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Consider a gas one. I used such a thing when I lived in a cold place - No issues at all as long as you have good water flow.

Thanks Fred, but the bathroom is wired for electricity only.

I’m about to move into an unfurnished apartment. Bathroom doesn’t even have water heater, and there’s no central heating. There’s already holes drilled and wiring for an instant water heater, because person who lived there previously had one.
My experience using these heaters in hotels is that they all cut the water volume down tremendously. I hate that. It means it takes me twice as long to shower. Some sales clerks told me that some of the more expensive heaters, like Ariston, are better in this regard, and have some kind of pump that makes the water come out faster with more volume.

I know the tank style heaters that hang on the wall and hold 30 or more liters probably don’t have this problem. But they would be more difficult to install because apartment has pre-cut holes and wiring drilled for the small instant water heaters.

I never use hot water, just lukewarm water. But my experience with these machines is that even if you set the heat to minimal, the water volume is still just as low as if you set the heat to maximum.

What are your experiences and opinions about these water heaters. Any recommendations for a good one? Thanks for replies.
-@ChoculaD

My experience.................... Make sure its one with a built in pump, it makes a big difference. They usually have 2 control knobs, 1 for temperature & 1 to switch on the pump & adjust the water pressure/volume.

I’m about to move into an unfurnished apartment. Bathroom doesn’t even have water heater, and there’s no central heating. There’s already holes drilled and wiring for an instant water heater, because person who lived there previously had one.
My experience using these heaters in hotels is that they all cut the water volume down tremendously. I hate that. It means it takes me twice as long to shower. Some sales clerks told me that some of the more expensive heaters, like Ariston, are better in this regard, and have some kind of pump that makes the water come out faster with more volume.

I know the tank style heaters that hang on the wall and hold 30 or more liters probably don’t have this problem. But they would be more difficult to install because apartment has pre-cut holes and wiring drilled for the small instant water heaters.

I never use hot water, just lukewarm water. But my experience with these machines is that even if you set the heat to minimal, the water volume is still just as low as if you set the heat to maximum.

What are your experiences and opinions about these water heaters. Any recommendations for a good one? Thanks for replies.
-@ChoculaD

Hi ChoculaD. I have used these types of heaters here in VN for a few years now, and have no problem with them.

A decent heater/pump will run you around 3.5 - 4 million VND. The heat setting is independent of the pump, so the water pressure remains the same whether you have the heat at minimum or maximum. Be careful, as the heater can heat the water to a very high temperature.

I can't remember the name of the two previous heaters I bought and installed in my 2 bdrm home in Saigon, but they had a logo on the front picturing a dolphin. I've since installed them (myself) in the homes of two VN friends of mine as neither had hot water, and reports are that they are still working fine after almost 6 years.

I recently purchased/installed one in one of the bathrooms in the home I am in now in Phu Quoc. There is a solar heat system here, but it wasn't functional when I first moved here (it is now) so I threw for the heater. The current one is made by a company called "Ferroli". My advice is to not go cheap. Pick one with an internal pump (not all have it), mid-range price.

@goodolboy Thanks, some of the Ariston models have a pump

But the heaters have to reduce water volume in order to heat instantly. So how is a pump going to change that fact? If it pumps more water per second, the water will have to be cooler.

Can you install these and still keep the unheated shower available? Because most of the year, unheated water in VN is a comfortable temperature, and of course much greater volume. So is there an adapter you can use to split the water from the unheated tap, with one hose going to the heater, and one available to use without the heater?

Once at a hotel in Thailand, I had a water heater that gave really good spray and volume.  I was so impressed with it. It was a Sharp WH-33 and it still seems to be sold in Thailand but I can't find it in VN.

Sorry for all my silly questions! Suddenly I have to buy a houseful of stuff that I haven't had to buy in many years.

Can you install these and still keep the unheated shower available? Because most of the year, unheated water in VN is a comfortable temperature, and of course much greater volume. So is there an adapter you can use to split the water from the unheated tap, with one hose going to the heater, and one available to use without the heater?
-@ChoculaD

yes you can, just turn the heat control knob to cold & the pump control knob right up to max & bobs yer uncle!....power shower.

