The TOTO S5 is the Washlet I’d buy for most people in 2026, because it fixes the short warm-water supply that sank the C5, adds four user presets and a night light, and comes in a round size the K300 never offered. The K300 still earns a spot if you have an elongated toilet and find it priced below the S5, since it’s the seat I tested for months and it never let me down.
I’m Dave, the Home Improvement Dude. I installed and tested both the TOTO C5 and the K300 extensively, and the K300 won that matchup without much drama.
Then TOTO discontinued the C5 and replaced it with the Washlet S5. I haven’t tested the S5 yet, so everything I say about it comes from TOTO’s spec sheet, clearly labeled. Where the S5 keeps a trait I measured on the C5, I’ll tell you that finding is carried over.
TOTO S5 vs K300: Quick Summary Table
The two seats are closer than any TOTO Washlet comparison I’ve written before, and the differences mostly come down to fit, presets, and price.
| Feature | TOTO S5 | TOTO K300 |
|---|---|---|
| Price at Bidet King | About $668 to $780 | About $699 (SW3036), $725 (SW3036R) |
| Warm water | Continuous (instant heater) | Endless (instant heater, tested) |
| User presets | 4 | 2 |
| Night light | Yes | No |
| Bowl sizes | Elongated and round | Elongated only |
| Warranty | 1 year | Check the SKU’s paperwork |
Both are electronic bidet toilet seats with a heated seat, warm air dryer, deodorizer, PREMIST bowl spray, and a wireless remote. If you came here wondering which TOTO bidet seat has the stronger core wash, the spray specs are nearly identical, so the decision lives elsewhere.
Why This Comparison Changed
My old verdict rested on one big flaw in the C5, and the S5 removed that flaw. The S5 swaps the C5’s small tank for an instantaneous heater and keeps the remote-driven layout people liked, which shrinks the gap between it and the K300 to a handful of convenience features and a few dollars.
What Changed When the S5 Replaced the C5?
The C5 was TOTO’s best-selling remote Washlet for years. In my testing, its weak spot was obvious: a small heated tank that started above 100°F and ran cool around the 40-second mark. You got roughly 40 seconds of warm water, then it had to refill and reheat.
The S5 replaced the C5 in TOTO’s 2025 refresh of its Washlet models. According to TOTO’s spec sheet, the S5 uses an instantaneous heater that supplies continuous warm water. That’s the single biggest change, and it’s the reason this article exists.
TOTO’s spec sheet also lists a few additions over the C5 I tested:
- Four user presets on the remote
- A night light
- EWATER+ wand cleaning
- CLEAN RESIN surfaces and a seamless seat design
- A docking station for the remote
The rest of the experience (heated seat, warm air dryer, deodorizer, SoftClose lid) carries over from the C5 lineage. You can still read my full TOTO C5 Washlet review to see how that older seat performed.
Why My Earlier K300 Verdict Needs a Fresh Look
In my original TOTO C5 vs K300 comparison, the K300 was the better bidet. Prices were similar, but the K300 had endless warm water from a tankless heater, used less power, and sat lower on the toilet.
I even described the K300 as closer to TOTO’s luxury S500e than to the C5. That was a big compliment for a mid-priced seat.
The S5 knocks out the main reasons I picked the K300. Warm water and heater efficiency no longer separate these two. What’s left is a list of smaller trade-offs: preset count, the night light, bowl shape, and street price.
It’s also worth knowing TOTO has discontinued the K300 and replaced it with the KS6. You can still find K300 stock, but you’re buying a model at the end of its run.
Warm Water: No Longer the Deciding Factor
Both seats now heat water on demand, so neither one runs cold mid-wash. That used to be the whole fight. In 2026, instant warm water is the baseline for any TOTO remote seat worth buying.
What My C5 and K300 Tests Showed
On the K300, warm water never ran out in my testing. You get Off (cold) plus three settings from 95°F to 104°F, and the instantaneous heater holds the chosen temperature as long as the wash runs.
The C5 was a different story. Its tank started above 100°F, then cooled noticeably around 40 seconds in. For quick front washes that was fine. For a longer rear wash, you felt the drop.
