TOTO Washlet C5 vs S7: Tank or Instant Heating?

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Short answer: the S7 uses an instantaneous water heater and offers 5 temperature settings for water, seat, and dryer, plus wide front cleansing and a night light; the C5 uses a small tank heater with 3 settings each. The trade-off is power: TOTO rates the S7 at 1290 W (1446 W max) versus 403 W (512 W max) for the C5.

How we compare: every spec in this article comes from official manufacturer specifications and manuals (starting with TOTO USA’s official product page), all listed under Sources below. We don’t run hands-on tests, and if a spec isn’t published, we say so. Last updated: October 2026.

I live in Japan, where both tank-type and instant-heating bidet seats are common. Instant heating is usually the feature people mean when they talk about a “step-up” model.

I haven’t installed either seat. Everything below comes from TOTO USA’s comparison chart, spec sheets, and manuals.

Quick Comparison Table

Feature	TOTO C5 (SW3084)	TOTO S7 (SW4726 / SW4724)
Shape	Elongated	Elongated
Controls	Wireless remote	Wireless remote (4-user memory)
Water heating	Tank (0.13 gal)	Instantaneous
Water temperature settings	3	5
Heated seat settings	3	5
Air dryer temperature settings	3	5
Water pressure settings	5	5
Wide front cleansing	No	Yes
Oscillating cleanse	Yes	Yes
Deodorizer	Yes	Yes
PREMIST	Yes	Yes
EWATER+	Yes (wand)	Yes (wand and bowl)
Night light	No	Yes
Energy-saver timer	6, 9 hours	6, 9 hours
Rated power	403 W	1290 W
Max power	512 W	1446 W
Auto flush capable	Not listed	Yes, with optional kit on select TOTO toilets
Annual energy use	Not listed	Not listed
Where to buy	TOTO C5 SW3084	TOTO S7 SW4726

Key differences at a glance

• Water heating: The C5 heats a small 0.13-gallon tank, while the S7 uses an instantaneous heater for continuous warm water.
• Temperature settings: The S7 offers 5 settings for water, seat, and air temperature, while the C5 offers 3 each.
• Extra features: The S7 adds wide front cleansing, a night light, EWATER+ for the bowl, and optional auto flush, which the C5 lacks.
• Power rating: The S7 is rated at 1290 W (1446 W max), while the C5 is rated at 403 W (512 W max).

The Differences That Matter

1. Tank vs instantaneous water heating

The C5 heats water in a small tank (0.13 gal per TOTO’s manual). The S7 spec sheet lists an “instantaneous water heater for continuous warm water and energy savings.”

TOTO doesn’t publish how long the C5’s warm water lasts or annual kWh for either seat, so I can’t quantify the difference in comfort or energy. What TOTO does say is that the S7 provides “continuous” warm water.

2. Finer settings

TOTO’s chart lists 5 settings for water temperature, seat temperature, and air temperature on the S7, versus 3 each on the C5. Water pressure has 5 settings on both.

3. Extra features on the S7

Wide front cleansing, a night light that “illuminates the side and the inside of the bowl,” EWATER+ for the bowl as well as the wand, a docking station, and auto flush capability with an optional kit on select TOTO toilets.

4. Power rating

The S7 is rated at 1290 W, with 1446 W max. The C5 is 403 W, with 512 W max. These are ratings, not daily use. The S7’s instantaneous heater draws high power only for short bursts, but TOTO publishes no annual figure to confirm actual use. I estimated the C5’s yearly cost in TOTO Washlet C5 power consumption.

Because of the higher rating, think about which outlet and circuit the seat will use. TOTO’s spec sheet lists a 3.9 ft cord for the S7 and recommends a surge protector.

Who Should Buy Which?

Choose the C5 if you:

• Want a remote, dryer, PREMIST, and EWATER+ at a lower rating (403 W)
• Are fine with 3 temperature settings
• Use the bidet for short washes

Choose the S7 if you:

• Want continuous warm water from an instantaneous heater
• Want finer 5-level temperature control
• Want wide front cleansing and a night light
• May add auto flush with a compatible TOTO toilet

If you want the S7 with a lid that opens by itself, see TOTO S7 vs S7A. If the C5 is already a stretch, compare it with the side-panel model in TOTO C2 vs C5.

Tank vs Instant: TOTO Japan’s Take

TOTO Japan explains the tank-type (貯湯式) vs instant (瞬間式) split the same way this comparison does: tank models keep warm water ready, instant models heat it on demand. TOTO adds one practical note: with instant models, in winter or when water is cold, the nozzle can take longer to come out after you press wash. The time can’t be changed, because it’s preparation time for heating. TOTO Japan’s top Washlet, the Apricot, uses instant heating. Japanese models differ from the US C5 and S7 and are built for 100 V.

One Japanese reviewer on Kakaku.com, upgrading from an older Washlet to an instant-heating Apricot F3A, noted a short wait before the spray starts but called it no real problem; others mention quiet operation. (Third-party reviews, not our own testing.)

Washlet C5 vs S7: Frequently Asked Questions

What is the main difference between the TOTO C5 and S7?

Water heating. The C5 uses a tank, and the S7 uses an instantaneous heater, per TOTO’s documents.

Does the S7 use more electricity?

Its rating is higher (1290 W vs 403 W). Annual kWh is not listed for either model, so actual yearly use isn’t confirmed.

Do both have a remote?

Yes. Both come with a wireless remote; the S7’s stores settings for up to 4 users.

Does the C5 have a night light?

A night light isn’t listed for the C5 on TOTO’s comparison chart.

Will both fit my toilet?

Both are elongated. Check TOTO’s fit requirements in which TOTO Washlet fits my toilet.

Is there a round S7?

TOTO lists the S7 as elongated only.

Related comparisons

• TOTO Washlet S7 vs S7A: Is the Auto Lid Worth It?
• TOTO Washlet C2 vs C5: What’s Actually Different?
• TOTO Washlet C5 Power Consumption: Watts and Yearly Cost
• Will a TOTO Washlet Fit My Toilet? Round vs Elongated

Sources

• TOTO USA, WASHLET Bidet Comparison Chart: https://www.totousa.com/washlet-new
• TOTO USA, C5 Instruction Manual (PDF; power and tank specs): https://www.totousa.com/filemanager_uploads/product_assets/OwnersManual/D07869_C5_Washlet_EN_IM.pdf
• TOTO USA, WASHLET S7 Elongated spec sheet SS-02227 (PDF): https://www.totousa.com/filemanager_uploads/product_assets/SpecSheet/SS-02227_SW4726(AT40)_SW4724(AT40).pdf
• TOTO USA, WASHLET Fit Chart (PDF): https://www.totousa.com/filemanager_uploads/product_assets/OwnersManual/Washlet-Fit-Chart.pdf
• TOTO Japan FAQ: instant vs tank-type Washlet (qa.toto.jp): https://qa.toto.jp/faq_detail.htm?id=161801
• TOTO Japan: Washlet Apricot product page (jp.toto.com): https://jp.toto.com/products/toilet/apricot/
• Kakaku.com: TOTO Apricot F3A reviews (Japanese): https://kakaku.com/item/J0000042092/
• Kakaku.com user reviews: TOTO Apricot F3 (Japanese): https://review.kakaku.com/review/J0000042091/

Specs checked October 2026. Prices and availability change, so check the current listing before buying.