# Boiler heat recovery: Correlation Prices it moves with, and why Source page: https://www.materialinsights.org/energy/e_boiler_recovery/correlation/ Economisers, condensing boilers and condensate systems are built from steel and stainless tube, priced with boilers. The proxy is the US power boiler and heat exchanger index. Their value rises with fuel prices, since every unit of heat recovered is fuel not bought. Proxy **US PPI: power boiler and heat exchanger manufacturing** index · monthly, Jan 2006 to Sep 2026 There is no free public price for boiler heat recovery itself, so this tab uses the closest public series as a stand-in. Read the numbers as an indication, not as the price of this exact item. #### What its price moves with Selected link ##### Boiler heat recovery and Steel Monthly changes 0.32 weak correlation 12-month changes 0.45 moderate correlation Last 5 years 0.05 monthly changes Lead or lag none No clear lead or lag Price function, Jan 2006 to Sep 2026 Boiler heat recovery ≈ 3.18 × (Steel)^0.75 R² 0.64 On this fit, a 10% higher steel price goes with a 7.4% higher boiler heat recovery price over the long run. Units: index and index, BLS base period. Chart: Boiler heat recovery and Steel prices rebased to 100 at Jan 2006, log scale Both prices rebased to 100 at Jan 2006, on a log scale so equal percentage moves look the same size. Chart: Boiler heat recovery price against Steel price, monthly, log scales, with fitted line Each dot is one month; paler dots are older (2006), darker dots recent (2026); the ringed dot is the latest month. The dashed line is the fitted price function. Both axes are logarithmic. Commodity [St Steel](https://www.materialinsights.org/commodities/steel/)Main material 0.32 Economisers and boiler tubes are carbon and stainless steel. Monthly moves correlate at 0.32 and yearly at 0.45, a weak to moderate link, because fabrication labour and engineering add much to the metal cost. weak co-movement month to month · 249 months Show charts Energy [HX Heat exchangers and pinch integration](https://www.materialinsights.org/energy/e_heat_exchangers/)Same fabricators 0.79 Boiler heat recovery uses the same tube and plate exchangers as other industry, made by the same firms. Monthly moves correlate at 0.79 and yearly at 0.90, a strong common driver of fabrication costs. strong co-movement month to month · 249 months Show charts Energy [Gas Natural gas](https://www.materialinsights.org/energy/natural_gas/)Fuel saved 0.02 Condensing boilers and economisers cut gas use, so dear gas raises their payback. Yearly moves correlate at 0.50 with European gas, a moderate link from shared industrial and energy cycles. little or none co-movement month to month · 249 months Show charts Energy [Tc Thermal coal](https://www.materialinsights.org/energy/thermal_coal/)Fuel saved 0.11 Coal-fired boilers in power plants and industry fit economisers and air heaters to save fuel. Monthly moves correlate at only 0.11 with coal, because equipment prices follow manufacturing costs, not fuel markets. little or none co-movement month to month · 249 months Show charts Energy [ST Steam turbines and thermal power plants](https://www.materialinsights.org/energy/e_steam_turbines/)Steam system 0.26 Boilers raise steam for turbines, so boiler and turbine orders rise together with thermal power building. Monthly moves correlate at 0.26, a modest link from shared projects and heavy fabrication. weak co-movement month to month · 234 months Show charts Chemical [WT Water treatment chemicals](https://www.materialinsights.org/chemicals/water_treatment/)Condensate quality 0.17 Recovering condensate saves water and treatment chemicals, which keep boilers free of scale and corrosion. Yearly moves correlate at 0.58 with the water treatment index, mostly a shared US industrial price trend. little or none co-movement month to month · 249 months Show charts How to read these numbers **Correlation of monthly changes** (the number in the coloured pill) compares how much each price moved, month by month, since 2006 or the first month both series exist. It runs from −1 to +1: near +1 the two usually rise and fall in the same months, near 0 there is no link, and a negative number means they tend to move in opposite directions. Above 0.7 is strong, 0.4 to 0.7 moderate, 0.2 to 0.4 weak. **12-month changes** compare year-on-year moves, which shows whether two prices share the same cycles even when the month-to-month noise differs. **Price function** is a straight-line fit of the two prices on logarithmic scales: price ≈ k × (partner price)^β. β is how much this price moves, in per cent, for a 1% move in the partner over the whole period, and R² is the share of the variation the fit explains. Two prices that both drift up with inflation can fit well without any real link, so read it together with the monthly correlation. **Lead or lag** checks whether the monthly correlation is clearly higher when one price is shifted by 1 to 6 months. Correlation is not cause. The reasons on each card explain the economic link; the numbers show how strongly it has shown up in prices. Proxy series are US producer price indexes or related prices and can blur the real link. Data: World Bank Commodity Price Data (Pink Sheet), October 2026; US Bureau of Labor Statistics producer price indexes, IMF primary commodity prices and US EIA prices via FRED, Federal Reserve Bank of St. Louis, retrieved November 2026. Calculations by this site. ## Other sections - [Summary](https://www.materialinsights.org/energy/e_boiler_recovery/index.md) - [Overview](https://www.materialinsights.org/energy/e_boiler_recovery/overview/index.md) - [Science and thermodynamics](https://www.materialinsights.org/energy/e_boiler_recovery/rc-sci/index.md) - [Engineering and integration](https://www.materialinsights.org/energy/e_boiler_recovery/rc-eng/index.md) - [Economics and contracts](https://www.materialinsights.org/energy/e_boiler_recovery/rc-econ/index.md) - [Impact and additionality](https://www.materialinsights.org/energy/e_boiler_recovery/rc-impact/index.md) - [What to track](https://www.materialinsights.org/energy/e_boiler_recovery/tracking/index.md) - [Relationships](https://www.materialinsights.org/energy/e_boiler_recovery/links/index.md)