Kilowatt Calculator

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• Conversion card (PDF)
• Formula card (PDF)
• Energy calculator (XLSX)
• Appliance log (PDF/DOCX/XLSX)

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Free printables

Single sheets you can print right now, no sign-up. The full pack adds every sheet in one download plus the editable files.

Printable Kilowatt Conversion Card1 page · free PDFPrintable Kilowatt Formula Card1 page · free PDFPrintable Home Energy Calculator2 pages · free PDFPrintable Appliance Energy Log1 page · free PDF

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kW vs kWh

Your electricity bill counts kWh (often called “units”). A device’s kW rating tells you how quickly it uses them.

Power conversions

Volts and amps to kilowatts

Power factor (PF) is 1 for purely resistive loads such as heaters and kettles, and lower (often 0.8–0.95) for motors and many electronic devices. If you don’t know it, the kVA figure gives an upper bound.

Worked examples

A 13 A appliance on a 230 V single-phase supply with a power factor of 1 uses 230 × 13 = 2,990 W, about 3 kW. A three-phase motor drawing 20 A at 400 V with a power factor of 0.85 uses √3 × 400 × 20 × 0.85 ≈ 11.8 kW. A 2 kW heater running 1.5 hours a day for 30 days uses 2 × 1.5 × 30 = 90 kWh; at 25 cents per kWh that is $22.50 a month.

Typical appliance power

Check the rating plate or manual for your appliance; plug-in energy monitors measure actual use.

Reading your electricity bill

Bills usually show the kWh used in the period (from meter readings or estimates), the price per kWh — sometimes different for peak and off-peak hours — and a fixed daily standing or service charge that you pay regardless of use. To check an appliance’s share, multiply its kWh by your unit price and compare with the energy part of the bill, not the total. Time-of-use tariffs make the timing of heavy loads such as laundry, dishwashers and car charging as important as the amount.

Heat pumps, heaters and efficiency

A resistive electric heater turns 1 kW of electricity into about 1 kW of heat. A heat pump moves heat rather than making it, so it can deliver roughly 2.5–4 kW of heat for each kW of electricity in suitable conditions — its coefficient of performance (COP). That is why heating costs depend so much on the type of heater, and why the kW on a heat pump’s label may describe heat output rather than electricity input; check which figure you are using.

Standby and always-on loads

Small loads add up because they run all day. A device drawing 5 W continuously uses 5 × 24 × 365 ÷ 1,000 ≈ 44 kWh a year; ten such devices use over 400 kWh. Routers, set-top boxes, smart speakers, chargers and appliances with clocks all contribute. A plug-in energy monitor shows the standby draw; switching off at the wall or using smart plugs on a schedule can trim the total.

Sizing circuits and generators

These are planning estimates; electrical installation and generator connection should follow local regulations and be done by qualified people.

Reducing energy costs

• Target the biggest users first: heating, cooling, hot water and cooking.
• Use timers and thermostats to cut running hours.
• Replace old incandescent bulbs with LEDs.
• Switch off devices on standby when practical.
• Check your tariff for cheaper off-peak hours for dishwashers, laundry and EV charging.

The energy pack

The optional pack includes a printable power conversion card, an appliance energy log, an Excel home energy calculator with monthly and annual costs, and a three-phase formula card. The calculator on this page is free.

AI-assisted content

This page was drafted with AI assistance and reviewed before publishing. Electrical installation work should be done by qualified people following local regulations.