Hot Water Heater: Storage Water Heater vs Tankless Water Heater

Residential plumbing system is a system which provide water in a house to carry out various house hold activity. Residential plumbing system is an integral part of house and without it one cannot think about the hot and cold-water supply or drainage.

Two types of hot water system provide hot water in the house. One is localized hot water system and other is centralized hot water system. To know more, read hot water system. Hot water is required in house for various purposes like cooking, bathing, cleaning, etc. Water Heaters are installed/fitted for heating water and are connected to various appliances. To supply the hot water from the water heater, generally Copper pipes, Polyethylene (PB) pipes, Chlorinated Polyvinyl Chloride (CPVC or PVC) pipes, Random Polyproylene (PP-R) pipes, Cross linked Polyethylene (PEX) pipes are used in hot water system. There is no difference between water heater and geyser, when water heater is used for domestic purpose, it is denoted by the geyser in many countries. Fuels commonly used in water heaters are electricity, gas, oil and solid fuel i.e. wood and biomass and even solar energy is used. Water heaters are of two types: Storage Tank Water Heater and Tank less Water Heater irrespective of fuel used for heating.

Also Read: Solar Water Heater: Types & Their Uses

We have already mentioned the variations between the electrical water heater vs gas water heater vs solar water heater. Here we discuss the differences between the storage water heater and tank less water heater / instant hot water heater.

Differences Between the Storage Water Heater and Tankless Water Heater/Instantaneous Heater:

Storage Water Heater
Instantaneous Water Heater

How Hot Water Heater works?

Storage Water Heater

  • In Storage Water Heater water is first filled  in the tank and then heated. It needs time to heat the water i.e hot water is not instantly available. One has to switch on before you want to use, if it is an electric heater.
  • When water is heated, thermostat will sense water temperature and automatically stop further heating.
  • Only the amount of water in the tank is heated i.e quantity of water available would depend on capacity of heater.
  • Once the hot water is used tank gets refilled and water is heated again in tank, which will need time.

Instantaneous  Heater/Tankless Water Heater

  • In Tankless Water Heater incoming cold water enters through inlet, passes through heat exchanger in which it gets heated and hot water is instantly available at outlet. One don’t have to wait.
  • Switch has to be turned off to stop the heating of incoming water.
  • All the water coming is heated on time continuously.
  • Once the water is used, incoming water is heated and hot water is available continuously.

Components of Hot Water Heaters

Storage Water Heater

  • It consists of thermally insulated vessel (tank), thermostats (temperature sensitive device), pipes and heating elements (either electric heating or gas burners).

Instantaneous  Heater/Tankless Water Heater

  • It consists of switch, small pressure vessel with heat exchanger and a pilot lamp (a lamp that lights up when circuit is closed). The heater is to be switched off immediately after use, hence no thermostat is required.

Carbon Dioxide (CO2) Emissions of Hot Water Heaters

Storage Water Heater

  • CO2 emissions are more.

Instantaneous  Heater/Tankless Water Heater

  • CO2 emissions are less.

Life of Hot Water Heaters

Storage Water Heater

  • Life span is 10 to 12 years.

Instantaneous  Heater/Tankless Water Heater

  • Life span is about 20 years.

Pros and Cons of Hot Water Heaters

Storage Water Heater

  • Continuous hot water flow is not available.
  • Hot water stored in the tank constantly looses heat.
  • These heaters affect the quality of water due to storage of water in tanks.
  • Hot water flow is available as soon as hot water tap is turned on, of course allowing initial heating time which maybe 10 to 20 minutes depending upon its capacity.
  • If temperature of hot water reduces below 60° C water stored in tank gets contaminated due to breeding of bacteria.
  • Suitable for large establishments.
  • More pipe line causes heat loss during conveyance of hot water from storage water heater to the fixture.
  • The flow (quantity of water coming from tap) and velocity (the speed at which water comes) is good. Hence, better for use; provided capacity is adequate.
  • More advisable and suitable when used with combined taps (hot and cold water) i.e with mixer body, diverter, etc.
  • It can be common for more than one bathroom of a house, reducing capital cost.

Instantaneous  Heater/Tankless Water Heater

  • Continuous hot water flow is available.
  • Do not generate standby energy (heat) losses.
  • Water quality is not affected because water is not stored.
  • Exchanger first builds up the temperature and then hot water come sand hence may take few minutes or more.
  • No water contamination as no water is stored in heater.
  • Suitable for small establishments
  • Less heat loss due to short pipe length for conveyance of hot water.
  • The flow and velocity both are comparatively less than storage water heater and hence not very comfortable where more water is required.
  • Not suitable as less water flow.
  • It can be common for more than one bathroom, provided it’s a gas gyeser. Not possible in case of electric gyeser, as seperater electric gyesers are needed for all bathrooms.

Cost of Hot Water Heaters

Storage Water Heater

  • Capital cost i.e initial cost is more.
  • More suitable for shower, bathtubs, etc.
  • Needs more space due to tank.

Instantaneous  Heater/Tankless Water Heater

  • Capital cost is less but uses more power in case of electric gyeser. Gas gyesers are cheaper than electric.
  • Less suitable for shower, bathtubs, etc.
  • Acquires less space, except electric.

Fuels for Hot Water Heaters

Storage Water Heater

  • Electricity – Electrical Storage Water heaters.
  • Gas – Gas water heater.
  • Solid Fuel (wood, coal, biomass, charcoal) – Boilers
  • Solar Water Heater

Instantaneous  Heater/Tankless Water Heater

  • Electricity – Geysers (Instantaneous Water Heaters)
  • Gas – Gas Geysers
  • Electricity – Geysers (Instantaneous Water Heaters)
  • Gas – Gas Geysers

Buying Guide of Hot Water Heaters

Storage Water Heater

  • These heaters are sold as per the capacity i.e minimum amount (gallons/liters) of water a geyser can deliver. Eg: A 30 gallon storage heater will store and yield 30 gallons (114 L) of water. One may choose based on family size. Make choice of heater accordingly
  • First Hour Rating (FHR) is taken into consideration. It is the number of gallons of hot water the heater can supply per hour(starting with a tank full of hot water). More FHR means more quantity of hot water available.

Instantaneous  Heater/Tankless Water Heater

  • Theses heaters are sold on the basis of quantity of water required at fixtures. Normally this is the water quantity required.
  • Gallons per Minute rating (GPM) i.e quantity of water flow available per minute is taken into consideration. Ex: A 6.5 GPM water heater will deliver 6.5 gallons (25L or 1 bucket) water in 1 minute.
  • Always choose more efficient (more stars) water heater.

Bottom line: Tankless water heater saves energy as well as quality of water is maintained where as if economy is priority and more hot water is required than one should opt for storage water heater.

Must Read:

Subsidy on Solar Water Heater System
Decide the Capacity of Solar Water Heater for your Home
Solar Water Heater: Requirements of Cost & Maintenance
Problems of Solar Water Heaters

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Nidhi Patel





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