Shopping for an air conditioner in the US means confronting BTU per hour — the 12,000 BTU window unit, the 24,000 BTU mini-split — while your electricity bill, your solar panels, and every physics formula on the planet speak watts. The two units both measure power (energy per unit of time), just in different dialects: the BTU is the energy needed to heat one pound of water by one degree Fahrenheit, and watts are joules per second. The exchange rate is 0.29307 — multiply BTU/hr by it to get watts. Type 12,000 into the BTU/hour (BTU/hr) box and the Watts (W) readout shows about 3,516.8, which is 3.52 kilowatts and roughly 4.72 horsepower in the other bonus boxes. That wattage is what actually spins your electric meter, so it is the number that predicts your summer power bill and tells you whether a generator or solar setup can handle the load. Furnaces, heat pumps, and even grills are rated in BTU/hr, so this one factor quietly governs most American heating and cooling decisions.

With the pre-filled defaults — BTU/hour (BTU/hr) 10,000 — the BTU/hr to Watt returns Watts (W) 2,930.70, Kilowatts (kW) 2.9307, Horsepower (hp) 3.9302. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.