That 40-second limit was the most common complaint I heard from C5 owners, and it’s the exact problem I cover in my guide to a bidet water that’s too cold. The K300 solved it, which is why it won.
What the S5 Spec Sheet Says About Continuous Warm Water
TOTO’s S5 spec sheet lists an instantaneous heater with continuous warm water. The temperature range is 95°F to 104°F, the same window as the K300 I tested.
I haven’t measured the S5’s water temperature myself, so I won’t give you a number for how fast it heats or how steady it stays. On paper, though, it uses the same type of heater and the same temperature range as the K300.
That puts the two seats on equal footing for warm water. If continuous warm water is your top priority, either one delivers it according to TOTO, and you can read more about why it matters in my warm water bidet guide.
Cleansing Spray and Nozzle
The wash itself is close to a tie: the S5’s published spray flow overlaps almost exactly with what I measured on the K300, and both use TOTO’s self-cleaning wand with PREMIST. The bigger question is which K300 version you buy, because only one of them gets EWATER+.
How Do the Front and Rear Wash Specs Compare?
Here are the published and tested flow numbers side by side:
- S5 rear wash (spec sheet): 0.07 to 0.11 gal/min
- S5 front wash (spec sheet): 0.08 to 0.11 gal/min
- K300 (my testing): 0.07 to 0.11 gal/min (0.27 to 0.43 L/min), five pressure settings
When I tested the C5 and K300, both aerated at about 0.11 gal/min (0.43 L/min) on high. The S5 tops out at the same 0.11 gal/min on paper, so I’d expect similar coverage, though I haven’t run my spray tests on it.
On the K300, the wash felt gentle but thorough. It uses far less water than cheap seats spraying around 1 L/min and still cleaned as well in my test. Oscillation made the biggest difference; I got the best coverage by turning it on and nudging the nozzle position during the wash.
The K300 I tested had no separate wide front cleansing button, and the regular front wash on low was soft enough for my household. TOTO’s comparison chart lists wide front cleanse across its lineup, so check the remote layout on the exact S5 you’re eyeing if that mode is important to you.
Which Versions Include EWATER+ Wand Cleaning?
EWATER+ is TOTO’s electrolyzed water system that sanitizes the wand after use. The S5 includes EWATER+ according to TOTO’s spec sheet, along with PREMIST, which mists the bowl before you sit so waste sticks less.
The K300 comes in two versions:
- SW3036R: includes EWATER+ (the newer version, about $725)
- SW3036: the older version without EWATER+ (about $699)
The K300 I recommend is the SW3036R. Both versions have the self-cleaning wand and PREMIST, but EWATER+ adds a sanitizing step for about $26 more. If wand hygiene is high on your list, my roundup of the best self-cleaning bidets explains how these systems differ, and my complete guide to cleaning a bidet covers the manual cleaning you’ll still do.
Dryer, Deodorizer and Heated Seat
Comfort features are a near-match, and the S5 publishes slightly more detail than I had for the C5. My K300 and C5 dryers tied in testing, and the S5’s dryer specs suggest the same class of airflow.
What I Found When Testing the K300 and C5 Dryers
The warm air dryers on the C5 and K300 tied in my testing. Neither replaced toilet paper completely, but both cut down on how much I used.
One behavior stood out on both seats. About 10 seconds after you stand up, a power mode on the deodorizer kicks on and runs for about one minute. It’s a small touch that helps in a shared bathroom.
The K300 uses an active carbon filter for the deodorizer. The heated seat on both worked as expected, with three temperature settings that warmed the seat evenly. If drying is a priority, my list of the best bidets that have dryers compares stronger options.
What Comfort Features Does the S5 Specify?
Here’s what TOTO’s S5 spec sheet lists:
- Warm air dryer: 95°F to 140°F, three settings, 8.83 cfm airflow
- Heated seat: 82°F to 97°F
- Deodorizer: included
- SoftClose seat and lid: included
The C5’s dryer and deodorizer behavior carries over to the S5 in TOTO’s documentation, so I’d expect the same post-wash deodorizer routine. That’s a carried-over observation from my C5 testing, not something I’ve confirmed on an S5.
