If you’re torn between the Coway Bidetmega 400S and 500S, you’re not alone — both are impressive bidet seats, but the right choice depends on what you actually need.
In this guide, you’ll get a full head-to-head breakdown of the Bidetmega 400S vs 500S so you can make a confident, informed decision for your bathroom.
| Feature | Coway Bidetmega 400S | Coway Bidetmega 500S |
|---|---|---|
| Image |  |
|
| Dimensions (L x W x H) | 20.7″ x 5.3″ x 1.0″ | 20.9″ x 5.3″ x 1.0″ |
| Water Heating | Tankless / Instant | Tankless / Instant |
| Lid | Soft-close (manual) | Auto open/close |
| Deodorizer | No | Yes (activated carbon) |
| Nightlight | Yes | Yes |
| Triple Hygiene Care | Yes (WaterShield + UV + auto-clean nozzle) | Yes (WaterShield + UV + auto-clean nozzle) |
| i-wave Cleaning Tech | Yes | Yes |
| Buy Now |  |
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1. Coway Bidetmega 400S Electronic Bidet Toilet Seat
The Coway Bidetmega 400S is the brand’s signature mid-range model, and it delivers a feature-rich experience that punches well above most competitors in its class.
It’s the go-to pick for people who want cutting-edge hygiene technology and customizable comfort without spending top dollar — and if you’ve been browsing the bidet toilet seat comparison chart trying to make sense of the market, the 400S stands out as one of the most well-rounded options available.
Features
- Coway’s i-wave cleaning technology with 3-stage course wash and 1-stage general wash
- Tankless instant water heating for continuous warm water
- Triple Hygiene Care: WaterShield misting, auto-cleaning nozzle, UV nozzle sterilization
- Soft-close lid
- Heated seat with 4 temperature settings and overheat protection
- Adjustable warm air dryer with 4 temperature levels
- LED nightlight for easy nighttime use
- Wireless remote control (wall-mountable or tabletop dock)
- 2 user memory profiles (Profile 1 preset as child mode)
- Eco mode for energy savings
- IPX4 water-resistant rating
- Fits both elongated and round toilets
Pros
- Exceptional hygiene features at a more accessible price point
- Instant hot water — no cold surprise at the start of the wash
- UV nozzle sterilization is rare at this price
- Child-friendly profile built in — great for families
- Easy installation that fits most standard toilet shapes
Cons
- No built-in deodorizer
- Lid is soft-close but requires manual operation — no hands-free opening
- No auto-close lid function
Check its current price on Amazon
2. Coway Bidetmega 500S Electronic Bidet Toilet Seat
The Coway Bidetmega 500S is the premium step-up in the Bidetmega line, adding several quality-of-life upgrades over the 400S that make it feel genuinely luxurious to use every single day.
If you’ve been researching the best bidets for home use and keep finding yourself drawn to fully hands-free, touchless operation, the 500S is built exactly for you — it’s the kind of upgrade that turns a routine bathroom visit into something you actually look forward to.
Features
- All features of the 400S, plus:
- Auto open/close lid — fully hands-free entry and exit
- Activated carbon deodorizer for neutralizing odors
- Same i-wave cleaning technology with Move, Wide, and Air+ modes
- Triple Hygiene Care with WaterShield, UV nozzle cleaning, auto-cleaning nozzle
- Tankless instant water heating
- Heated seat with 4 temperature settings
- Warm air dryer with 4 temperature levels
- LED nightlight
- Wireless remote control (wall-mountable or docking station)
- 2 user memory profiles
- IPX4 water-resistant design
- Available in round and elongated
Pros
- Completely touchless experience — auto-open lid means zero contact with the seat
- Activated carbon deodorizer keeps the bathroom fresh automatically
- All the same advanced cleaning power as the 400S
- Ideal for households with seniors or users with limited mobility — check out our guide on best bidets for seniors for more context
- Sleek, high-end feel that matches premium bathroom aesthetics
Cons
- Auto-close lid resets after UV cleaning cycle (every 12 uses or 36 hours), requiring you to toggle it off manually if preferred off
- Higher price point than the 400S
- Deodorizer and auto-lid may feel unnecessary for minimalist buyers
Check its current price on Amazon
Cleaning Performance: 400S vs 500S
Both the 400S and 500S share the same core i-wave cleaning engine — and that’s a good thing, because it’s genuinely impressive.
The system delivers a multi-stage wash with three modes: a thorough 3-stage course wash, a consistent 1-stage general wash, and special function buttons including Move (nozzle repositioning), Wide (broader spray), and Air+ (bubble-infused stream for a gentler touch).
The Triple Hygiene Care system — which combines WaterShield misting, UV nozzle sterilization, and auto-cleaning before and after each use — is identical across both models.
If powerful, hygienic cleaning is your top priority, neither model has an edge over the other here.
Winner: Tie. Both deliver the same excellent cleaning technology.
Hygiene and Odor Control: 400S vs 500S
This is where the 500S pulls meaningfully ahead.
The 500S adds an activated carbon deodorizer that automatically filters out bathroom odors — a feature completely absent on the 400S.
