Resources // Customer Stories

Considerations for Converting from Steam Heat to Hot Water


Steam heat has been around for a long time. Since the 1800’s steam has heated everything from single family homes up to large hospitals and factories. Simple to use with no need for pumps or any electricity at all. Biggest downfall: it is not very efficient, and it is difficult to control the heat.

Many buildings today were designed for steam heat, and still have low pressure steam heating. But with the continued demand for lower energy consumptions in all that occupies our daily lives, frequent review of steam heating systems often leads to recommending a conversion from steam to closed loop hot water heat.

In a steam boiler, heat transport occurs through the process of boiling water to produce steam. The heat from the combustion of fuel is transferred to the water in the boiler, causing it to reach its boiling point and turn into steam. The steam then carries the heat energy to various parts of the system, such as radiators or turbines, where it releases the heat and condenses back into water.

Diagram A – steam heating process

On the other hand, in a hot water boiler, heat transport takes place through the circulation of hot water. The heat from the fuel combustion is transferred directly to the water in the boiler, raising its temperature. The hot water is then pumped or circulated through pipes to different areas, such as radiators or underfloor heating systems, where it releases its heat energy and returns to the boiler to be reheated.

Diagram B – hot water heating process

Overall, both steam boilers and hot water boilers are used for heating purposes, but they differ in terms of the medium used for heat transport.

While it seems the conversion from steam to water heat is simple and can provide substantial energy savings, the complexity of converting an old building and old piping to hot water heat and the differences in the two processes can make the economics seem out of reach.

Energy Reduction

Considering cost savings can range from 10 – 25% in energy, as well as substantial utility rebates for a heating conversion, those economics are “closer than they appear”.

Consider a 50,000 square foot facility designed and built 40+ years ago. This building would likely have a boiler sized around 2500 MBH, yielding an annual fuel bill at today’s price of more than $45,000. Savings on this gas bill can go a long way to covering the cost of conversion and your utility rebate may pay for a sizable portion of the project. *

Cleaver Brooks hydronic high efficiency condensing units


When making the conversion from steam heat to closed loop hot water heat, two modifications are required. Modification or replacement of the boiler and addressing the distribution piping including radiation.

Boilers can be easily replaced with more efficient equipment, but at the same time existing steam boilers can be converted to hot water with relative ease, reducing some of the up-front cost. However, older boilers will have some limitations regarding minimum operating temperatures and efficiency. Newer boilers can provide lower operating temperatures and higher efficiency; however, the system (originally designed for steam) will be limited in how low water temperatures can be operated.

Before & after of a steam boiler to hot water boiler conversion by PBBS Equipment.
Savings result: $10,082/year (22% decrease in energy cost)

Old steam systems were designed to operate around steam temperatures of 220 – 240 degrees F. Modern hot water systems can operate around temperatures as low as 140 degrees F. To heat the same building with lower temperatures may require more radiators and bigger heating coils. If more radiation cannot be added, the hot water system temperatures will need to be higher to heat the space, defeating the effectiveness of high efficiency boilers.

In addition to temperature issues, pipe size in the old steam system will influence the cost of the conversion. While steam supply lines are generally sufficient for pumped water, the condensate return lines in the system are generally much smaller than would be needed for pumping water back to the boiler.

So, what is the trade off? Those answers come with a review of your current building and system. Contact PBBS Equipment today and we can provide dependable expertise during the initial review to provide solid financial direction for your heating needs.

*Figures based on Standard ASHRAE calculations for a facility in the upper Midwest.

boiler room gauge

Join Our Newsletter

Sign up to receive the latest news on boiler maintenance, service, and parts from PBBS.

Sign Up
Contact Us