from 2016 to 2018. *We moved into a house in 2019 and don’t have 2 years of record yet.

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.

What is a Kotatsu Table?

What is a kotatsu table exactly? A kotatsu table is basically a covered coffee table with a heating element underneath. It’s hard to describe the cozy comfort if you haven’t experienced it. Napping under the kotatsu table is heavenly. Trust me, it’s one of the best feelings in the winter.

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. Many Japanese homes are 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 more legroom. It is about 18” high. The 4 extra inches makes a huge difference.

This small kotatsu table at Amazon looks exactly like the one we first purchased. It’s not too expensive at $225. 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. (This item was $168 in 2018.)

Here is a nicer looking kotatsu table at Amazon for about $395. The height is still 14 inches, though. The tabletop is 36” x 20”. Unfortunately, that’s a bit too narrow for us. We need more space.

**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. It’s $50 from IKEA. The dimension is just about perfect – 46″x30″x18″. There is a smaller version that’s 35″x21″ as well. Alternatively, you could get 2 coffee tables from Amazon. Then, you’ll have two tops to use.

A 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. For example, a small space heater 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 $105. (The price increased quite a bit recently.)

$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 work too.
A 120 V to 100 V voltage transformer rated at 500W – You can get this transformer from Amazon for about $35. (*You need at least 500W.) North American outlets put out 120 V but Japanese appliances run on 100 V. The heating element will run a bit 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. If you crank up the setting, it could overheat. The transformer is nice insurance if you have curious kids around.
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 good alternative is to get some floor chairs from Amazon. Check it out. This looks pretty comfortable. However, this floor chair is not cheap at $50.

$10 power switch – Our heating element doesn’t have a switch so I got a power switch for it. It’s a lot easier to turn on and off than physically pulling the plug every time.
Corner braces – You can get these small corner braces from any hardware store. You probably should wait for the heating element to arrive so you’ll know what size to get.

Putting it together

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

Put the LACK coffee table together per IKEA’s instructions. Leave the lower shelf out for now.
Mount the heater. I screwed our heating element right into the bottom of the coffee table. You can attach it with 4 corner braces 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.
Throw the big blanket on top of the LACK coffee table.
Put the bottom shelf (or another tabletop) on top of the blanket.
Voila, you’ve got a kotatsu table!

If you can sit on the floor comfortably, you will love the kotatsu table. It is super comfortable and we don’t have to set our HVAC very high. We usually set the temperature at 70 degrees and that’s enough with the kotatsu table as a supplement. Our son really likes hanging out at the table as well. 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.

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.

Joe started Retire by 40 in 2010 to figure out how to retire early. After 16 years of investing and saving, he achieved financial independence and retired at 38.

Passive income is the key to early retirement. This year, Joe is investing in commercial real estate with CrowdStreet. They have many projects across the USA so check them out!

Joe also highly recommends Personal Capital for DIY investors. They have many useful tools that will help you reach financial independence.