# Water Heater Electricity Cost: Storage vs Instant Heater

Compare the monthly electricity cost of a storage vs an instant water heater for your household, by heater power and usage, at SP's Oct to Dec 2026 tariff.

Interactive tool: https://lookup.sg/tools/water-heater-cost-calculator

## How this works
An instant (tankless) heater runs at its full rated power only while a shower is on, so its energy is rated kW × total shower time per day. The default 3.3 kW is an assumption; check the rating plate on your unit.

A storage heater heats a tank until its thermostat switches off, so its energy is rated kW × the time it spends heating each day (an assumed 45 minutes at 2.5 kW by default). If it is left on 24 hours, an assumed standby loss of 1 kWh a day is added for the heat that leaks from the tank.

Monthly cost = kWh per day × 30 days × SP Group's regulated tariff of 31.16 cents per kWh including GST (28.59 cents before GST) for 1 October to 31 December 2026.

## FAQs
### How much electricity does a water heater use in Singapore?
For 3 people taking 10-minute showers, a 3.3 kW instant heater uses about 1.65 kWh a day (49.5 kWh a month), which costs about S$15.43 a month at the October to December 2026 tariff.

### Is a storage or instant water heater cheaper to run?
With the defaults here, an instant heater costs about S$15.43 a month and a 2.5 kW storage heater heating for 45 minutes a day about S$17.53. Leaving the storage heater on 24 hours adds an assumed 1 kWh a day of standby loss, taking it to about S$26.88.

### Should I switch off my storage water heater?
Usually yes. Keeping the tank hot all day adds standby losses, about S$9.35 a month at an assumed 1 kWh a day and 31.16 cents per kWh. Switching on 30 to 60 minutes before showers avoids most of it.

## Sources
- [SP Group: Tariff information (Oct to Dec 2026)](https://www.spgroup.com.sg/our-services/utilities/tariff-information)

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Source: Lookup (https://lookup.sg) · Data as of October 2026 · Listings compiled from Singapore government open data (data.gov.sg), OneMap and Overture Maps places. Free listings never show contact details; contact details appear only on Lookup Verified listings.