How much money can you save with a bidet?
You can save money by buying a bidet. I didn't believe this statement until I ran the numbers myself 5 minutes ago. With a bidet, the cost savings comes from the money you're not spending on toilet paper. Of course, there's a tradeoff. Operating a bidet costs money. Surprisingly, toilet paper is more expensive than the water an electricity needed to run a bidet.
We'll start with the fun part: the savings. According to Georgia Pacific, the average American uses about 157 rolls of toilet paper per year. I'm a bidet owner, and I tracked my toilet paper usage. I found I use about 45 rolls of toilet paper per year. (Before I had a bidet, I was a heavy toilet paper user! I'd use about 20 squares per wipe and wipe multiple times per visit to the toilet! So I think my usage after getting a bidet is not particularly low, and some people might use even less with a bidet.)
Based on my last purchase of toilet paper, toilet paper costs $0.91 per roll. Multiplying that out gives us an annual cost of $143 for the average American and $41 for me, the bidet user.
Now, we have to add up the costs of using a bidet. Bidet costs come in two forms: water and electricity. As we'll see, the majority of the cost of operating a bidet is electricity. However, "eco" modes on modern bidets make this less of an issue.
Bidets use about one eighth of a gallon of water per use. If we imagine a typical person uses their bidet twice a day, that adds up to about 91 gallons of water. Currently, a gallon of water costs about $0.029/gallon where I am. This adds up to an annual cost of about $2.65.
Bidets use electricity to heat their seats and the water. Some bidets heat their water in a tank, and some bidets heat their water on-demand. The bidets with tank systems are less efficient because they have to keep their water hot all day long. The tankless bidets only need to heat up water as it's needed, so they use much less energy.
Bidets draw large amounts of power when operating. I measured the power draw of my bidet, a Brondell Swash 1000, when it was in use with a Kill-a-Watt. The power draw was 500 W. That's less than a third of what most hairdryers use.
Bidets spend most of their time in standby and eco modes. In standby mode, the bidet is on and ready for immediate use. In eco mode, the temperature of the heated seat is reduced, and the water heating elements are turned off. My bidet enters standby mode immediately after use, and it enters eco mode 10 minutes later. I measured the power draw of my bidet when it was in standby and eco modes to be 65 W and 0 W, respectively. This means my bidet uses about the same power as a light bulb when in standby mode and almost no power at all when in eco mode.
We can estimate the energy used by a bidet as the sum of the energy used when in use and the energy used in standby mode. A typical session with a bidet lasts 2 minutes or less, and we can assume bidets are used twice a day. That gives us 4 minutes of active use and 20 minutes of standby use per day or 25 hours of active use per year and 122 hours of standby use per year. We can multiply those by the power draw in each mode to find the energy used in kWh. Once we know the energy used, it's straightforward to calculate the cost of that energy.
Adding this all up gets us the number we've been waiting for: the money saved per person using a bidet. Getting this number is easy. We take the amount of money saved by using less toilet paper, subtract the cost of additional water used by the bidet, and subtract the cost of the electricity used by the bidet.
For me, the most exciting part of this analysis is that this savings is per person! If you have two people using this bidet, you save twice as much money! (You actually save a little bit more than twice as much because you don't have to pay twice as much money for the electricity used by the bidet in standby mode when two people use it. If another person starts to use the bidet in the middle of a standby mode cycle, that cycle gets cut short.)
I paid $572 for my bidet three years ago. Since my wife and I both use it, we're saving about $192 per year. Over this three year period, we've saved around $4. That means our bidet has paid for itself in just three years! Every year after this, our bidet will practically be paying us to use it! That's amazing.
For me, I've always thought of bidets as luxury goods: most people don't have them, they're expensive, and you can easily live your life without ever seeing one. Because of all these reasons, I expected bidets to be expensive to own, but they're not! Bidets can save you money every time you use them. Who knew luxuries could be cheaper than the status quo?