Water Heater Efficiency Ratings Explained > 자유게시판

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. Knowing the meaning, measurement, and actual cost of each rating can guide you to a wiser choice.

The Importance of Efficiency

Heating water is one of the biggest energy drains in a home. On average, U.S. homes allocate roughly 5–7% of their annual electric bill to 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.

Common Efficiency Ratings
Annual Fuel Utilization Efficiency (AFUE)

Applicable to gas and oil tank heaters.

Expressed as a percentage, it represents how much of the fuel’s energy is actually used to heat water over a year.

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

It supersedes AFUE for electric and gas tank units.

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

Typical EF figures: 0.70–0.95; the greater the number, the superior the efficiency.
EER

They apply to electric heat pumps and air‑conditioners.

hr) against power input (W).

SEER averages EER throughout a typical seasonal cycle.

In water‑heater terms, the corresponding measure is the Coil Efficiency of the heat pump; brands usually refer to it as a "COP" (Coefficient of Performance).
Coefficient of Performance (COP)

Used for 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

Not a percentage, but a key performance metric.

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

hr.

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

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

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

A larger capacity or GPM reduces the chance of running out of hot water during peak demand.

How Ratings Translate to Real Costs

Let’s illustrate with a straightforward example. Imagine you’re comparing two 50‑gal electric tank heaters:

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

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

kWh.

1. Translate EF into yearly energy usage:

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

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

2. Convert gallons to BTU (1 gal ≈ 8.34 lb, 1 lb ≈ 1 BTU

• It’s a rough approximation; real energy cost hinges on temperature rise, yet the savings are evident: Heater B consumes ~16 % less energy.

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

kWh.

• 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 may be significant, particularly in colder regions.

• Recovery rate limits simultaneous usage; you can run out of hot water if many appliances are on.

- On‑Demand Heaters

• They heat water as needed, eliminating standby losses.

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