Generally there 2 types of water heaters – instant and storage
Most of us shouldn’t be stranger to instant heater since it’s popular since the 80s till to date. Just switch it on & u get hot water almost immediately.
However for instant heater, there are 2 kinds – 1 run by electricity, 1 run by gas. For the former, it’s commonly found. In recent yrs and many countries, there’s an increased interest to install gas instant heater simply becos of few reasons – 1) run by gas, so less cost since its tariff much lesser than electricity’s (2) u need not switch the heater on and off since it will turn on its heater instantly when it detects running water in the hot water pipe. (3) the gas heater produce very hot water. Shiok, haha The main disadvantage would be, since it runs on gas, it will need to be installed in the kitchen, so might be eye sore to some.
The next category, storage heater, is favoured too since it could be turned on half an hr before bath and switch off. The hot water let’s say 20L can last u for an evening bath. Some even stated that the water will remain warm in the following morning. However it has its own shortcoming too (1) not instant, meaning u have to turn on heater early before bath (2) electricity-thirsty since u need to heat 20L of water (3) u cant enjoy long bath/shower since u’re confined to 20L of hot water (4) it has a higher price (5) rather big and bulky, eyesore
However, my opinion might be skewed since I use an instant gas heater. Others using storage heater may shed more light on their choice and reasons behind it.