Is a water heater insulation blanket worth it? The touch test, DOE's 7% to 16%, the R-10 target, and what the makers say to leave uncovered

Do not buy a blanket until you have touched the tank and read the manual: a cool jacket saves nothing, and on a gas heater a blanket fitted wrong can block the combustion air.

Does your tank need a blanket at all?

Put a hand on the side of the tank. DOE’s 2017 Energy Saver Guide says that if the tank is warm to the touch, insulating it can save 7% to 16% of annual water heating cost. If it is not warm, the factory insulation is already holding the heat in.

Standby loss is the heat a tank loses to the room between draws, and newer tanks are built against a federal limit on it. A. O. Smith’s Technical Bulletin 60 says blankets “are not necessary with A. O. Smith products” because the heater “meets or exceeds the National Appliance Energy Conservation Act standards” for standby loss; a residential electric Use & Care Manual hosted on files.myrheem.com says the same of its electric tanks.

The older the tank, the likelier it is warm; the water heater age guide reads the age off the serial number.

What do the DOE numbers mean?

The 2017 Energy Saver Guide prints the savings: 7% to 16% of water heating cost for the tank blanket and “an additional 3%–4% per year” for the pipes. DOE’s current Savings Project pages for both jobs returned 404 at the last check, so no newer DOE percentage is printed here.

The June 2024 Weatherization Job Aids 23-1 (electric) and 23-2 (gas) print the target: the tank “is insulated to achieve overall tank R-value of R-10,” after checking the data plate for the existing level and confirming the maker does not prohibit more. R-10 is the total, factory foam included; no opened document prints a modern tank’s factory R-value.

Job Aid 23-3 covers the pipes: a minimum of R-3 for at least 6 ft from the heater on the hot and the cold line, seams taped, at least 6 in back from a draft diverter or single wall vent pipe.

What does the payback look like?

No opened DOE page prints a dollar saving, so this is the formula with your own inputs. Annual saving = annual water heating cost x DOE’s 7% to 16%, for a tank that passes the touch test. An electric tank’s cost is its annual kilowatt-hours times the rate: EIA’s Table 5.6.A puts the US residential average at 18.16 cents per kWh for August 2026 (preliminary), up from 17.57 cents in August 2025. A household spending $400 a year on hot water would see $28 to $64 a year at DOE’s range; the blanket’s price on the live card sets the payback.

What do the makers say to leave uncovered?

A gas tank draws combustion air in at the bottom and vents through a draft hood on top, so the blanket’s two biggest mistakes are at the ends. A. O. Smith’s Bulletin 60 says not to insulate the top, “as this will interfere with safe operation of the draft hood,” to keep the insulation 2 in off the floor, and to inspect it often for sagging, because a blocked air path “can restrict the air flow required for proper combustion,” with fire and asphyxiation as the consequence.

DOE’s Job Aid 23-2 lets an installer tape insulation to the top of a gas heater 6 in clear of the draft diverter; A. O. Smith says not to insulate the top at all. The maker’s manual controls the tank you own.

On an electric tank the top stays bare for the electrical junction box, and Job Aid 23-1 adds cutouts for every access panel and safety feature, with plastic ties not cinched tight enough to compress the insulation.

Warranty is where the makers part. Bulletin 60 says a blanket “will not void your warranty,” contrary to the exclusion in its own manual; the electric manual says its warranty does not cover damage caused by unauthorized energy saving devices. Neither transfers to another brand.

Should you wrap the pipes first?

Yes. Pipe wrap is the cheaper job and DOE’s 2017 guide credits it with 3% to 4% a year. The Duck Brand covers on this page fit 3/4 in pipe only and print no R-value in the listing, so check the package for R-3 and match any other diameter on the pipe insulation sizing page.

What should you do first?

1. Touch the side of the tank: warm means DOE’s 7% to 16% is on the table, cool means skip the blanket.
2. Read the data plate and the manual’s insulation section for the existing R-value, any prohibition and the warranty wording.
3. Wrap the first 6 ft of hot and cold pipe to R-3 (Job Aid 23-3), 6 in clear of any draft diverter.
4. Check the thermostat is at 120 F: the temperature setting guide covers that saving.
5. Fit the blanket only on a warm tank the maker permits, with the top, controls, access panels, T&P valve, labels and the 2 in floor gap bare, and inspect it for sagging.

A tank that still runs out of hot water is a recovery problem, not an insulation one: the water heater recovery time calculator works it out.

Frequently asked questions

Sources

1. DOE Energy Saver Guide 2017 (EPUB), chapter 4 Water Heating (government or regulatory source)
2. DOE Weatherization Job Aid 23-1: Insulate an Electric Domestic Water Heater (June 2024, PDF) (government or regulatory source)
3. DOE Weatherization Job Aid 23-2: Insulate a Gas Domestic Water Heater (June 2024, PDF) (government or regulatory source)
4. DOE Weatherization Job Aid 23-3: Insulate Domestic Hot Water Pipes (June 2024, PDF) (government or regulatory source)
5. A. O. Smith Technical Bulletin 60: Insulation Blankets (manufacturer or vendor document)
6. Residential electric water heater Use & Care Manual with electronic control, Insulation Blankets section (PDF hosted on files.myrheem.com) (manufacturer or vendor document)
7. EIA Electric Power Monthly, Table 5.6.A, Average Price of Electricity to Ultimate Customers by End-Use Sector (released 23 October 2026) (government or regulatory source)