Boiler Feedwater Pre-Heat Calculator

Every 6°C rise in feedwater temperature cuts fuel consumption by approximately 1%. Lifting cold make-up water from 28°C to 85°C — a 57°C rise — cuts boiler fuel by roughly 9-10% on the make-up flow alone, and shaves 20-35% off total fuel where condensate return is low.

iHEAT is Karnot’s industrial R290 (propane) heat pump platform — in full production today. R290 has a Global Warming Potential of just 3 (versus 2,088 for R410A) and delivers a COP of 3.0-3.5 producing hot water up to 75°C — perfect for boiler feedwater preheating into the deaerator. Single units run 9.5 to 50 kW, with parallel master/slave stacking up to 500 kW for larger boilers.

iSTOR is Karnot’s stratified thermal battery — an insulated tank that stores hot water at 85-95°C produced by the iHEAT during off-peak hours and discharges it on demand to the boiler. It allows a smaller heat pump to serve a peaky steam load and lets you charge the tank from solar PV during daylight hours (Power-to-Heat).

Yes. The fuel offset is calculated on the basis of thermal energy displaced, then converted back to litres of diesel, kg of LPG, m³ of natural gas, or litres of HFO using each fuel’s net calorific value and typical boiler efficiency. The calculator handles all four.

Payback is typically 2-4 years for diesel and HFO boilers in the Philippines, 3-5 years for LPG, and 4-7 years for natural gas (where available). The Karnot Energy-as-a-Service option removes CAPEX entirely — you simply pay a guaranteed-lower monthly fee.