Boilers, furnaces and stoves: Unit economics
Why a cheap boiler can burn millions in fuel
What this tab covers What it costs to move a unit of energy this way: capital and operating costs, tariffs, utilisation and how it compares with the alternatives.Fuel dominates the cost of combustion heat; the boilers themselves are cheap relative to the fuel they burn over their lives. That is why small efficiency gains pay back quickly, and why heat pumps, which cost far more to buy, can still compete.
Key costs
| Measure | Value | Note |
|---|---|---|
| Cost of industrial steam (DOE worked example) | 9.39 USD per 1,000 lb steam (illustrative gas price)3 | Natural gas at 8.00 USD/MMBtu, 450 psig saturated steam from 230 F feedwater, 85.7% combustion efficiency |
| Same steam at cheaper gas | about 4.1 (calculated) USD per 1,000 lb steam3 | Gas at an assumed 3.50 USD/MMBtu, same assumptions; cost scales with gas price |
| Boiler combustion efficiency by fuel | Gas 85.7%, distillate oil 88.7%, residual oil 89.6%, coal 90.3%%3 | Higher heating value basis, boilers with economiser or air preheater and 3% flue oxygen; gas is lower because more of its energy leaves as water vapour |
| Home boiler efficiency | 56 to 70% (old), 80 to 83% (mid), 90 to 98.5% (condensing)% AFUE4 | Upgrading a cold-climate gas-heated home from 56% to 90% avoids about 1.5 short tons (about 1.4 t) of CO2 a year |
| Industrial heat pump versus boiler capital cost | Heat pump about 10 times a gas boiler ratio12 | Shows how cheap boilers are to build |
| Time cost of traditional cooking | about 4 hours per day5 | Average for households without clean cooking access, spent collecting fuel and cooking on inefficient stoves |
Where the money goes
| Item | Share or amount |
|---|---|
| Fuel | The largest cost item; steam cost scales directly with fuel price divided by boiler efficiency3 |
| Capital | Small for boilers compared with fuel over the life12 |
| Losses | 36% of US process heating energy is lost (2010 data)2 |
Worked example (calculated): a factory uses 50,000 lb of steam an hour for 8,000 hours a year, 400 million lb. At 9.39 USD per 1,000 lb that is about 3.8 million USD a year in fuel. Raising boiler efficiency from 85.7% to 88% (for example with an economiser) cuts fuel use by about 2.6%, worth roughly 100,000 USD a year.
Sources
- Quadrennial Technology Review 2015, Chapter 6 Technology Assessment 6I: Process Heating US Department of Energy, 2015
- Benchmark the Fuel Cost of Steam Generation, Steam Tip Sheet #15 (DOE/GO-102012-3391) US Department of Energy, Advanced Manufacturing Office, 2012
- Furnaces and Boilers US Department of Energy, Energy Saver, 2025
- Clean Cooking in Africa 2026: Executive summary International Energy Agency, 2026
- Heat Pumps Step Up: What the IEA's Heat Pump Monitor 2026 Means for Heating, Industry and Energy Security IEA Heat Pumping Technologies TCP, 2026