If you share a bathroom with others, live in a smaller space, or simply care about keeping things fresh without spraying air freshener, this matters a lot.
The 400S still has the WaterShield mist to reduce bowl contamination, but there’s no odor filtration built in.
For anyone browsing our list of best bidets with dryers, note that both models include warm air dryers — the deodorizer on the 500S is a separate, bonus upgrade.
Winner: Coway Bidetmega 500S. The deodorizer is a meaningful real-world upgrade.
Comfort and Convenience: 400S vs 500S
Day-to-day, the most noticeable difference between these two models is the auto open/close lid on the 500S.
On the 400S, the soft-close lid means it won’t slam, but you still need to lift it manually before sitting down.
On the 500S, the lid opens as you approach and closes automatically after you’re done — a touchless experience from start to finish that genuinely changes how the bathroom feels to use.
Both seats have a heated seat with 4 temperature levels, an adjustable warm air dryer, and a soft nightlight — so comfort features are well-matched across both models.
Users with limited mobility, arthritis, or those who just love a truly hands-free experience will appreciate the 500S auto-lid significantly more — something worth considering if you’re reading our guide on bidets for seniors.
Winner: Coway Bidetmega 500S. The auto-lid is a comfort game-changer for daily use.
Installation and Compatibility: 400S vs 500S
Both the 400S and 500S are designed for straightforward DIY installation and are available in both elongated and round versions, meaning they’ll fit the vast majority of standard American toilets.
Installation takes most people under 30 minutes — just remove your old seat, attach the mounting bracket, slide the bidet into place, and connect the water supply.
Both models require a standard electrical outlet nearby, so make sure your bathroom has one within reach before ordering.
If you’re not sure whether a bidet seat will fit your toilet, our breakdown of best bidets for existing toilets covers compatibility in detail.
Winner: Tie. Both are equally easy to install and compatible with the same toilet types.
Value: 400S vs 500S
The 400S is the better value pick if you want the Bidetmega cleaning experience without the premium extras.
The 500S costs more, but what you’re paying for — auto-close lid, activated carbon deodorizer — are genuine real-world upgrades, not just marketing fluff.
For budget-conscious buyers who still want a high-quality electric bidet, the 400S delivers most of what the 500S does at a lower cost.
If you’re still exploring price ranges, our roundup of best bidets under $500 also has strong options worth considering.
Winner: Coway Bidetmega 400S for value; 500S for those who want every convenience feature included.
Verdict — Which One Should You Buy?
Both the Bidetmega 400S and 500S are excellent bidet seats built on the same strong foundation.
The real question is how much you value hands-free convenience and odor control.
Buy the Coway Bidetmega 400S if…
- You want the full Bidetmega cleaning experience at a lower price
- You don’t mind lifting the lid manually
- Odor control isn’t a priority in your bathroom
- You’re upgrading from a basic bidet and want a significant step up — see our comparison in the bidet toilet seat comparison chart
Buy the Coway Bidetmega 500S if…
- You want a completely touchless bathroom experience
- An activated carbon deodorizer matters for your household
- You share the bathroom with seniors or users who benefit from auto-lid operation
- You want the most premium version of the Bidetmega line without compromise
FAQ
Is the Coway Bidetmega 400S worth it over cheaper bidet seats?
Yes. The 400S includes features like UV nozzle sterilization, WaterShield misting, i-wave multi-stage washing, and a tankless instant heater that most budget bidet seats simply don’t offer. It’s a major upgrade over basic non-electric attachments and even many mid-range electric seats.
What is the main difference between the 400S and 500S?
The two key upgrades on the 500S are the auto open/close lid and the built-in activated carbon deodorizer. Everything else — the i-wave cleaning system, Triple Hygiene Care, heated seat, warm air dryer, and nightlight — is identical across both models.
Do both models require electricity?
Yes. Both the Bidetmega 400S and 500S are electric bidet seats and require a standard 120V outlet near your toilet. If you don’t have an outlet nearby, you’ll need to have one installed, or consider a non-electric option. You can also explore battery-powered portable bidets as an alternative for travel or secondary bathrooms.
Can I use these bidets with round toilets?
Absolutely. Both the 400S and 500S are available in both elongated and round versions. Make sure you select the correct size when ordering to ensure a proper fit. If you’re unsure about what fits your toilet, our guide to bidets for existing toilets can help you figure out compatibility.
Conclusion
The Coway Bidetmega 400S and 500S are two of the most thoughtfully engineered bidet seats on the market right now, and you genuinely can’t go wrong with either one.
If budget is a factor or you just want a clean, feature-packed bidet without every luxury add-on, the Bidetmega 400S is the smart pick.
If you want the full premium experience — auto-open lid, built-in deodorizer, and a completely touchless bathroom routine — the Bidetmega 500S is worth every extra penny.
Either way, both models will dramatically upgrade your daily routine. After using a bidet at this level, reaching for toilet paper will feel like a step backwards — and you can dry off effortlessly with a set of quality bidet towels to complete the experience.