I don’t have a published airflow number for the K300 to compare against the S5’s 8.83 cfm. In practice, my test showed TOTO dryers in this tier perform about the same, so I wouldn’t pick either seat for the dryer alone.
Remote, Presets and Convenience Features
The S5 wins this category on paper with four user presets and a built-in night light. The K300 remote is excellent, but it stores two presets and has no night light, and its lid situation needs clearing up.
Four S5 Presets vs. the K300 Remote
The K300’s wireless remote is one of the best I’ve handled. It’s double-sided, solid in the hand, and has illuminated buttons. It stores two user presets, which covered my household fine.
According to TOTO’s spec sheet, the S5 remote stores four user presets and sits in a docking station. For a family of three or four, that means everyone saves their own water temperature, pressure, and nozzle position.
The S5 also lists a night light. The K300 I tested had none. For seniors or anyone making nighttime trips, that’s a practical difference you’ll notice every night.
Neither seat offers auto flush on its own. That feature belongs to TOTO’s top tier, like the Washlet S7A, when paired with a compatible Washlet+ toilet.
Does the K300 Really Have an Automatic Lid?
I can’t confirm the K300 has an automatic open lid, so don’t buy it for that feature. The documentation disagrees with itself.
TOTO’s comparison chart marks “Automatic Open and Close Lid” across nearly every model, including the S7. TOTO sells the S7 as the S7A without the motorized lid, so I don’t treat that chart line as reliable. My own spec table from testing the TOTO K300 Washlet lists no auto open/close seat and lid.
What the K300 does have is a slow-close seat and lid plus easy removal for cleaning. If a motorized lid is a must, the S7A is the TOTO seat built around it.
Design, Fit and Sizes
The S5 fits more bathrooms because it comes in both round and elongated. The K300 is elongated only, which rules it out for a big share of older homes.
Will an S5 Fit a Round Toilet?
Yes. TOTO lists the S5 in both elongated and round versions. That’s the biggest practical advantage it has over the K300.
The K300 was never offered in a round size. When readers with round bowls asked me about it, I had to point them to other seats, as in my TOTO K300 vs S300e comparison.
TOTO’s fit chart also calls for at least 2 inches from the front face of the tank to the center of the mounting holes for the S5. Measure that before ordering, along with your outlet distance, since the S5 cord is 3.93 feet long.
On looks, the K300 is about 5 inches high in the rear and has a clean, low profile. TOTO says the S5 is 19% slimmer than the C5 and uses a seamless seat with CLEAN RESIN, which is easier to wipe down than seats with visible seams. I haven’t held the S5 next to my K300, so I won’t call a winner on bulk.
Check the Exact SKU Before You Buy
Both seats come in multiple versions, and some are meant only for TOTO Washlet+ toilets. Buying the wrong one is the most common mistake I see.
Here’s what to check:
- K300 with EWATER+: SW3036R (white #01 or Sedona Beige #12)
- Plain K300: SW3036 (white #01 or Sedona Beige #12)
- S5: confirm elongated vs. round, and confirm whether the listing is a standard seat or a Washlet+ version
On TOTO’s chart, the S5 appears as SW3446#01 and SW3445#01, with Sedona Beige listed for only one of them. Match the SKU to your toilet before you pay.
Energy Use
Both seats use instantaneous water heating, so the efficiency gap I found between the C5 and K300 no longer applies here. The C5 kept a tank of water warm around the clock. Tankless heaters only draw heavy power while you’re washing.
On the K300, my testing put monthly use at about 18 to 36 kWh, roughly $2 to $5 a month with the heated seat turned off. It also offers four eco power-saving modes, including Smart Saver, which learns when you use the bathroom.
The S5 spec sheet lists a 1,271 W rating. That’s a peak draw while heating, not a monthly cost. I haven’t metered an S5, so I won’t guess at its monthly kWh.
