Test method

How we test geysers and water heaters

The uses we score and the tests we run on every geyser: heat-up time, hot water at a 40 °C mix, overnight heat loss, scale and winter power use.

Geysers & Water Heaters reviews

Every geyser we review is installed on a wall in a real Indian home, on the household’s own supply, and used daily for four to seven weeks, on the unit we bought or borrowed. Storage geysers all go through the same heat-up, 40 °C mix, overnight loss, scale and energy tests, so a 31-minute heat-up or a 6 °C overnight drop means the same thing on every model. We note the water’s TDS for each review, because scale depends as much on the supply as on the tank.

Instant electric geysers run the same tests on their smaller tank, and gas geysers are measured on time to hot water, flow at a 40 °C mix and LPG use. Each test result in a review links back to the matching test on this page.

What we score

Morning baths for a family
Whether one heat-up gives enough water at a bathing temperature for two or more bucket baths, and how long the family waits for it in winter.
Kitchen sink and wash basin
How quickly it gives a small amount of hot water for washing up and short washes, and whether it wastes energy if left on.
Hard water and long life
How much scale builds on the element on hard Indian water over several weeks, and what the tank lining and warranty promise for the years after.
Power cuts and weak wiring
Whether it keeps giving hot water during a power cut, and what it asks of the inverter, MCB and wiring in an older flat.

The tests

  1. Full tank, 15 °C to 60 °C

    Measured in min Lower is better

    We fill the tank from a 15 °C supply and time how long the full tank takes to reach 60 °C at the outlet. Storage geysers and instant geysers with a small tank both run this test on their own tank size.

  2. Full tank, 9 °C winter inlet to 60 °C

    Measured in min Lower is better

    We repeat the heat-up timing with winter inlet water at about 9 °C, as in a north Indian January, to show how much earlier you need to switch on in the cold months.

  3. Hot water at a 40 °C mix

    Measured in L Higher is better

    From a full tank at 60 °C, we draw water mixed with cold supply to a 40 °C bathing temperature and measure how many litres come out before the mix starts to cool.

  4. Heat loss over eight hours

    Measured in °C Lower is better

    We heat the tank to 60 °C, leave it for eight hours in a closed bathroom at about 18 to 19 °C without drawing or reheating water, and measure how far the water temperature falls.

  5. Electricity per day in winter

    Measured in kWh/day Lower is better

    We meter the geyser's electricity over a typical winter week of household use, mostly morning bucket baths, and report the daily average. The note says how many people used it and how.

  6. Scale on the element

    After several weeks of daily use on the home's own supply, we open the fittings and inspect the heating element or heat exchanger, and describe the scale we find alongside the water's TDS.

  7. Time to hot water at the shower

    Measured in s Lower is better

    For gas and other continuous-flow geysers, we time how long hot water takes to reach the shower after the geyser ignites.

  8. Continuous flow at a 40 °C mix

    Measured in L/min Higher is better

    For gas and other continuous-flow geysers, we measure how many litres a minute the geyser holds at a 40 °C mix at the shower.

  9. LPG use per month

    Measured in kg/month Lower is better

    For LPG geysers, we track cylinder use over the test period for the household's normal winter baths and report kilograms of gas a month.