Choosing between the TOTO S5 and K300 Washlet is one of the toughest calls you’ll face when upgrading your bathroom.
Both are excellent bidet seats from the world’s most trusted name in the category, but they’re built for different buyers — and this comparison will help you figure out which one is right for you.
| Feature | TOTO Washlet S5 (SW3446) | TOTO Washlet K300 (SW3036R) |
|---|---|---|
| Image |  |
 |
| Dimensions (L x W x H) | 21″ x 15.1″ x 5.5″ | 20.9″ x 15.1″ x 5.25″ |
| Water Heating | Instantaneous (endless warm water) | Instantaneous (endless warm water) |
| PREMIST | Yes | Yes |
| EWATER+ Wand Cleaning | Yes | Yes |
| Nightlight | Yes | No |
| User Memory Presets | 4 presets | 2 presets |
| Remote Control | Wireless handheld (wall-mount optional) | Illuminated wireless (handheld or wall-mount) |
| Buy Now |  |
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1. TOTO Washlet S5 Electronic Bidet Toilet Seat (SW3446#01)
The TOTO Washlet S5 is the brand-new successor to the popular — and now discontinued — TOTO Washlet C5, and it’s a significant upgrade in almost every way.
It brings instantaneous tankless water heating for truly endless warm water, a slimmer 19% reduced profile compared to its predecessor, and four user memory presets so every member of your household can save their own settings.
The S5 is currently a Wirecutter Top Pick for 2025, which says a lot about where it sits in the market right now.
Features
- Instantaneous water heating for continuous warm water with no waiting
- PREMIST sprays the bowl before each use to prevent waste from sticking
- EWATER+ electrolyzed water cleans the wand inside and out before and after each use
- Five spray settings for rear and front cleansing, with oscillating and pulsating modes
- Heated SoftClose seat with five temperature settings
- Warm air dryer with five temperature settings to reduce toilet paper use
- Built-in air deodorizer with powerful filters
- LED nightlight for nighttime visibility
- 4 user memory presets on the wireless remote
- CLEAN RESIN surface repels dirt and grime for easier cleaning
- Dimensions: 21″ x 15.1″ x 5.5″ (elongated only)
Pros
- Endless warm water — no tank to run out
- Slimmer, more modern profile than older TOTO C-series seats
- Four user presets — ideal for households with multiple users
- Nightlight is a genuinely useful feature you’ll appreciate every time
- 2025 Wirecutter Top Pick — best-in-class recognition
- CLEAN RESIN exterior makes routine cleaning much easier
Cons
- Only available in elongated size (no round option)
- Newer model, so long-term reliability track record is still building
- Slightly higher price point than the K300
If you want the most current, feature-rich TOTO bidet seat with a nightlight, four presets, and a slim modern design, the S5 is the clear choice.
If you’re looking for a broader overview of how it fits into the wider market, check out this bidet toilet seat comparison chart that covers top models side by side.
Check its current price on Amazon
2. TOTO Washlet K300 Electronic Bidet Toilet Seat (SW3036R#01)
The TOTO Washlet K300 has been one of TOTO’s most popular mid-range bidet seats since its release, and it’s still holding up as a strong contender in 2025.
It was TOTO’s first serious foray into the premium mid-range market — slimmer and more modern than the older C-series, yet more accessible than TOTO’s luxury S-series models.
The K300 packs in instantaneous water heating, PREMIST, EWATER+, a heated seat, a warm air dryer, and a deodorizer, all at a profile that’s just 5.25 inches tall at the rear — significantly slimmer than the old C200 or C100.
Features
- Instantaneous tankless water heating for continuous warm water
- Five spray settings for front and rear washing, with oscillating and pulsating modes
- PREMIST wets the bowl surface before each use to prevent waste adhesion
- EWATER+ self-cleans the wand inside and out before and after every use
- Heated SoftClose seat with adjustable temperature settings
- Warm air dryer with adjustable temperature
- Built-in air deodorizer with filters to neutralize bathroom odors
- Illuminated wireless remote — can be used handheld or wall-mounted
- 2 user memory presets
- Low-profile 5.25″ design — slimmer than older TOTO C-series seats
- Dimensions: 20.9″ x 15.1″ x 5.25″ (elongated only)
Pros
- Proven reliability — the K300 has been on the market and trusted by thousands of buyers
- Slimmest profile in TOTO’s mid-range lineup at 5.25″ rear height
- Illuminated remote control with wall-mount option is very convenient
- Instantaneous warm water — no cold start, no waiting
- Great value for a premium TOTO bidet seat
Cons
- Only 2 user memory presets vs 4 on the S5
- No nightlight — can be inconvenient for nighttime bathroom trips
- Elongated only — no round size option
If you’ve been comparing options like the TOTO C5 vs C200 and found yourself wanting something slimmer and more premium without going all the way to the S-series price point, the K300 is exactly that sweet spot.
Check its current price on Amazon
Head-to-Head: TOTO S5 vs K300 — Which Wins Each Category?
Water Heating Performance
Both the S5 and K300 use instantaneous (tankless) water heating, which means you get continuous warm water for as long as you need it — no tank to drain, no cold surprise mid-wash.
