Everything! Looks good, performs well, and has saved me a fortune on electricity. If I could sleep with it I would but my wife gets so jealous that I am afraid to take the chance. My best friend is renting and he has been trying to persuade his landlord to put one in but so far, he is behaving like so many other landlords do. It might have been a mistake to tell him about my wonderful heater as the relationship with his landlord is deteriorating fast, which is sad, because he fancies the landlords wife.
Price, Performance, Economy.

21e - hopeless having this unit if you rely on electricity as well - when you have a power blackout you don't get hot water - even though it is a gas unit. Bought this house 18 months ago, unit is not too old and the i am going to replace this with an instantaneous gas unit.

No hot water in power blackout.

Hi, we are temporarily renting and there is a Bosch 21e unit installed, not sure how old. The problem we have is that when it rains we have no hot water. Not sure if it is the moisture in the air that causes this. We can hear the spark trying to ignite, there is smell of gas but no hot water. The only thing we're sure of is that when it rains we have cold showers.

Not happy far from it we brought a new g j gardner home two years ago and this system was already in place we are disappointed with this unit.

Every time we want hot water we have to run the tap flat out for approximately up to a minute before the warm to very mild hot water comes out which is not suitable for washing dishes so we have learnt to live with this and we boil the water when we want to wash the dishes.

I cannot believe we have not complained about this until now.

My Bosch Highflow e21 is dangerous, the unit turns itself on when I haven't even turned a tap, there is gas smell coming from the unit even when its not running, the last cylinder only lasted a month,and we are a two person household only using gas for the hot water. would not recommend this product

Bought a house with 21E version in and I cannot wait to get rid of the silly thing. Very hard to keep the shower warm, it is either 50C or freezing cold. Am unable to use the water to wash the dishes in as, it is just not hot enough. Hot water is limited to 50C. Would not reccomend to anyone.
System runs quiet
Water goes from hot to cold. No other taps in the house were touched and it still goes cold after a minute. Water only at 50C so useless for washing dishes in. No hot water if power goes out.

What is wrong with the rest of you? This machine (21E) works great!!! We love it! Temp only fluctuates if another tap is turned on. We would not hesitate to buy another one! Make sure you have it installed properly by a professional, then you'll have no probs, like us!
Delivers constant hot water always. Great when you have people staying, & you never run out of hot water.
Takes a while for the hot water to hit our kitchen sink (furtherest point from the heater), so a lot of water is wasted. Fluctuates in temp only when another tap is turned on.

My 21e is an $800+ enviromental disaster It has to use too much water and therefore more gas. This is totally against the principles of an instantaneous hot water. I can't find any reference to this min. flow rate in instructions, only a false statement that if run below 2.5 L/min. the temp. could be unstable (on page 15) It will be unstable according to Bosch, when you ring them, below 9L/min. This is true.
At first it appeas to save on energy use, but all models must have a water flow rate of more than 9 lit/min. in the shower-much too high for drought areas.
Unless you shower is a fire hose the temperature control is a joke. This is a serious safety factor. It saves gas because the water is often dead cold.