When you’re looking to buy a new water heater, the numbers on the packaging can feel like a secret code. 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.

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. It amounts to approximately $150–$200 per year for a typical household. Choosing a unit with a higher efficiency rating can reduce that cost, lower your carbon footprint, and 名古屋市東区 給湯器 交換 often come with a longer lifespan.

The Most Common Ratings
Annual Fuel Utilization Efficiency (AFUE)

Designed for gas and oil tank water heaters.

Shown as a percent, it shows how much of the fuel’s energy goes into heating water throughout the 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.

It accounts for standby, cycling losses, and the overall unit efficiency.

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

These are for electric heat pumps and air‑conditioning units.

hr) to electric input (W).

SEER is the average EER over a typical cooling season.

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

Used for electric heat‑pump water heaters.

It measures heat energy supplied against electrical energy used.

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

It’s not a percentage, but it remains a vital performance metric.

Describes how quickly a heater can raise the temperature of a set volume of water (e.g., 50 gal) by a certain number of degrees.

It’s expressed in gallons per hour (GPH) or BTU

Important for households with high simultaneous hot‑water demand.
Volume Capacity

It’s the maximum water volume the tank can contain (in gallons).

For tankless models, it’s expressed as "Gallons per Minute" (GPM).

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

Translating Ratings into Actual Costs

Let’s break it down with a simple 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. Translate gallons into 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 to kWh (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.

Comparing Tank and Tankless Water Heaters for Efficiency

- Tank Heaters

• Always keep a reservoir of hot water.

• Standby losses often rise in cold climates.

• Recovery rate restricts simultaneous use, risking hot‑water depletion when multiple appliances run.

- Tankless 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.