A storage geyser and an instant geyser are built for different jobs. Here is how they differ on heating time, running cost, wiring, space and hard water, with worked numbers.
Most people ask "geyser or instant geyser?" as if one is simply the faster, cheaper version of the other. They are not. A storage geyser heats a large tank and keeps it hot, so you can run a full bath or shower. An instant geyser (also sold as a "instant water heater") heats a small tank, usually 3 litres, in a couple of minutes. It is meant for a kitchen sink or a basin, not for bathing.
Choosing wrongly is the main mistake here. Put an instant geyser in the bathroom and you will wait, then run cold. Put a storage geyser in the kitchen and you will pay for a large tank and a long wait when you only wanted warm water for dishes. This guide explains which fits where, with the numbers behind it.
A storage geyser holds 10 to 25 litres or more, heats it with an element, and a thermostat switches the element off when the water reaches the set temperature. Hot water is drawn from the top and cold water enters at the bottom. Because the tank is insulated but never perfect, a small amount of energy goes into keeping the water hot while you are not using it.
An instant geyser has a small tank, commonly 3 litres, with a high-power element, often 3 kW. The tank is small enough that the element brings the whole volume to temperature in a few minutes. Many models can also be switched off immediately after use, so there is little heat left waiting around.
Basic physics gives you a feel for the difference. Heating one litre of water by one degree takes about 4.18 kilojoules.
Heating time
What happens when the small tank runs out At 3 kW, an instant geyser can add about 35°C of heat to only roughly 1.2 litres of water per minute. So the first 3 litres arrive hot. After that the output is a trickle of hot water, or lukewarm water if you open the tap fully. This is why it suits washing up and not showers.
Rough running cost Heating 20 litres of water from about 22°C to 45°C for a bath takes about 0.53 kWh of electricity before any losses. At ₹8 per unit, that is roughly ₹4.30 per bath. The same energy is needed whichever geyser type supplies the water. These are estimates, not measurements. Your tariff, incoming water temperature and how long the geyser stays switched on will change them.
Capacity. Storage: 10 to 25 L and up. Instant: usually 3 L, with a few larger "rapid" models around 6 L.
Waiting time. Storage: 20 to 45 minutes from cold. Instant: about 2 to 4 minutes.
Power drawn at once. Storage: commonly about 2 kW, around 9 amps. Instant: commonly 3 kW, around 13 amps.
Standing losses. Storage: some, because it keeps water hot. Instant: very little, if you switch it off after use.
Space. Storage: a wall-mounted tank, 15 to 25 L, in the bathroom or on a balcony. Instant: a small cylinder that fits under a kitchen counter or above a basin.
Hot water volume. Storage: enough for one to three people to shower. Instant: a few litres, then a trickle.
Price on Amazon.in (10 Nov 2026). The storage geysers below were listed at about ₹7,000 to ₹8,500. The instant geysers were about ₹3,100 to ₹3,400.
A 3 kW instant geyser draws about 13 amps (3,000 W divided by 230 V). That is a heavy load for an ordinary light-duty socket. Makers ask for a 15 or 16 amp power point, wiring of a suitable thickness, a correctly rated MCB and a working earth connection. If your kitchen wiring is old, get an electrician to check it before you install one. A weak socket can overheat.
A storage geyser at 2 kW draws about 9 amps, which is lighter, but the same rules on earthing and a proper MCB apply. Always switch off at the isolator before anyone touches a unit that has water leaking near it, and never let a child handle the controls.
Both types suffer from scale if your water is hard. Scale on the heating element slows heating and makes the unit work harder. Orient Electric, a geyser manufacturer, advises checking the thermostat setting (50 to 60°C is its suggestion) and descaling when heating times have clearly lengthened over weeks or months. Descaling the tank or element means draining the unit, so if you are not comfortable with that, have it done through the manufacturer's service.
Storage tanks are also worth inspecting if the geyser is several years old. Leaks from the tank body, rust-coloured water or a persistent smell all need a technician.
Choose a storage geyser if:
Choose an instant geyser if:
Choose both if: the kitchen is far from the bathroom, or you are tired of waiting for hot water for dishes.
These four are all on Amazon.in. Prices and ratings were checked on 10 Nov 2026. Check the live listing for the current price, warranty and installation notes before you order.
| # | Product | Best for | Link |
|---|---|---|---|
| 1 | AO Smith SDS-GREEN-025 25 Litre 5 Star Storage Water Heater | Storage 25 L | Check price |
| 2 | AO Smith 15 Litre 5 Star Storage Geyser (2 kW) | Storage 15 L | Check price |
| 3 | Havells Instanio 3L Instant Water Heater | Instant 3 L | Check price |
| 4 | V-Guard Zio Instant Water Geyser 3L | Instant 3 L, lower price | Check price |
A 25 litre vertical storage geyser with a BEE 5 star rating. Listed at about ₹8,499 and rated 4.4 out of 5 by 12,530 buyers on Amazon.in on 10 Nov 2026.
Skip it if you only need hot water at a sink.
A 15 litre, 5 star BEE storage geyser with a 2 kW element. Listed at about ₹6,999 and rated 4.2 out of 5 by 5,659 buyers on Amazon.in on 10 Nov 2026.
Skip it if more than two people shower one after the other.
A 3 litre instant water heater for kitchen and basin use. Listed at about ₹3,412 and rated 4.2 out of 5 by 14,367 buyers on Amazon.in on 10 Nov 2026.
Skip it if you want to shower from it.
A 3 litre, 3000 W instant geyser. Listed at about ₹3,149 and rated 4.2 out of 5 by 7,604 buyers on Amazon.in on 10 Nov 2026.
Skip it if your wiring cannot carry a 3 kW load.
For more options by size and budget, see our guides to the best water heaters and the best instant geysers.
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Not for bathing. The common 3 litre instant geysers are made for a kitchen sink or wash basin. Once the small tank is used up, the water heats at only about a litre per minute, so a bucket bath is slow.
For the same amount of hot water the heating energy is about the same. A storage geyser also loses some heat while it waits at temperature, and an instant geyser does not, but the instant geyser draws more power at once. Habits (how long you leave it on) matter more than the type.
A 3 kW instant geyser draws roughly 13 amps. Manufacturers ask for a 15 or 16 amp socket and a suitably rated MCB, with proper earthing. Have an electrician check this before you install one.
The BEE label shows energy use, and more stars means higher efficiency. For a geyser you run daily, the extra stars are worth paying a little more for.
Roughly 15 litres suits one or two people, and 25 litres suits a family of three to four, though this depends on how much hot water you use and how cold your winters are.
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