To understand real boiler efficiency, go beyond AFUE.

U.S Department of Energy lab results1: AFUE is inaccurate, especially for boilers that make hot water.


This study shows Energy Kinetics design is more efficient than the 95 AFUE modulating condensing boiler and all other condensing and non-condensing boilers and systems tested.

Energy Kinetics High Efficiency Gas and Oil Boilers achieve best annual efficiency in Department of Energy Lab Study1 and achieve Energy Star Most Efficient2

The above chart shows a department of energy laboratory study1 for annual efficiency of heat and hot water systems. AFUE much more closely represents peak efficiency, and the energy wasted when the boiler shuts off really cuts down the annual efficiency. Comparing the 83.5% AFUE tankless coil boiler at right, System 2000 will cut fuel bills by over 43%…although there is only a 4% difference in AFUE ratings. This means the tankless coil boiler will burn 77% more energy than System 2000.

All of our high efficiency boilers, including Accel CS and the non-condensing 90+ Resolute and System 2000 are more efficient than the other 95% AFUE modulating condensing boiler and all boilers in the study. Notice the very small difference between AFUE and annual efficiency for all of Energy Kinetics high efficiency oil boilers and high efficiency gas boilers. Compare that to losses for all other boilers which will have 14% to 73% higher fuel bills than their AFUE ratings indicate.

How is this possible? Energy Kinetics pioneered low mass technology with thermal purge, and has perfected it over 35 years. Our design heats up in just a few minutes, heats your home or hot water, and then runs a thermal purge that puts energy remaining in the boiler to work heating your home or hot water. There’s no energy left wasted in the boiler!

We specifically designed System 2000, 90+ Resolute, and Accel CS to virtually eliminate the energy losses found in all other boilers, losses that are NOT measured by AFUE. To make the highest efficiency boilers, we combine the best technology: our unique well insulated low mass boilers, our high performance hot water system, and our Hybrid Energy Recovery (thermal purge) control. This delivers unsurpassed comfort and the lowest fuel bills.

In fact, oilheat System 2000 had a higher annual efficiency than all other boilers tested, including 95 AFUE and all other condensing boilers! And now, 90+ Resolute and Accel CS achieve even higher annual efficiencies, squeezing more out of your energy dollars.

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The U.S. Department of Energy’s Brookhaven National Laboratory confirms: Energy Guide (AFUE) ratings miss significant areas of energy loss1

Savings with System 2000 are much greater than with comparably rated heat and hot water systems. System 2000 had the highest annual efficiency in the study – even better than the 95% AFUE boiler tested.

What many homeowners, business owners and heating professionals don’t know about AFUE increases heating bills and wastes energy. The bar graph below compares AFUE ratings to the real efficiency delivered for space heating and water heating over the course of a year. Be sure to take a look to get a better understanding of real efficiency to cut your fuel bills.

Real Fuel Efficiencies
Shown below are comparisons of fuel efficiencies among typical and top rated available home heat and hot water systems.


Lead ASHRAE Article Identifies AFUE Alone Fails to Indicate Performance and Deep Energy Savings Potential

The industry’s preeminent heating, air conditioning and refrigeration engineering society, ASHRAE, has published “Performance of Combination Hydronic Systems” by Thomas Butcher, PhD, as the December 2011 cover story in the ASHRAE Journal. This article highlights that the current practice of labeling heat and hot water appliances with AFUE alone fails to indicate the actual annual performance and to identify the deep energy saving potential possible with a system upgrade.

Energy Kinetics has always been focused on delivering the best efficiency, and System 2000’s performance stands out in the study with the highest annual efficiency and the lowest idle loss (0.15%).  System 2000 significantly outperforms the 95 AFUE modulating condensing boiler and al other systems tested from around the globe. Our unique purge control strategy, low mass design, and high performance water heating system results in the top rating, and virtually eliminates the effects of oversizing.  The next best system in the study had an idle loss of four times System 2000, which resulted in higher annual fuel use and significantly lower efficiency during hot water production.


This chart summarizes findings in U.S. Department of Energy’s Brookhaven National Labs studies.1The large yellow numbers indicate efficiencies.

