Instant water heaters generally consume more electricity per use compared to traditional heaters, but they can be more efficient overall due to reduced standby losses.
Instant water heaters provide hot water on demand without a storage tank. But do they consume more electricity than traditional tank heaters? The answer depends on usage patterns, heater type, and efficiency factors.
How Instant Water Heaters Work
Instant water heaters (also called tankless or on-demand heaters) heat water directly as it flows through the unit. When you turn on a hot water tap:
- Cold water enters the heater
- Electric elements or gas burners instantly heat the water
- Hot water flows to your faucet or shower
This differs from storage heaters that keep 20-80 gallons of water hot 24/7. For homes using under 41 gallons daily, tankless heaters can be 24-34% more energy efficient.
Electricity Consumption: Instant vs Storage Heaters
Power Draw During Use
Instant heaters use more power while operating than storage heaters:
| Heater Type | Typical Wattage |
|---|---|
| Electric Instant | 8,000-36,000W |
| Electric Storage | 3,000-5,500W |
The higher wattage is needed to heat water instantly as it flows. Storage heaters heat water gradually over time.
Standby Energy Loss
Storage heaters constantly lose heat through tank walls (standby loss), requiring frequent reheating. Instant heaters have zero standby loss since they don’t store hot water.
Total Energy Use
For most homes, instant heaters use less total electricity despite higher power draw during use. The elimination of standby losses typically outweighs the higher operating wattage.
Factors Affecting Electricity Consumption
Hot Water Usage Patterns
Instant heaters save the most energy for:
- Homes using under 41 gallons daily
- Households with intermittent hot water use
Large families with continuous hot water needs may see less savings.
Heater Size and Flow Rate
Oversized instant heaters waste energy. Proper sizing is critical:
- Small units (2-4 GPM) for 1-2 people
- Medium units (5-7 GPM) for families
- Large units (8+ GPM) for whole-home use
Temperature Settings
Each 10°F increase in temperature setting can raise energy use 3-5%. Set to 120°F for optimal efficiency.
Maximizing Instant Heater Efficiency
Proper Installation
Have a professional install your heater to:
- Ensure correct electrical wiring
- Optimize water flow
- Prevent heat loss in pipes
Maintenance
Regular maintenance improves efficiency:
- Descale annually (hard water areas)
- Clean inlet filters
- Check for leaks
Usage Tips
- Space out hot water use (avoid simultaneous showers/appliances)
- Install low-flow fixtures
- Consider point-of-use heaters for distant faucets
The Bottom Line
While instant water heaters have higher power draw during use, they typically consume less total electricity than storage heaters by eliminating standby losses. Proper sizing, installation, and maintenance ensure maximum efficiency. For most households, an instant heater is the more energy-efficient choice.
