There are two categories of water heaters, storage and instant. Here, we will explore the differences between them so you may have a better idea of which to use at home.
Instant water heaters are also known as tankless or demand-type water heaters. They provide hot water only when needed, without the use of a storage tank. Here are some examples of instant heaters available in Singapore:
Storage water heaters are heaters that come with an insulated tank. The following are some types of storage heaters. Note that while gas storage heaters are commonly available overseas, they are not sold in Singapore.
Most Singaporeans have several criteria in mind when it comes to selecting a water heater:
- Good Water Pressure
- Consistent Hot Water
- Pairing (what type of heater is suitable for your shower system?)
- Maintenance Level
- Initial Cost
- Running Cost
1. Good Water Pressure
Instant heaters are pressure reducing systems. Flow restrictors are built into every tankless system so that water can be heated instantly when it flows through the heater. Below is a diagram of how an instant system works.
Storage heaters are non-pressure reducing systems or closed systems. Water flows into the tank at high pressure (about 10 lit/min), and is pushed out of the tank at the same flow rate. One storage heater can be shared between two bathrooms. When two simultaneous showers are running, water pressure only drops slightly. Read more about water pressure for shared bathrooms here: 4 Facts about hot water pressure in Singapore
2. Consistent Hot Water
Good hot water pressure and consistent hot water temperature are related. If hot water pressure is low, it means that a lower volume of hot water is being supplied to users. A lower volume means that the hot water supply will not be consistent.
Different instant heaters give you different consistencies of hot water supply. Some background info:
Our body temperature is around 37 ℃. Warm showers require 38℃ of water. Steamy showers require 40℃ of water. 4 lit/min is the minimum water pressure acceptable for a shower.
- Single point: 4 lit/min, can produce 38℃ of hot water
- Multi point: 4 lit/min, can produce 38℃ of hot water
- Gas heaters: 6-8 lit/min, can produce 38℃ of hot water
Single point: This is where single point instant heaters really shine. They never run out of producing hot water at 4 lit/min; you don’t have to worry about running out of hot water.
Multi point: These heaters are supposed to fulfill the needs of several bathrooms. This means their hot water supply is split between two users, that is 4 lit/min divided by 2 users = 2 lit/min. It is almost impossible to shower at 2 lit/min, so with a multipoint heater in Singapore, users cannot shower concurrently. Why do multipoint heaters exist at all if they cannot serve several users at once? This situation is unique to Singapore. Most multipoint heaters overseas are powered at 6 – 12 kilowatts and serve entire households effectively at flow rates of 6 – 12 lit/min. In Singapore, all our heaters are all limited to 3 kilowatts. The multipoint heaters sold here are just not powerful enough for a household.
Gas: Gas heaters can produce more hot water than multipoint heaters at 6 – 8 lit/min. However they are often shared between several bathrooms and the kitchen. This means concurrent users may experience hot water temperature and pressure fluctuations.
- Storage average performance: 10-12 lit/min, can produce 40℃ of hot water
- Storage high performance: 20+ lit/min at 42℃ of hot water
As hot water is drawn from a preheated tank, temperature is both consistent and water pressure is good, even when shared between several bathrooms. It is no surprise that storage tanks are the default choice for high-end facilities.
Storage heaters that are sized correctly will always give you a consistent hot water supply. However, incorrect sizing is very common in Singapore. More on correct sizing here: Sizing your Water Heater.
One glance at the flow rates and maximum hot water temperatures of instant water heaters will tell you that the types of shower systems that can be paired with tankless heaters are limited. Instant heaters can only be used with low flow rate hand showers or special types of rainshowers modified for instant heaters.
Storage heaters have quite an upside potential for producing better water pressure and temperature so you can use them to power almost anything from regular shower heads, rain showers, massage jets and even bathtubs.
Water temperature in a storage tank is very high so you can achieve the “steam effect”. Storage heaters are great for those who are becoming more expectant of the 5-star hotel experience, great water pressure and hot rejuvenating water.
4. Maintenance Levels
- Single point: users feedback up to 5 to 10 years (depends on quality) of using system with no issues
- Multi point: wiring reported to melt often, sometimes within first few months of usage. Probably because these heaters are built to run on higher wattage.
- Gas: Users highly recommended to do bi-annual checks on gas leaks, which can be fatal.
- Electric/Digital: users feedback up to 5 – 10 years (depends on quality) of using system with no issues.
- Gas: not sold in Singapore but will require constant bi-annual checks for gas leaks.
- Heat pump: 5 – 10 years life span, with the exception of washing a small filter once every year.
- Solar: 5 – 10 year lifespan. Solar panels need to be cleaned every 6 months or efficiency will drop, rooftop maintenance is usually costly.
5. Initial Cost
- Single point: 2 showers supplied by 2 heaters at $200 each = $500
- Multi point: 2 showers supplied by 1 heater at $300 each
- Gas: 2 showers, 1 kitchen supplied by 1 heater $250 – $300 each
Storage heaters come in a range of sizes, so if you have a large house, it might be cheaper to get a centralized system.
- Electric: 2 showers supplied by 1 heater, from $200
- Digital: 3 showers supplied by 1 heater, from $650
- Heat pump: 3 showers supplied by 1 heater, from $2600
- Solar: 5 showers supplied by 1 heater, from $3500
6. Running Cost
The running cost of a heater can be estimated by the Energy Factor (EF), an international standard which measures the energy your water heater consumes. The higher the EF, the more energy saving your system.
Instant heaters do not have tanks to store hot water. Hence, there are no standby energy losses with these systems.
- Single point: 0.95*
- Multi point: 0.90*
- Gas: 0.82
Storage heaters come with insulated tanks which are subject to standby heat loss. The better the insulation of the tank, the lower the energy loss. Storage tanks may potentially harness and retain heat from renewable energy sources.
- Electric: 0.90
- Digital: 0.95
- Gas: 0.65
- Heat pump: 2.20
- Solar: 1.20
*EF for single point and multipoint heaters are estimated based on tested EF for demand gas (instant gas heater)
Instant heaters come without a tank, so they are noticeably smaller. This is good for Singaporean homes which are quite compact.
Storage heaters are larger but the most popular sizing among apartments in Singapore are 40 liter tanks. These can fulfill the needs of an average family of 3-4 and easily fit into bathrooms. Should users plan on getting something larger (60 lit and above) to complement their large rainshowers or bathtubs, these heaters may be relocated to the yard or even the aircon ledge.
For private apartments and landed properties which require larger tanks, space is usually not an issue. Floor standing tanks are weatherproof and placement is very flexible. They can be put on the roof or at the garden.
Instant or Storage?
There are many factors to consider while choosing the right water heater for your family. Sometimes your choice may be affected by just one compelling reason – perhaps that huge luxury rainshower? In any case, the shower is one of the few places we can relax and unwind. Whether you prefer quick showers or long steamy ones, there is a water heater suitable for you.
Storage vs Tankless Water Heaters – Green Building Advisor
The Difference Between Storage and Tankless Water Heaters – Building Green