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Nearly 40% average savings were achieved by installing System 2000 to replace cast iron boilers rated at 85%-86% AFUE.

In this multi-year study, the U.S. Coast Guard in Kodiak, Alaska, replaced (24) new 85% and 86% AFUE cast iron boilers of various makes, indirect water heaters, and electric water heaters with System 2000 in residences.

The tremendous savings led to the 2007 replacement of another (149) cast iron boilers as part of a Super Energy Saving Performance Contract (Super ESPC) which is run by the Federal Energy Management Program (FEMP). This project capitalizes on the expertise and financing of the ESPC contractor to assist the Coast Guard in complying with the recent Executive Order which requires all Government agencies to reduce their energy use by 20% by 2015. The Coast Guard also realized operations and maintenance savings with System 2000 over the cast iron models. The FEMP takes advantage of real efficiency over AFUE, and you can too!

[ Read Looking Ahead in First Regional Super ESPC: Success on Kodiak Island, Alaska]

afue-BrookhavenBrookhaven National Laboratory study uncovers a need to retool boiler energy efficiency rating programs.
[ View Summary] or [ View Report ] What are Department of Energy National Laboratories?
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Brookhaven National Laboratory study uncovers a need to retool boiler energy efficiency programs

AFUE (government efficiency) ratings can be off by 25% or more, an error that can underestimate fuel consumption by up to 47%.

The study shows that a consumer who purchases a home heating system based only on a comparison of AFUE ratings may actually spend as much as $800 per year more on fuel with one system, compared to a second system with a nearly identical AFUE rating. This difference in real annual efficiency is determined by a characteristic of all heating systems called idle loss, a performance factor which is not evaluated for AFUE on units which provide both heat and hot water. Idle loss includes two primary areas of heat loss on conventional home heating systems: standby loss, and jacket loss. Also almost entirely neglected are draft regulator, draft hood, and room air losses.

In the study, the reduction of idle losses is identified as a primary factor in improving real system efficiency.

Only when idle losses are reduced or eliminated is it possible for real efficiency to approach the AFUE rating of a heating product. In fact, significant idle losses may lead to actual efficiencies as low as 55%. This real annual efficiency rating may determine system performance even when the government AFUE rating measures in the 80-95 percentile range.

The study also reports that the cold start and cold finish operation of Energy Kinetics’ System 2000 has the lowest overall idle loss and the best annual efficiency performance among all home heating systems tested to date, including 95% AFUE condensing gas and oil systems.

The study revealed that outdoor reset controls may save 5% to 15%, but need trial and error adjustments over the course of a heating season. By comparison, using proven Hybrid Energy Recovery,® System 2000 automatically adapts to heating loads. The result is a home heating system that delivers the best documented efficiency. View our efficiency checklist to see how your heating system idle loss compares.

[ View Checklist ]


Article: AFUE ratings do more harm than good…

AFUE ratings don’t help consumers make educated decisions about a boiler heating system’s efficiency.

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How do low-efficiency boiler controls artificially boost AFUE ratings and undermine efficiency?
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How much of your home’s energy is used for heat and hot water?

Find out more about conservation and about the impact of saving energy and about renewable energy.
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The chart at left is created from source data from the Energy Information Administration, Office of Energy Markets and End Use, Forms EIA-457 A-G of the 2001 Residential Energy Consumption Survey, New England and Mid-Atlantic states. Air conditioning percentage is an aggregate for the region and may not be representative of specific home usage.

1Data and conclusions are drawn from the report “Performance of Integrated Hydronic Heating Systems” (2007), Energy Resources Division, Department of Energy Sciences and Technology, Brookhaven National Laboratory, Under Contract No. DE-ACO2-98CH10886 with the United States Department of Energy by Dr. T. Butcher; and “Chimney Related Energy Losses in Residential Oil-Fired Heating Systems” (1990), with the addition of Accel CS and 90+ Resolute. Note: Higher operating temperatures reduce condensing boiler annual efficiency; the AFUE standard prescribes lower boiler temperatures than are commonly required for heating American homes during winter months.
[ View Paper ] [ View Presentation ]290+ Resolute Oil and Accel CS are certified as Most Efficient ENERGY STAR® products in 2016.