AFUE: The unknowns - what you need to know about AFUE ratings and their inaccuracy (Oil Boilers)

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AFUE and Oil Boiler Facts

AFUE Ratings Are Not Accurate
Boiler rating or boiler efficiency is typically measured by Annual Fuel Utilization Efficiency (AFUE). AFUE ratings are not accurate.

Determining The Real Efficiency (Oil Boilers)
To determine the real oil boiler efficiency, use our interactive illustration by placing your mouse over the specific boiler area. [ View Gas Boiler Version ]

Efficiency Indicator	Typical Tankless Coil Boiler	"High Efficiency" Cast Iron Boiler	System 2000
AFUE Rating	82% - 87%	86% - 87%	Up to 87%
Real Efficiency	56% - 59%	56% - 62%	Up to 85%
Draft Regulator	YES	YES	NO
Jacket Insulation	¾" to 1" sides & top	¾" to 1"	Up to 4"
Base Insulation	No - boiler sits directly on floor	No	YES insulated plus boiler mounting stand
Outside Air for Combustion	No	Optional	YES
Energy Saving Control	Not applicable or not an option	Additional Cost and requires trial and error adjustments	Energy Manager for combined heat and hot water standard on all systems. More efficient than indoor/outdoor reset controls
Integrated Hot Water System	Coil in boiler for hot water or electric	Coil in boiler (tankless coil) or indirect tank	High performance hot water storage tank with integrated control

When the government created AFUE (Annual Fuel Utilization Efficiency) ratings, they had a good plan. However, AFUE ratings don’t help consumers make educated decisions about a hot water heating system’s efficiency because it only measures some chimney related losses. It’s like saying highway driving is the miles per gallon you’ll get all year when you know you’ll be doing most of your driving around town.

It’s time the heating industry had an accurate way to measure efficiency.

AFUE remains a misleading indicator that should be improved with an index that truly measures a hot water system’s efficiency. The heating industry needs it. The homeowner deserves it. Once you’re able to accurately compare different heating system’s efficiency,

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