Here’s a simple test: put your hand on the side of your water heater. If the outside of the tank feels warm, it’s losing heat into the room, and you’re paying to keep reheating that water. A water heater insulation blanket (sometimes called a jacket) is one of the least expensive and easiest ways to cut that standby heat loss.
But it’s not right for every heater, and it has to be installed correctly, especially on gas models. Here’s what to know.
Is a water heater insulation blanket worth it?
A tank water heater keeps a large volume of water hot around the clock. When the tank is poorly insulated, heat escapes through the walls and the heater cycles on more often to make up for it. That’s called standby loss.
A blanket can be worth it if:
- The tank is warm to the touch
- It’s an older model with less factory insulation
- It sits in an unheated or chilly space like an unfinished basement, garage or crawlspace
It’s usually not worth it, or not allowed, if:
- The tank is newer and well insulated (it feels cool on the outside)
- The manufacturer’s label or manual says not to use an external blanket
- It’s a tankless water heater (they don’t store hot water, so there’s nothing to insulate)
Always check the warning labels on your heater before you buy anything.
Choosing the right blanket
Home improvement stores carry pre-cut water heater blankets, typically one and a half to three inches thick, that fit most standard tank sizes. Look for:
- A kit sized for your tank’s capacity (40 gallon, 50 gallon and so on)
- A higher R-value for more insulation
- Fiberglass insulation with a vinyl or foil facing, plus tape included
Measure the height and circumference of your tank before shopping.
How to install a water heater insulation blanket, step by step
You’ll need the blanket kit, a utility knife, a tape measure, a marker and gloves (fiberglass can irritate skin).
1. Turn off the heater
- Electric: Switch off the breaker.
- Gas: Turn the gas control to “Pilot” so the burner doesn’t fire while you work.
2. Wrap the tank
Wrap the blanket around the tank and hold it in place with a couple of pieces of tape. On an electric heater, the blanket can usually cover the top. On a gas heater, it should cover only the sides.
3. Mark the openings
With a marker, outline everything that must stay uncovered:
- Warning labels and the rating plate
- The temperature and pressure (T&P) relief valve and its discharge pipe
- The drain valve at the bottom
- Electric: the access panels for the upper and lower thermostats and elements
- Gas: the gas control valve, burner access panel and pilot area
4. Cut the openings
Take the blanket off and cut out the marked areas with a utility knife, leaving a little extra room around each one.
5. Install and tape
Wrap the blanket back around the tank, line up the openings, and tape the seams securely. Trim off any excess.
6. Gas heaters: keep the top and bottom clear
Leave the top of the tank uncovered, along with the flue and draft hood. Keep the blanket at least a couple of inches above the floor so it doesn’t block the combustion air intake at the bottom. Follow the clearances in both the blanket instructions and your heater’s manual.
7. Restore power or gas
Turn the breaker back on, or set the gas control back to “On.” Check over the next few days that the blanket hasn’t slipped over any controls.
Other ways to cut water heating costs
- Insulate the pipes. Foam sleeves on the first several feet of hot and cold pipes from the heater keep more heat in.
- Lower the thermostat. About 120°F works for most households, saves energy and reduces scald risk. If you’ve added a blanket to an electric heater, the U.S. Department of Energy advises not to set the thermostat above 130°F, since the blanket can cause wiring to overheat.
- Flush the tank. Sediment insulates water from the heat source. See how to flush a water heater.
- Fix drips. A dripping hot water faucet wastes both water and energy.
Seasonal tips for Philadelphia and South Jersey
Our winters are cold enough that basements and garages often sit in the 40s or 50s for months. A water heater in one of those spaces loses heat much faster than one in a heated utility closet, so the fall is a smart time to add a blanket and pipe insulation. Pipe sleeves also give some protection to lines that run along cold exterior walls during January cold snaps.
Safety notes
- Wear gloves, long sleeves and a dust mask when handling fiberglass.
- Never cover controls, valves, labels or access panels.
- On gas heaters, blocking the flue or air supply can cause carbon monoxide problems. Keep a CO alarm near any fuel-burning appliance.
- If you’re unsure, don’t guess. Follow the manufacturer’s instructions or ask a pro.
When to call a pro
A blanket is a quick DIY job, but some water heater situations need a professional. Call a pro if:
- You have a gas heater and aren’t sure about clearances
- The tank is leaking, rusty or making loud noises
- Pipes around the heater are corroded or leaking
- The heater is in a cold, damp or cramped space that needs work
We handle plumbing repairs around water heaters, pipe insulation and leak fixes, and can help make an unfinished basement a better home for your mechanicals. Add it to your maintenance routine, or request a quote today.
