One homeowner took to the internet to ask whether lowering a water heater's tank temperature twenty degrees would be a worthwhile way to cut energy use, and the response was swift.
The idea may trim costs, but it could also introduce health concerns and shorten how long hot water lasts.
Here's what to know
The discussion started when a homeowner asked Reddit's r/HomeImprovement community whether advice from an "environment expert" made practical sense.
The suggestion was to keep a tank at 100-104 degrees Fahrenheit rather than 140 so people would not need to add cold water at the tap. "That sounds very reasonable, and I can't recall when we will need piping hot water in the house," the poster wrote. "I want to have a sanity check, however. Is this actually good advice in practice?"
Commenters pushed back for two main reasons.
Safety came up first. Several users said water stored below 120 F may allow Legionella to grow, while temperatures above 140 increase scalding risk.
They also argued that hotter stored water gives you more usable hot water because it is diluted with cold water at the fixture. "If I'm mixing half cold and half hot water at the showerhead, then my hot water lasts twice as long," one commenter wrote.
Even the savings described in the thread were limited. Using one commenter's example, a modern unit that costs $20-$30 per month to operate might save only a couple of dollars by moving from 140 to 120 degrees, a change they estimated would reduce water-heating by 10-15%.
Save $10,000 on solar panels without even sharing your phone number Want to go solar but not sure who to trust? EnergySage has your back with free and transparent quotes from fully vetted providers in your area. To get started, just answer a few questions about your home — no phone number required. Within a day or two, EnergySage will email you the best options for your needs, and their expert advisers can help you compare quotes and pick a winner. Solar panels can save you more than $50k over their 25-year lifespan, and EnergySage can help you save as much as $10k on installation. Which begs the question — isn't that worth an email or two? |
More background
In this case, Redditors argued that turning the tank all the way down to shower temperature could reduce safety while also causing the household to run out of hot water more quickly.
"You don't want the water heater anything near 100 Celcius (boiling point)," one commenter said. "That is extremely dangerously hot. But you also don't want it just warm, as that could allow Legionella bacteria to flourish."
A few people added nuance by pointing to modern heat pump-based systems, which can behave differently. Some noted that these setups may run at lower temperatures during normal use but still perform weekly cycles above 140 F (60 C) to deal with bacteria.
The safest and most efficient setup may depend on the type of water heater, not just the number on the dial.
A conventional tank should not be set to shower temperature. A safer option is to check manufacturer guidance, verify tap temperatures, and consider only a modest adjustment within a recommended range. If scalding is a concern, mixing valves and anti-scald fixtures can deliver safer water at the tap without storing the entire tank at too low a temperature.
For people who want to cut bills more meaningfully, replacing an aging system may be a stronger move than trying to squeeze a few dollars out of a thermostat tweak. Check out Cala and its smart heat pump water heaters. Its units heat water only when you need it and can seriously reduce your water heating costs.
Get TCD's free newsletters for easy tips, smart advice, and a chance to earn $5,000 toward home upgrades. To see more stories like this one, change your Google preferences here.
