Storage vs instant water heater: choosing the right geyser
Capacity, star rating and the hidden cost of standing heat loss. How to pick a water heater that fits the way your household actually uses hot water.
Vikram Mehta
Head of Sales & Distribution
· 5 min read
Storage or instant
An instant (tankless) heater warms water on demand and suits a kitchen sink or a single quick shower. A storage geyser holds a tank of hot water and suits bathing, especially for more than one person back to back.
The rule of thumb: instant for low, intermittent use; storage where you need several litres of hot water in one go.
Sizing the tank
For bathing, roughly 10–15 litres suits one person, 25 litres a small family bathroom, and 35 litres or more where a bathtub or multiple users are involved. Oversizing wastes energy keeping water hot that nobody uses.
Pressure rating matters too — a high-rise flat with a pressure pump needs a geyser rated for it, or the tank will not last.
Running cost and solar
A higher BEE star rating means thicker insulation and lower standing loss, which is where a storage geyser quietly spends money between uses. Over a geyser's life the running cost dwarfs the purchase price.
If you use a lot of hot water, ask us about a solar water-heating system — it can cover most of the year's demand and pairs well with a small electric backup. We carry Havells, Racold, Bajaj, AO Smith and Crompton.
Written by Vikram Mehta, Head of Sales & Distribution at Callisto. If something here contradicts your own experience, we would genuinely like to hear it.
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