Chapter 01Records · System
Water heater size and age record
Photograph the yellow EnergyGuide label and the data plate, then copy the maker, model, serial number, tank size and first hour rating onto one page. Find the install date in the invoice, the inspection report or a permit; if there is none, read the date made from the serial number. Add the 13-year average-life mark from the PNNL sizing page as a planning date. Then add up your busiest hour of hot water and check that the first hour rating covers it. Anything done to the heater itself goes to a licensed plumber, the maker or your landlord.
Source: 16 CFR 305.17, EnergyGuide label content, checked October 20, 2026; City of Palo Alto, Check Your Water Heater's Age, checked October 20, 2026; PNNL Building America, DHW First Hour Rating, checked October 19, 2026.
- Average life on the PNNL sizing page, a planning date only13 years PNNL Building America, DHW First Hour Rating, October 19, 2026
- Hot water for one shower on the AHRI worksheet20 gal PNNL Building America, DHW First Hour Rating, October 19, 2026
- Very small, low, medium and high on the yellow label4 bands 16 CFR 305.17, EnergyGuide label content, October 20, 2026
Do it, skip it or get help
Read, size and log it yourself
Everything here is read from the outside of the heater or from paper. You need a phone, a flashlight, the estimator and the record page.
Skip the sizing if there's no heater in your unit
In an apartment where the building supplies hot water, there's nothing to size. Keep the page for the times the hot water runs out and send those notes to the manager.
Any work on the heater goes to a licensed plumber
Draining, flushing, the thermostat, valves, venting, relighting and replacing all belong to a licensed plumber, the maker's manual or the landlord. This page holds the numbers and dates you hand them.
The steps, in order
Photograph both labels
Take a clear photo of the yellow EnergyGuide label and of the maker's data plate, standing where you can see them. If a label is out of reach, write "label not reachable" and ask at the next visit.
Have ready: A phone and a flashlight for a dark closet
Copy the four lines
Maker, model number, serial number, and the tank size with the first hour rating. Federal rules make a tank heater's label show capacity both ways. A tankless label shows a gallons per minute band instead.
Have ready: The photos and the record page
Source: 16 CFR 305.17, EnergyGuide label content, checked October 20, 2026; City of Palo Alto, Check Your Water Heater's Age, checked October 20, 2026.
Write the exact rating, not only the band
The label puts the first hour rating in a band: very small under 18 gallons, low 18 to 50.9, medium 51 to 74.9, high 75 or more. Copy the number itself, because the band is too rough to size by.
Have ready: The label photo
Source: 16 CFR 305.17, EnergyGuide label content, checked October 20, 2026.
Find the install date
Check the installer's invoice, the home inspection report and the city's permit record. If none has it, read the date made from the serial number and write "made, not installed" beside it.
Have ready: The house binder, your email and the serial number
Source: City of Palo Alto, Check Your Water Heater's Age, checked October 20, 2026.
Add the 13-year planning date
The PNNL sizing page uses an average life of 13 years. Write the install date plus 13 years on the page. It's a date for the binder, not a verdict on your heater.
Have ready: The install date
Source: PNNL Building America, DHW First Hour Rating, checked October 19, 2026.
Check the rating against your busiest hour
List what runs in your busiest hour and let the estimator add it up: about 20 gallons a shower, 14 a dishwasher load, 32 a clothes washer load. The first hour rating should be equal to or greater than that total.
Have ready: One real morning or evening, counted use by use
Source: PNNL Building America, DHW First Hour Rating, checked October 19, 2026.
Put the help numbers on the page
Write the installer or plumber, the maker's customer line and, if you rent, the landlord. When the hot water stops, the numbers and the model are on one sheet.
Have ready: The invoice and the maker's website
Note each time the hot water runs out
Write the date, the time and what was running. A few of those lines tell the plumber or landlord far more than "it runs out sometimes".
Have ready: The record page by the closet
Write a line after every visit
Date, who came, what they did or said, and any next date they gave you. If the heater is replaced, start a new page and keep the old one.
Have ready: The visits table on the record
Print the working copy
One page, black and white, US Letter. Tick the boxes and write the dates in.
- Yellow label photographed
- Data plate photographed
- Maker and model copied
- Serial copied, read twice
- Tank size and first hour rating copied
What goes wrong
The heater gets sized by its tank
Two heaters with the same tank can rate differently, because ENERGY STAR says the first hour rating depends on both the storage volume and how fast the heater recovers. Size by the first hour rating instead.
Source: ENERGY STAR Residential Water Heaters spec, Version 5.0, checked October 20, 2026.
Nobody knows when it went in
Without the date, "it's fairly new" can mean anything. The serial number at least gives the date made, and the heater can't have gone in before that. The City of Palo Alto's page shows how to read it for three big brands.
Source: City of Palo Alto, Check Your Water Heater's Age, checked October 20, 2026.
Only the band gets written down
Medium covers everything from 51 to 74.9 gallons. A heater at 52 and one at 74 look the same on a page that says "medium", and the busiest hour check needs the number.
Source: 16 CFR 305.17, EnergyGuide label content, checked October 20, 2026.
The serial number is copied wrong
The letters O and Q and the digit zero look alike on a small plate. With one wrong character, the maker's lookup won't match. Copy from the photo and read it twice.
Running out never gets a date
"We run out of hot water sometimes" gives the plumber nothing to work with. The date, the time and what was running let them see the pattern at the first visit.
