When you're shopping for a new HVAC system for your $350,000 home, the specs can feel overwhelming. One contractor quotes in BTUs, another in tons, and the energy guide shows kilowatts. That's where a power converter becomes essential. Whether you're comparing a 3,500-watt generator for camping, calculating how much a 1,500-watt space heater will add to your electric bill, or figuring out if a 2-horsepower sump pump is enough for your basement, understanding power conversions saves money. Americans waste hundreds of dollars annually by misjudging power requirements. This calculator instantly converts between watts, kilowatts, horsepower, BTUs per hour, and more—helping you make informed decisions on appliances, tools, and home improvements.
How to Use
Select your input unit (watts, horsepower, BTU/hr, etc.), enter the value, then choose your desired output unit. The calculator instantly displays the converted result. Use it to compare appliance specs, size generators, or understand energy labels on everything from air conditioners to power tools.
Pro Tips
When sizing a portable generator, list all devices you'll run simultaneously, then add 20% headroom for startup surges. For solar panel planning, convert your daily kilowatt-hour usage to watts by dividing by peak sun hours (typically 4-6 in most US locations). Comparing central air conditioners? A 3-ton unit equals 36,000 BTU/hr or about 10.5 kW—knowing this helps you verify contractor quotes. Always check the yellow EnergyGuide label; it shows estimated annual operating costs in dollars based on national average electricity rates, making cross-brand comparisons straightforward.
Common Mistakes to Avoid
Confusing watts and watt-hours is the most frequent error. Watts measure power rate; watt-hours measure total energy consumed. A 100-watt bulb uses 100 watts regardless of how long it runs. Another mistake: assuming higher horsepower always means better performance. A 5-HP air compressor might actually deliver less usable air than a 3-HP model with better tank design. Finally, many Americans underestimate starting wattage for motors. A refrigerator rated at 700 running watts may need 2,200 watts to start—critical when sizing a backup generator for your home.
Frequently Asked Questions
How many watts can I safely run on a standard 15-amp household circuit?
A 15-amp circuit at 120 volts handles 1,800 watts maximum. For safety, stay under 1,440 watts (80% load). If you're running a 1,500-watt space heater, that circuit is essentially maxed out—plugging in anything else risks tripping the breaker.
Why do some appliances list horsepower while others show watts?
Traditional mechanical devices like motors and compressors often use horsepower, while electrical appliances use watts. One horsepower equals approximately 746 watts. A 2-HP shop vac draws roughly 1,492 watts—useful knowledge when deciding if your garage circuit can handle it.
How do I estimate the monthly cost to run a device?
Multiply watts by hours used daily, divide by 1,000 to get kilowatt-hours, then multiply by your electric rate. At the US average of $0.15/kWh, a 100-watt light running 8 hours daily costs about $3.60 monthly.