Any homeowner looking to purchase a boiler will likely want to know how efficient their new system will be. The efficiency of boilers can vary significantly by type. Likewise, there are numerous kinds of boilers. Here is a closer look at which type of boiler is the most efficient.
Water Temperature
Hot Water Boilers
Hot water boilers are available in low and medium temperature ranges. Low-temperature models are typically employed for in-floor heating, producing temperatures between 85 and 140 degrees Fahrenheit. A medium-temperature model pushes between 140 and 175 degrees, which is ideal for radiant heating. Higher temperatures are available, but these tend to be for industrial and commercial applications. A hot water boiler usually operates in the 80% to 95% efficiency range, meaning that only 5% to 20% of the heat is wasted.
Steam Boilers
Rarely seen in residential settings, steam boilers heat the water above the boiling point and then pipe the resulting steam. These models have an efficiency rating between 75% and 85%.
Fuel Source
Gas
A gas boiler typically uses natural gas or propane as a fuel source. Traditional boilers of this type operate at about 80% efficiency. However, condenser models recapture much of the heat loss through ventilation. These models operate at efficiency levels between 90% and 98%. They also have some of the lowest emissions among systems that use fossil fuels.
Oil
Heating fuel is a particular type of oil that’s fairly uncommon here in Oklahoma, with less than 1% of systems employing it. Heating fuel systems require an on-site tank that can store at least 250 gallons. These models operate at about 80% to 90% efficiency.
Electric
Electric models run at 100% efficiency within the system. However, losses in electrical delivery reduce efficiency by as much as 20%. On-site electric generation, particularly solar panels, can make an electric boiler highly desirable.
Tube Design
Fire Tube
A fire-tube sends combustion gases into tubes. Water surrounds the tube, triggering the heat transfer process. They are desirable at locations that require consistent heating and a simple design. However, they also operate at about 75% to 85% efficiency in traditional designs.
Water Tubes
A water tube reverses the design. Water flows through the tubes, and then combustion gases surround it. This makes startups faster, and it works well in applications where demands frequently change. These models also typically operate at 80% to 90% efficiency in a traditional boiler.
Package Boilers
Many types of boilers require on-site assembly. A package boiler is a factory-assembled system on a skid. It moves into place as one piece and uses standard connections. Package boilers are usually about 5% less efficient than assembled models. However, the installation process is simpler. All major types of boilers by type and fuel source are available in package designs.
Residential Boiler Types
You can also think about your boiler in terms of how the overall system works. A conventional boiler uses separate hot and cold water tanks, and these designs work well in environments that have lots of space. They tend to be more cost-effective to install and run in the 80% to 90% efficiency range. Likewise, they use a simpler gravity-fed design that’s excellent for households with heavy demands.
System boilers heat and store hot water in a cylinder. They employ a pump and an expansion vessel but don’t need a cold water tank. This design can readily take water directly from the main water supply. The design tends to be more compact and will operate at about 85% to 90% efficiency with a condenser.
Combination boilers, often called combis, have a boiler and a hot water tank. In other words, they can provide for your heating and hot water consumption needs. They typically use an on-demand system without a tank, making them great for smaller homes. Combi models often operate at 90% to 95% efficiency, too.
Hybrid boilers are an interesting alternative. A hybrid boiler uses a boiler alongside a heat pump. The heat pump handles the work during cool conditions, and then the boiler activates when the weather gets cold. This allows the heat pump to work at efficiency levels well above 100% while providing enough heating capacity from the boiler to deal with deep freezes.
Considerations
How to Read Efficiency Ratings
The typical unit for efficiency is annual fuel utilization efficiency (AFUE). The AFUE rating tells you how much of every dollar you spend becomes heat inside your house. If a system has a 90% AFUE, then you expect 90 cents of every dollar to become usable heat while 10 cents end up as waste. Usually, most of the waste is lost through the ventilation of hot gases from the combustion process.
You may also see a thermal efficiency (TE) rating. The TE number tells you how much heat is lost during the heat exchanges from burning fuel, heating water, and then warming your home.
AFUE is almost always the better metric to look at. However, TE can help you compare systems with similar performance. Suppose two systems operate at 90% AFUE, but one runs at 90% TE and the other hits 95. Then, the system with the higher TE delivers a somewhat better transfer of warmth and, therefore, is better.
Comparing Boiler Types
If efficiency is your focus, then the biggest thing you’ll want to look for is a gas boiler that uses a condenser and water tubes. There is a case to be made for a hybrid boiler that includes a condenser, but be aware that these models often have high upfront costs and long payback periods. A combi boiler can be a good choice for added efficiency if you’d also like to eliminate your home’s water heater.
Electric boilers are less desirable because they’re only highly efficient with an on-site electricity source like solar panels. The electrical delivery process can be inefficient, and electric rates can be high in some areas.
We don’t recommend oil boilers because home heating oil is an uncommon fuel source in this part of the country. Likewise, oil boilers tend to be less efficient, although models with condensers can post competitive numbers. Similarly, we don’t recommend using a conventional gas boiler. While these models have lower upfront costs, they will cost you more money than you save within a few years of operation. We also strongly recommend replacing older models, which can have efficiency ratings below 60% in some cases.
Many households in Oklahoma City, OK and the surrounding metro area rely on True Climate Heat + Air for all their AC and heating services needs. Our licensed HVAC technicians have been proudly helping customers since 2005. You can check online ratings sites to see some impressive customer testimonials, too. We have 24-hour emergency availability, also.
Our company offers numerous specials. Anyone planning to install a boiler should talk with us about available financing options upon credit approval. We also install furnaces, heat pumps, and more.
If you’re considering installing or replacing a boiler at a home in or near Oklahoma City, contact True Climate Heat + Air today.