This is a major advantage both share over older TOTO models like the C100 or C200, which used tank-style heating that could run out.
For this category, it’s a tie — both deliver on demand, endless warm water.
**Winner: Tie**
Design and Profile
The K300 is actually slightly slimmer at 5.25″ rear height compared to the S5’s 5.5″.
However, the S5’s CLEAN RESIN surface and rounded corners make it easier to wipe down and keep clean on a daily basis.
If you want the absolute lowest profile, the K300 wins by a hair.
If you want a seat that’s easier to maintain and looks cleaner longer, the S5 has the edge.
**Winner: K300 (slimmest profile) / S5 (easier cleaning)**
Features and User Experience
This is where the S5 clearly pulls ahead.
The S5 adds a nightlight — something the K300 completely lacks — which is a genuinely appreciated feature if you use the bathroom at night.
The S5 also gives you four user memory presets versus only two on the K300, which matters in a household with multiple users.
If you want to read more about what makes heated bidet seats stand out, this rundown of the best heated bidet toilet seats puts it all in context.
**Winner: S5**
Value for Money
The K300 is typically priced lower than the S5, which makes it the better pick if budget is a real consideration for you.
You’re still getting instantaneous warm water, PREMIST, EWATER+, a heated seat, and a deodorizer — all the core premium features — just without the nightlight and with fewer presets.
For buyers on a tighter budget, the K300 offers excellent value.
**Winner: K300**
Hygiene Technology
Both seats are fully equipped with TOTO’s signature hygiene tech: PREMIST wets the bowl before each use, and EWATER+ automatically cleans the wand inside and out with electrolyzed water both before and after every use.
Neither seat requires you to manually clean the nozzle between uses — it handles that entirely on its own.
This is the same hygiene technology found across TOTO’s entire lineup, which is one reason the brand is so widely trusted.
**Winner: Tie**
Verdict: Which One Should You Buy?
**Buy the TOTO Washlet S5 if…**
You want the latest and most feature-complete TOTO bidet seat available today.
You use the bathroom at night and will appreciate the LED nightlight.
You share your bathroom with multiple people and need four customizable user presets.
You want a seat that’s easier to clean with its CLEAN RESIN surface and rounded corners.
You want the confidence of buying a 2025 Wirecutter Top Pick.
Check the TOTO Washlet S5 on Amazon
**Pick the TOTO Washlet K300 if…**
You want a proven, established TOTO premium bidet seat at a lower price point.
Two user memory presets are sufficient for your household.
You prefer the absolute slimmest possible profile at 5.25″ rear height.
You like the illuminated remote control with easy wall-mount capability.
You don’t care about a nightlight and want to save a bit on price.
Check the TOTO Washlet K300 on Amazon
For buyers who are still deciding whether a bidet seat is the right choice over a full bidet toilet combo, you might find this bidet toilet vs bidet seat comparison helpful before you finalize your decision.
FAQ
Is the TOTO C5 still available?
The TOTO Washlet C5 (SW3084) has been discontinued by TOTO. The official current replacement is the TOTO Washlet S5 (SW3446), which improves on the C5 with instantaneous warm water, a nightlight, four user presets, and a slimmer 19% reduced profile. If you were shopping for a C5, the S5 is the upgrade you want.
What is the difference between the TOTO S5 and K300?
The key differences are the nightlight (S5 has it, K300 does not), user presets (S5 has four, K300 has two), and the exterior surface (S5 uses CLEAN RESIN for easier cleaning). The K300 has a slightly slimmer profile at 5.25″ vs 5.5″ for the S5. Both share instantaneous warm water, PREMIST, and EWATER+.
Do I need a plumber to install either seat?
No — both the S5 and K300 are designed for straightforward DIY installation. They come with all necessary mounting and connection hardware. You do need a GFCI electrical outlet near your toilet. If there isn’t one already, a licensed electrician can install one quickly. For a broader look at installation-friendly options, see our guide to the best bidets for existing toilets.
Which TOTO Washlet is best for seniors?
Both the S5 and K300 work very well for seniors, as they both offer simple remote-controlled operation, heated seats, and warm air dryers that reduce the need for wiping. The S5’s nightlight is particularly useful for seniors who make nighttime trips to the bathroom. For a deeper look at senior-focused options, check our roundup of the best bidets for seniors.
Conclusion
Both the TOTO Washlet S5 and K300 are excellent bidet seats that deliver TOTO’s core premium experience: instantaneous warm water, PREMIST bowl protection, and EWATER+ wand hygiene.
The real question is whether the S5’s added features — the nightlight, four user presets, CLEAN RESIN surface, and status as TOTO’s current flagship mid-range model — are worth paying a bit more for you.
If you want the best TOTO bidet seat available right now without stepping into the S7 or Neorest territory, the S5 is the answer.
If you want a slightly lower price, a proven track record, and the slimmest possible profile, the K300 remains a rock-solid pick.
Either way, you’ll be getting one of the best bidet experiences on the market — and you can read through our best bidets for home use guide if you want to see how both of them stack up against the wider competition before you decide.