When the steps change
Tankless heater
There's no tank and no first hour rating. The label shows a gallons per minute band (very small 0 to 1.6, low 1.7 to 2.7, medium 2.8 to 3.9, high 4.0 or more), and the estimator's tankless check adds up the taps you run at the same moment.
Source: 16 CFR 305.17, EnergyGuide label content, checked October 20, 2026; PNNL Building America, DHW Instantaneous Sizing, checked October 19, 2026.
Renting
Fill in the record and the busiest hour the same way. The heater and every visit belong to the landlord, so send the page and any ran-out notes in writing and write down the date you sent them.
A deep tub or a growing household
A bath counts the same as a shower on the worksheet, 20 gallons. If a soaking tub or a new person is coming, run the estimator for that future hour too and keep both totals on the page.
Source: PNNL Building America, DHW First Hour Rating, checked October 19, 2026.
Tips and tricks
- Tip 01
Tape a copy inside the closet door
Keep one copy in the binder and one where the heater is. A plumber can read the model and the install date without asking you.
- Tip 02
Copy at the table, not in the closet
Zoom into the label photos at a table with good light. It's quicker, and you're less likely to misread the serial.
- Tip 03
Write where each date came from
"Invoice", "inspection report", "permit" or "serial, made not installed". Whoever reads the page later knows how far to trust it.
- Tip 04
Count a real morning
Run the busiest hour from what actually happened on a weekday, not from a guess. Who showered, what ran in the kitchen, whether the washer was on.
- Tip 05
Keep the old page when the heater changes
Start a fresh record for the new heater and file the old one behind it. Its install date and visit lines show how the last one went.
What we would do
Photograph the labels today, fill the page this week
Two photos take a minute. Then print the free page, copy the four lines, chase down the install date and run one real busiest hour through the estimator. File it in the binder and tape a copy by the heater.
The tools and guides in this system
Chapter 01Water heater capacity estimatorAdd up your busiest hour of hot water, check it against the first hour rating on the EnergyGuide label, and print a record of your heater.Open the tool
Chapter 01Appliance and warranty logRecord each appliance's model number, serial number and purchase date, see which warranty ends next, and print a one-page log for the drawer.Open the tool
Chapter 01Home service logTurn the last visit for your heating, cooling, chimney and septic service into the next due date and a book-by date, then print a log of who to call.Open the tool
Know-howReading the water heater label and data plateWhat the yellow EnergyGuide label and the data plate on a water heater tell you: tank size, first hour rating, band, model and serial, and what to copy down.Read the guide
Practical noteHow old is my water heater? Finding the install dateFind a water heater's age from the paperwork or the date code in its serial number (Rheem, A. O. Smith, Bradford White), then log it with the 13-year mark.Read the guide- Chapter 01All records toolsPrintable home records with a calculator behind each one: appliance and warranty log, HVAC filter sizes and change dates.Open the chapter
Questions
What should a water heater record include?
The maker, model and serial number from the data plate, the tank size and first hour rating from the yellow label, the install date and where it came from, the 13-year planning date, your busiest hour total, the help numbers, and a line for every visit.
Source: 16 CFR 305.17, EnergyGuide label content, checked October 20, 2026; PNNL Building America, DHW First Hour Rating, checked October 19, 2026.
How do I find out how old my water heater is?
Look for the install date on the invoice, the inspection report or a permit first. If there's nothing, read the serial number: Rheem puts the month and year first, current A. O. Smith serials start with the year and week, and Bradford White uses a year letter and a month letter.
Source: City of Palo Alto, Check Your Water Heater's Age, checked October 20, 2026.
Is the tank size the same as the first hour rating?
No. The tank size is what the tank holds. The first hour rating is how much hot water it can deliver in an hour starting full, and ENERGY STAR says it depends on the tank and on how fast the heater recovers. The label shows both.
Source: ENERGY STAR Residential Water Heaters spec, Version 5.0, checked October 20, 2026; 16 CFR 305.17, EnergyGuide label content, checked October 20, 2026.
What size water heater does a family of four need?
It depends on their busiest hour. Two showers, breakfast cooking, washing up at the sink and a shave come to 59 gallons on the worksheet, so that family wants a first hour rating of 59 or more.
Source: PNNL Building America, DHW First Hour Rating, checked October 19, 2026.
Does my water heater need replacing at 13 years?
This page can't tell you. Thirteen years is the average life the PNNL page uses, and it goes on the record as a planning date. Whether to repair or replace is a question for a licensed plumber or your landlord.
Source: PNNL Building America, DHW First Hour Rating, checked October 19, 2026.
The primary source
DHW First Hour Rating (RED Calc tool), Pacific Northwest National Laboratory, Building America Solution Center (U.S. Department of Energy). Checked October 19, 2026.
The steps on this page follow this source. Other figures cite their own source where they appear.
Other sources on this page
- 16 CFR § 305.17: Television labeling and water heater label content (EnergyGuide), Federal Trade Commission, 16 CFR 305.17 (Energy Labeling Rule), via Cornell LII. Checked October 20, 2026.
- Check Your Water Heater's Age, City of Palo Alto Utilities. Checked October 20, 2026.
- ENERGY STAR Program Requirements, Product Specification for Residential Water Heaters, Final Draft Version 5.0, ENERGY STAR (U.S. Environmental Protection Agency). Checked October 20, 2026.
- DHW Instantaneous Sizing (RED Calc tool), Pacific Northwest National Laboratory, Building America Solution Center (U.S. Department of Energy). Checked October 19, 2026.
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