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 CO₂ (R744) heat pump platform. CO₂ refrigerant has a Global Warming Potential of just 1, and its transcritical thermodynamic cycle is uniquely suited to producing 85-95°C hot water at high COP (3.0-4.5) — exactly the temperature window needed for boiler feedwater preheating.

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.