Cam on. So you're saying the volume DOES increase independently of the temperature control on pump models. Which model do you use?

@ChoculaD you could just take cold showers instead?

@ChoculaD following up on ‘GoodolBoy’ comments. Before purchasing an on demand unit read the volume flow specs. It could be their selling pitch. Without an internal pump one’s depending on the house/apartment water pressure, often times less than one would like. I lived one year using an on demand elect heater. The unit had an internal pump with gravity fed water from the roof tank. The volume was good, downside, the pump noise was nothing less than a NOT pleasant morning wake-up. Perhaps the sound decibels are included in the unit’s specs.

@ChoculaD following up on ‘GoodolBoy’ comments. Before purchasing an on demand unit read the volume flow specs. It could be their selling pitch. Without an internal pump one’s depending on the house/apartment water pressure, often times less than one would like. I lived one year using an on demand elect heater. The unit had an internal pump with gravity fed water from the roof tank. The volume was good, downside, the pump noise was nothing less than a NOT pleasant morning wake-up. Perhaps the sound decibels are included in the unit’s specs.
-@River Frogs

IT may have been cavitating) air in the line somewhere, consistently replenishing itself.

Ours, two showers in house we built, gravity fed from roof mounted tank and solar heater. Not wildly breath taking pressure, but gets the job done

MAc.

@ChoculaD following up on ‘GoodolBoy’ comments. Before purchasing an on demand unit read the volume flow specs. It could be their selling pitch. Without an internal pump one’s depending on the house/apartment water pressure, often times less than one would like. I lived one year using an on demand elect heater. The unit had an internal pump with gravity fed water from the roof tank. The volume was good, downside, the pump noise was nothing less than a NOT pleasant morning wake-up. Perhaps the sound decibels are included in the unit’s specs.
-@River Frogs

I must say that the 2 water heaters with pumps I have had experience with have not been noisy, but you do need a good head of water supply to the pump otherwise as Froggy said you will get the pump cavitating & that will cause a right rattle & also eventually damage the pump!

But the heaters have to reduce water volume in order to heat instantly. So how is a pump going to change that fact? If it pumps more water per second, the water will have to be cooler.
-@ChoculaD

Not on mine, and others I've worked with.

The water flows through a coil. The coil itself is heated. Whether you choose to energize/electrify the coil or not doesn't affect the flow of the water.

Not all of these units have a variable pump pressure control (nor even a pump, for that matter), but all have temperature control.

@River Frogs Thanks. I hope volume flow specs are available on these things. Salespeople will probably not know. The water volume and pressure in the apartment is strong coming from the unheated shower.

I'd still like some actual brand and model recommendations of the heaters you're happy with, if that's not classified information

I'd still like some actual brand and model recommendations of the heaters you're happy with, if that's not classified information
-@ChoculaD

Unfortunately I don't know if it's available here in Vietnam, but while I was in Mexico the winter of 2021/2022, I purchased the Bosch Nova 7 LP Gas model and a good water pump to service my 2nd floor apartment, with great results.

I'd still like some actual brand and model recommendations of the heaters you're happy with, if that's not classified information
-@ChoculaD

I can't remember the name of the two previous heaters I bought and installed in my 2 bdrm home in Saigon, but they had a logo on the front picturing a dolphin......reports are that they are still working fine after almost 6 years. The current one is made by a company called "Ferroli". My advice is to not go cheap. Pick one with an internal pump (not all have it), mid-range price.  -@Aidan in HCMC

Ferroli, model MIDO-MSP 4.5S with "Silent Pump"

Just one piece of advice for people new to these units.

These units are not intended to have hot water run into them.

@ChoculaD I have never had any issues with instant water heaters.

What is the water pressure in the bathroom? If it is low, you'll have to get a heater with a pump.

The smaller heaters have smaller the coils inside the heater that will make the water come out at a lower pressure.

There is no other mechanism inside the heaters to reduce the water volume.

Get a decent one and preferably with a pump if you it if the pressure is low in the bathroom.

@ChoculaD  (for just using cold water in summer) Easiest solution would be to get the plumber take a offshoot of the cold water and have a tap installed where the water can go to a separate hot water out-take without have to operate the heater.