Choosing the best hot water heaters comes down to a variety of factors including your water usage, how much you want to pay upfront, and finally the energy efficiency. The energy efficiency comparisons vary across different types of models – a tankless water heater, for example, is more efficient than a tanked heater – but you might also need to compare the energy efficiency between similar models to ensure you get the best unit for your needs.

There are a couple of key water heater efficiency metrics that can help you choose between otherwise similar units. The ratings should appear in an easy to locate information box on the box and the unit itself plus in the manufacturer's information. 

First-Hour Rating

First-hour rating refers to the maximum amount of water that could be available at the busy time of the day or the hour of highest usage. In a tanked water heater, the amount is typically the amount that can fit in the tank unless the unit can very quickly heat up incoming water to lengthen the supply. A larger tank can help but the recovery rate, or how quickly the tank can produce new hot water, has a larger impact on the first-hour rating and the unit's overall energy efficiency.

Choosing a model with the highest first-hour rating can ensure you will never run out of water at a busy time. But going that route only makes sense if you have multiple people in your household who all tend to use water at the same time. If you live alone, or use water at vastly different times of the day, prioritizing first-hour rating could leave you with an oversized unit and actually cost you energy efficiency.

Energy Factor

The energy factor is a measurement that represents the overall energy efficiency of the water heater. A higher energy factor means the water heater is more energy efficient. The measurement takes into account the recovery speed of the heater and any potential losses that happen when the water sits around in a tank waiting to be used, called a standby loss, or circulates through the tank and the pipes, appropriately called a cycling loss.

You might think that simply picking the water heater with the highest energy factor would automatically provide you with the best buy. But you need to also take your fuel or electricity costs into account. An otherwise more efficient water heater that uses gas rather than electric-only, for example, could end up costing more to operate due to the fuel costs.

Energy efficient units also tend to cost more upfront so you need to factor into account how much energy savings you will receive per year and how long it will take that heater to "pay for itself" with the energy savings.

Need more information? Contact a plumbing supplies company.