The Carnot limit is two centuries old. The Karnot lever is the only way out.

What the Carnot limit actually is

In 1824, a young French engineer named Sadi Carnot published a slim book called Reflections on the Motive Power of Fire. In it he proved a result that has never been overturned: no heat engine can convert all the heat in a fuel into useful work. The maximum theoretical efficiency depends entirely on the temperature difference between the heat source (the combustion chamber) and the heat sink (the cooling tower, the exhaust, the atmosphere).

The formula is:

η_max = 1 − (T_cold / T_hot)   (temperatures in kelvin)

For a typical diesel engine, T_hot in the combustion chamber is around 2,000 K and T_cold at the exhaust is around 700 K. That gives a theoretical maximum efficiency of about 65%. Real-world losses (friction, incomplete combustion, exhaust enthalpy) drop the delivered figure to around 40%. The other 60% of the diesel you bought goes up the exhaust pipe as heat.

The efficiency ceiling, by technology

Every fuel-burning technology in commercial use sits below the Carnot ceiling — and the ceiling has not moved in two hundred years:

Why the heat pump isn't on the same chart

The figure above is a trick — heat pumps don't belong on a "combustion efficiency" axis, because they don't combust anything. The comparison is misleading on its own terms. But it is useful because it shows the only honest answer to the question every facility manager asks: "How can my heat pump be 450% efficient?"

The answer is that the percentage is the ratio of useful heat delivered to electricity consumed. A heat pump with a COP of 4.5 delivers 4.5 kilowatt-hours of useful heat to your hot water tank for every 1 kilowatt-hour of electricity it consumes. The other 3.5 kilowatt-hours came from the ambient air outside the unit — they were already there, free, owned by no-one. The compressor just moves them.

The Carnot limit doesn't apply because we are not converting heat to work; we are using a small amount of work (the compressor) to move a larger amount of heat from a low-temperature reservoir (the air) to a high-temperature reservoir (the hot water tank). That is the entire trick. And it has been industrially available for over a hundred years — your refrigerator at home does the same thing in reverse.

What this means at your facility

Take a 100 kW thermal load — typical for a mid-size hotel laundry, food manufacturer or hospital DHW. Run it through the four common heat-delivery technologies, at Meralco GP April 2026 tariff (~₱14/kWh) for the electrical case and post-Hormuz diesel at ₱90/L for the combustion case:

The Karnot iHEAT row is not a marketing number — it's arithmetic. One kilowatt-hour at ₱14 × 22 kWh of electrical input per 100 kWh of useful heat delivered = ₱308/day on input electricity. Add demand-charge and a maintenance allocation and the all-in cost lands around ₱4,300/day. The diesel and LPG rows assume current Philippine prices — and assume the fuel actually arrives, which after 70+ days of Strait of Hormuz closure is not a safe assumption.

"Why hasn't anyone else done this in the Philippines?"

This is the most common follow-up question, so worth addressing directly. R290 heat pumps have existed in Europe for over thirty years. CO₂ refrigeration has thirty years of industrial history. Solar plus storage is now off-the-shelf. None of this is invention.

What is new — and what Karnot is the only company in the Philippines doing — is integrating all four (heat pump, thermal storage, solar, measurement) under one contract, with M&V on both ends of the install. Most installers in the Philippines sell one box. The solar people sell solar. The HVAC contractors sell heat pumps. None of them measure the baseline. None of them prove the saving. Once you've sold the box, the integration becomes the customer's problem.

Karnot is small enough — and stubborn enough — to design the whole system instead of selling its components. Eventually someone bigger will do this in Manila; probably one of the European OEMs setting up here in the next three to five years. Until then we are alone in the market we made.