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Not that we need to remind you, but heating a home is expensive. According to the U.S. Department of Energy, heating costs are responsible for around 30% of the typical home utility bill—more than any other “system” in the home.

While there are many ways to cut these costs (like using a programmable thermostat or simply wearing a sweater in lieu of cranking up the heat), one very practical step you can take is to outfit your home with an efficient heating system. Even if it requires an upfront investment, you’ll save money over time because the more efficient a heating system is, the less energy it needs to operate, and this can translate into lower heating bills.

It helps, of course, to know what defines “efficient” so that when you go in search of one—or when you are trying to determine whether your existing system is efficient—you’ll know what to look for.

A heat pump’s effectiveness is directly affected by weather conditions. In moderate climates, heat pumps are far more efficient than a furnace. In very cold climates the furnace is more efficient (although heat pumps are becoming contenders quickly).

In general, the most important piece of information is the system’s annual fuel utilization efficiency rating, or AFUE for short. This measurement, which is a percentage rate, tells you how much of the energy (usually, in the form of electricity or natural gas) that the system consumes is going directly toward heating your home versus how much is going to waste. In other words, it lets you know how much energy the system is converting into usable heat.

An AFUE of 90%, for example, indicates a high rate of efficiency—a system with this rating is putting all but 10% of its energy to good use. Currently, the DOE requires a minimum AFUE of 80%, but a lot of modern heating systems exceed the minimum (some rate as high as 98.5%).

The least efficient system? Basically, anything manufactured before 1992, before there were any AFUE standards. This means that if you live in a 30-plus year-old home and haven’t upgraded the heating system since then (or ever), you are probably wasting a lot of energy and money.

How much energy? That depends on so many individual factors, but to give you an idea of the difference between old furnaces and newer ones, the DOE reports that “upgrading your furnace or boiler from 56% to 90% efficiency in an average cold-climate house will save 1.5 tons of carbon dioxide emissions each year if you heat with natural gas.”

That’s a lot of CO2.

It can also reduce your heating bill by as much as 50%, says the DOE.

Practically speaking, though, finding a heating system with a high AFUE rating is only one part of finding the most efficient heating system for your home. You also have to find one that is compatible with your home’s energy source. Some homes are outfitted for electric heating systems only; others are set up for natural gas.

Natural gas, by definition, is more efficient overall than electricity, so if that is what you are going for—and your home isn’t already natural-gas compatible—check with your local gas company to find out whether conversion to natural gas is possible. If it is, or if you are already set up with your energy source of choice, the next step is to decide which of the three main types of heating systems is best for your home.

In general, furnaces are the most efficient of the heating systems, especially if you have natural gas. They work by heating air with a component called a heat exchanger and pushing it into the home through a duct system, using a fan (often referred to as a blower). Along with the fact that they have high-efficiency ratings, one of the biggest advantages of furnaces is the relative affordability.

Most folks can expect to pay between $2,000 and $7,000 for a new furnace (natural gas furnaces, as opposed to ones that run on electricity, are on the higher side). The downside of this choice? Thanks to the fan, furnaces are often loud.

A heat pump is an air conditioning and heating unit all in one (the fact that it is dual purpose makes it efficient in its own way). When it is hot outside, the unit grabs air from inside your home, removes the heat from it with a refrigerant and pumps it back into the home as cool air. During winter, it takes air from inside and adds heat to it before sending it back indoors to warm up your space. Outdoor air is never brought in through the heat pump.

Benefits include excellent air filtration and lack of noise (unlike furnaces, they are quiet). On average, heat pumps cost around $5,600, with some costing as much as $20,000 depending on the type you get (heat pumps come in three varieties—air-source, split-duct and geothermal). Will a heat pump reduce your energy expenses? Maybe, or maybe not. They may actually raise your electric bill just as much as they lower your gas bill, so it could be a toss-up.

In terms of measuring efficiency, heat pumps don’t go by the AFUE. Instead, their efficiency is based on the Heating Seasonal Performance Factor (for heating mode) and the Seasonal Energy Efficiency Ratio (for cooling mode). To avoid confusion, your best bet is to just look for a heat pump that is Energy Star certified (this will help make sure you are getting one that checks off all the right boxes).

Believe it or not, boilers are still a thing. As the name suggests, a boiler is a system that heats up water in a tank and uses that water to warm your home, pumping water from the boiler’s tank through a series of pipes to individual radiators. The radiators then distribute heat around various rooms and spaces.

Natural gas boilers are as efficient, if not more so, than furnaces (some have AFUE ratings of up to 100). Electric boilers are uncommon in homes (at least in the U.S), and so are boilers that run on oil, even though you can still get them. In terms of cons, because of their shape (tall and cylindrical) boilers take up more space than the average furnace. They are also quite expensive (up to $10,000), and if anything goes wrong, the repairs can get pretty pricey, too.

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Dawn Weinberger is a freelance writer in Portland, Oregon who has contributed to numerous publications and websites over the past 20 years, including RD.com, Glamour, Women's Health, Entrepreneur, and many others. Dawn has a BA in journalism from Western Washington University and is a member of the American Society of Journalists and Authors. She writes about everything from health and medicine to home improvement and business.

Samantha is an editor who covers all topics home-related including home improvement and repair. She edited home repair and design content at websites like The Spruce and HomeAdvisor. She also has hosted videos on DIY home tips and solutions and launched multiple home improvement review boards staffed with licensed pros.