The 9 Best Heat Diffusers

The HIC Simmer Plate (about $6) is a light, perforated disc that sits between the burner and the pot to spread the heat and soften hot spots. The 8.25-inch plate is made of stainless and chrome-plated steel and weighs 6.4 ounces. Its long handle has a plastic grip that stays cool and comes off for storage. HIC, short for Harold Import Company, says it works on gas, electric and glass stovetops, steadies small pots such as moka makers and butter warmers, and can go in the dishwasher. It suits rice, oatmeal, milk and sauces that tend to catch on the bottom. The thin steel stores little heat, so it evens things out less than a heavy plate, it isn't sold for induction, and the glass-top approval rests on the maker's word.

The Cooks Innovations SimmerMat (about $35) is a thin octagon of enameled steel, about 7 7/8 inches across and a quarter-inch thick, with raised dimples on one face. Steel is magnetic, so the mat heats on an induction cooktop, and the maker approves it for gas, electric coil, glass, ceramic, halogen and induction tops, plus grills and marine stoves. That makes it one of the few plates that lets glass, clay or aluminum pots simmer on induction. The maker shows which side should face up on each kind of stove and says to keep the heat low. It weighs about 7 ounces and can go in the dishwasher. There's no handle, so lift it with an oven mitt, and its size suits small and medium pots better than wide pans.

The Ilsa Cast Iron Diffuser (about $35) is a heavy enameled plate that soaks up heat and passes it on slowly and evenly, so a pot of beans or ragu can hold a bare simmer with less stirring. It's sold as an 8.25-inch plate, though the product photos put it closer to 8.7 inches across, with raised ribs around a hole in the center. A stainless steel handle clips on and comes off. Ilsa, an Italian cookware maker, backs it with a one-year warranty. The center hole means it does its best work over gas. It isn't dishwasher-safe, so wash it by hand and dry it well. A retailer selling Ilsa's smaller 7-inch plate warns against glass cooktops because cast iron can scratch them, so keep this one off glass too.

The Nordic Ware Heat Tamer (about $22) is a plain 8-inch disc of aluminized steel, made in the United States, that gives a pot a flat, even base on an electric coil or a gas grate. It's a handy fix for coil burners, whose spiral can leave a scorched ring on a thin pan bottom, and for small pots that wobble on wide grates. The plate weighs 1.4 pounds, wipes clean and comes with a five-year warranty. Nordic Ware states plainly that it isn't for ceramic or glass cooktops, so skip it if your range has a smooth top. It isn't meant for induction either, and with no handle you'll need a mitt to move it while it's hot.

The Heat Equalizer Cast Iron (about $29) plate is a thick 9.25-inch disc whose face is covered in more than 480 small raised bumps, which the maker says collect and spread the heat. At 0.4 inch thick and about 3 pounds, it stores a lot of warmth, which suits stockpots, Dutch ovens and clay pots that need a slow, steady simmer. There's no handle. The maker offers a 12-month warranty and a 30-day return window, and it warns never to leave the plate on a lit burner without a pot on it. Its compatibility claims are muddled: the product name says gas and induction, while the description excludes induction. Treat it as a gas plate unless the maker confirms your stove. Its energy-saving claims come without published tests.

The Aunt Shannon's Cast Iron Set (about $34) gives you two enameled cast-iron plates, 8.25 and 6.75 inches across, so the smaller one can go under a butter warmer or moka pot while the larger one handles a saucepan. Both have wavy, scalloped edges, short raised ribs and stainless steel handles that come off. The pair weighs about 3.9 pounds. The seller says they work on gas and electric stoves and lists glass cooktops as suitable, but rules out induction. That glass-top claim runs against appliance makers' general caution about cast iron on glass, so check your range manual first. This is a small seller, and there's little information about the plates beyond the product page.

The Kuhn Rikon Energy Saver (about $74) is an 11-inch aluminum disc with a nonstick coating, made for gas stoves only. The Swiss cookware maker designed it to shield fine stainless pans and its own pressure cookers from a direct flame, and its width lets it sit under large skillets and stockpots without the pan hanging past the edge. Aluminum moves heat quickly, so it spreads a flame across a wide pan bottom fast, and the coating wipes clean. The disc is about a quarter-inch thick and weighs 2.2 pounds. The price is high for a plain plate, there's no handle, and it isn't meant for electric, glass or induction cooktops. The maker's energy-saving claim comes without published test data.

The Runzi Induction Adapter (about $18) is a 7.5-inch disc for induction cooktops, which only heat pans a magnet will stick to. The disc warms up on the induction zone and passes that heat to a glass, aluminum, copper or ceramic pot on top, so a moka pot or a favorite saucepan can still be used. The seller says it has three layers, with aluminum between two sheets of stainless steel, plus three dimples on top and a handle that comes off. It weighs 650 grams, and the seller lists a lifetime replacement warranty. An adapter like this cooks slowly and wastes energy, since the cooktop heats a plate instead of the pan, and it gets very hot. Owner feedback is mixed, and its specs come from the seller alone.

The Teabloom Diffuser Trivets (about $11) are a pair of bent-wire rings, each about 4 inches across, that hold a glass teapot or coffee pot just above an exposed electric coil. Teabloom, which sells glass teapots, makes them so a stovetop-safe glass pot doesn't sit right on a glowing coil, where uneven heat can stress the glass. The open wire also lowers the heat under small metal pots for a gentle simmer. The packet prints placement and safety steps, including never letting a pot boil dry. They're designed for exposed coil burners, not gas grates or smooth glass cooktops, and the small size suits only small pots. The product dates from 2024, so owner feedback is still limited.