Water Heater Efficiency Ratings Explained > 자유게시판

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While searching for a new water heater, the figures on its packaging may seem cryptic. These ratings indicate how effectively the device converts fuel into hot water, yet they vary in type. Grasping each rating’s definition, measurement, and true cost helps you make a more informed purchase.

Why Efficiency Matters

Heating water is one of the biggest energy drains in a home. Typically, American households spend 5–7% of their yearly electricity costs on hot water. That translates to roughly $150–$200 a year for a typical family. Selecting a unit with a better efficiency rating may lower costs, reduce your carbon impact, and often increase longevity.

Frequently Used Ratings
Annual Fuel Utilization Efficiency (AFUE)

Used for gas and oil tank water heaters.

Presented as a percentage, it indicates the portion of fuel energy that heats water annually.

Take an 80 % AFUE heater: it uses 80 % of the gas for heating, with the remaining energy vented or lost in standby.
EF: Energy Factor

Serves as the contemporary alternative to AFUE for electric and gas tank heaters.

Incorporates standby losses, cycling losses, and the total efficiency of the heater.

Typical EF values: 0.70–0.95. The higher, 名古屋市東区 給湯器 交換 the better.
SEER

They apply to electric heat pumps and air‑conditioners.

hr) against power input (W).

SEER is the average EER over a typical cooling season.

When applied to water heaters, the analogous metric is the Heat‑pump Coil Efficiency of the heat pump, often listed as a "COP" (Coefficient of Performance).
Coefficient of Performance (COP)

It applies to electric heat‑pump water heaters.

It represents the ratio of heat output to electrical input.

A COP of 3 indicates that each 1 kWh of electricity yields 3 kWh of hot water energy.
Recovery Rate

It isn’t expressed as a percent, yet it’s a crucial performance indicator.

It indicates the speed at which a heater can elevate a specified volume of water (e.g., 50 gal) by a set °F.

Expressed in gallons per hour (GPH) or BTU

Essential for families needing lots of hot water at the same time.
Capacity of the Tank

The total amount of water the tank can hold (in gallons).

For tankless systems, the metric is "Gallons per Minute" (GPM).

High capacity or GPM means you’re less likely to run out of hot water during peak use.

Interpreting Ratings as Real Costs

We’ll simplify it with a basic example. Suppose you’re choosing between two 50‑gal electric tank heaters:

- Heater A: EF = 0.75, Recovery = 40 GPH

• Heater B: EF = 0.90, Recovery = 70 GPH

Suppose your household consumes 200 gal of hot water monthly and the electric rate is $0.13

1. Convert the EF into annual energy consumption:

• Heater A uses 200 gal ÷ 0.75 = 266.7 gal‑equivalent energy units.

• Heater B consumes 200 gal ÷ 0.90 = 222.2 gal‑equivalent energy units.

°F, 1°F rise ≈ 1 BTU per lb.

• This is a rough estimate; actual energy cost depends on the temperature rise, but the relative savings are clear: Heater B uses about 16 % less energy.

3. Convert the BTU figure to kWh using 1 kWh ≈ 3412 BTU.

• Heater A: 266.7 gal × 8.34 lb × ΔT ÷ 3412 BTU

• Heater B: 222.2 gal × …

The math shows that even a 15 % improvement in EF can shave $20–$30 off your monthly utility bill, adding up to $200–$300 a year.

Tank vs. Tankless – Which Is More Efficient?

- Tank Heaters

• They maintain a constant hot‑water reservoir.

• Standby losses can be high, especially in cold climates.

• Recovery rate constrains concurrent use; many appliances can deplete hot water.

- Tank‑less Heaters

• They provide hot water on demand, removing standby losses.

{• Higher EF or COP values (often 0.95–0.99 for electric, 3–4.5 COP for heat pumps).|• They usually boast higher EF or COP (often 0.95–0.99 for electric, 3–4.5 COP for heat pumps).|• They typically achieve higher EF or COP (usually 0.