What I can tell you is that the heated seat drives most of the ongoing cost on any electronic bidet toilet seat. If you want to keep bills low on either one, lower the seat temperature or use the power-saving mode, and you’ll see the biggest change.
Price and Warranty
Pricing is tight enough that the cheapest listing on the day you shop decides more than the spec sheet does. Bidet King lists both seats within about $100 of each other, and TOTO publishes a one-year warranty for the S5.
What Do the S5 and Both K300 Versions Cost?
Here’s what Bidet King lists:
- TOTO Washlet S5: about $668 to $780, depending on size and color
- TOTO K300 SW3036 (no EWATER+): about $699
- TOTO K300 SW3036R (EWATER+): about $725
TOTO’s MSRP for the S5 in Cotton White is $932, and $674 for the K300, so the K300 has the lower list price while street prices land close together. The low end of the S5 range undercuts the K300 with EWATER+.
Since the K300 is discontinued, prices on leftover stock can swing. If a retailer drops the SW3036R well below the S5, the math changes. If both sit around $700, the S5 gives you more for the same money.
How Do the Warranties Compare?
TOTO lists a one-year warranty for the S5. That’s standard across TOTO’s mid-range Washlets in the current lineup.
For the K300, read the warranty terms on the specific listing and box. Leftover stock sometimes ships with different coverage terms depending on the seller, so confirm the term before you buy.
In my experience, TOTO seats hold up well. My K300 ran without issues through my testing period, which makes me comfortable with a one-year term on either seat.
Which Should You Buy?
For most buyers, the S5 is my pick, with the K300 as the better deal only when it’s clearly cheaper and you have an elongated bowl. A few other TOTO models also fit specific budgets better than either one.
Choose the S5 for a Round Fit or More Presets
Pick the S5 if any of these describe you:
- You have a round toilet
- Three or more people will use the seat and want their own settings
- You make nighttime bathroom trips and want a built-in night light
- You want the current model with full parts and support going forward
The S5 keeps everything I liked about the C5’s remote setup and adds the endless warm water I always wanted from it. On paper, it’s the C5 I would’ve recommended.
Choose the K300 When Its Price and Proven Performance Win
Pick the K300 if you have an elongated toilet and find the SW3036R noticeably below the S5. I’ve tested it, and it delivered endless warm water, a strong efficient wash, and a top-tier dryer.
Two presets cover a couple or a single user without trouble. Get the SW3036R with EWATER+ unless the plain SW3036 is a lot cheaper. You can see my full results in my TOTO K300 review.
When Is a Different TOTO Model Worth Considering?
A few other models fit specific buyers better:
- TOTO KS6: the K300’s replacement. Retailer listings describe it as nearly an S5 under the lid (four presets, EWATER+, night light) at around $500, elongated and Cotton White only. In a TOTO S5 vs KS6 matchup for elongated bowls, the KS6 often wins on price. In TOTO KS5 vs KS6 searches, note that the KS6 is the current model.
- TOTO S2: around $349, with continuous warm water and EWATER+ but a side control panel. In TOTO S2 vs S5, you pay roughly $300 more for the S5’s remote and presets.
- TOTO S7 and S7A: TOTO’s flagships, about $1,099 and $1,140 at street prices. In TOTO S7 vs S7A, the main difference is the S7A Washlet’s motorized auto open and close lid.
- TOTO S550e: discontinued. My TOTO S550e vs C5 comparison still helps if you find one on clearance.
TOTO S5 vs K300: Conclusion
The TOTO S5 is my pick for most people because it matches the K300 on warm water and spray specs while adding four presets, a night light, and a round option. The TOTO K300 remains a proven seat from my own testing, and the SW3036R is worth buying when it’s clearly cheaper and your toilet is elongated.
Bidet King is where I’d buy either seat, listing the S5 at about $668 to $780 and the K300 at about $699 to $725. Before ordering, measure your bowl shape and confirm the exact SKU, especially whether it’s a standard seat or a Washlet+ version.
Ready to buy? Bidet King sells every seat in this comparison. You can check current prices on the TOTO Washlet S5 here (affiliate link).