Energy Trust Blog, Jan. 5, 2017.
https://blog.energytrust.org/boiler-tune-cuts-j-h-baxters-annual-energy-costs-estimated-21100

"A Kewanee steam boiler is the backbone of J.H. Baxter & Co.’s wood-treatment facility in Eugene [Oregon]. But over time, the boiler’s fire tubes built up a layer of soot that decreased efficiency. The solution was a simple boiler tune-up that boosted efficiency by 8.5 percent, saving more than 41,000 therms per year. Not only did the project cut the facility’s annual energy costs by an estimated $21,100—90 percent of the cost of the tune-up was paid for through Energy Trust of Oregon’s 90 by 90 industrial operations and maintenance offer."