Build a multi-appliance total

Add appliances you care about, then see the combined kWh and cost. This is great for “why is my bill so high?” moments — and also for sharing with roommates/family when deciding what to cut back.

Quick “does this make sense?” guide

• 1,000 W for 1 hour ≈ 1 kWh.
• 1,500 W space heater for 3 hours/day ≈ 4.5 kWh/day → ~135 kWh/month.
• 10 W device 24/7 ≈ 7.2 kWh/month (standby power is real).
• Use duty cycle for devices that cycle on/off (fridges, AC, pumps).

How the Appliance Power Usage Calculator works

Most people think electricity bills are “mysterious,” but the math is actually simple: electricity is billed in kilowatt-hours (kWh), which is a measure of energy. Your appliances are rated in watts (W), which is a measure of power. Power tells you how fast the appliance uses energy. Time tells you how long it runs. Put them together and you get kWh — then multiply by your utility rate to estimate cost.

Utilities bill in kilowatts (kW) and kilowatt-hours (kWh). Since 1 kW = 1,000 W, we convert:

• kW = watts ÷ 1000

Energy is power multiplied by time:

• kWh (active) = (watts ÷ 1000) × hours/day × duty cycle × quantity × days

If your appliance runs continuously at the stated wattage (like a light bulb), duty cycle is 100%. But many big-ticket devices cycle on and off — refrigerators, air conditioners, dehumidifiers, well pumps, and some space heaters. In those cases, duty cycle helps you estimate the average power rather than the peak rating.

Many devices draw power even when “off” (standby): TVs, game consoles, chargers, printers, sound bars, smart speakers, and set-top boxes. Standby energy uses the same formula:

• kWh (standby) = (standby watts ÷ 1000) × standby hours/day × quantity × days

This calculator adds active kWh and standby kWh to get a total. If you don’t enter standby values, it assumes zero. If you enter standby hours, a good starting guess is 24 − active hours.

Utilities bill by energy consumed. If your rate is $0.16 per kWh, then:

• Cost = kWh × rate ($/kWh)

If you enter a CO₂ factor (kg CO₂ per kWh), the calculator estimates emissions:

• CO₂ (kg) = kWh × (kg CO₂ per kWh)

Because grid emissions vary by country/region and time of day, this is best used as a “ballpark” estimate.

• Example 1 — Space heater: 1,500 W for 3 hours/day, 30 days, $0.16/kWh, duty 100%.
  kWh = (1500/1000)×3×1×1×30 = 135 kWh/month → Cost = 135×0.16 = $21.60/month.
• Example 2 — TV + standby: 120 W for 4 hours/day, standby 2 W for 20 hours/day, 30 days, $0.16/kWh.
  Active kWh = (120/1000)×4×30 = 14.4 kWh. Standby kWh = (2/1000)×20×30 = 1.2 kWh.
  Total = 15.6 kWh → Cost = 15.6×0.16 = $2.50/month.
• Example 3 — Refrigerator (duty cycle): 150 W average while running, 24 hours/day, duty 35%, 30 days, $0.16/kWh.
  kWh = (150/1000)×24×0.35×30 = 37.8 kWh → Cost ≈ $6.05/month.

• Look for a label: Many appliances list watts (W) or amps (A). If you only have amps, you can estimate watts ≈ volts × amps (often 120V in the US).
• Use a plug-in meter: A Kill A Watt-style meter can capture real average watts and kWh over time.
• Use duty cycle for cycling devices: If the compressor runs ~8 hours/day on average, duty is 8/24 ≈ 33%.
• Be honest about usage: A 10-minute kettle use is 0.17 hours/day, not “1 hour.”

A good calculator doesn’t just do arithmetic — it helps you make decisions. With kWh and cost broken down, you can answer high-value questions like:

• “Is my space heater costing more than I think?”
• “How much would it save to switch from incandescent to LED?”
• “What’s my baseline standby ‘always-on’ cost?”
• “If I run my dryer 15 times a month, what’s the real impact?”
• “Which 3 appliances dominate my monthly usage?”

Use the Appliance List to build a mini audit. Add your heater, dryer, dishwasher, fridge, gaming console, and TV. The combined totals usually reveal a clear pattern — and once you see the pattern, the “what should we do?” decision becomes obvious.

Frequently Asked Questions

• What’s the difference between watts and kWh?

  Watts measure power (how fast energy is used). kWh measure energy (how much you used over time). Bills are based on energy (kWh).

• If my appliance says “1500W,” is it always using 1500W?

  Not necessarily. Many appliances vary by setting and cycle (heaters, fridges, AC). The label may show maximum draw. If it cycles, use a duty cycle (like 50% or 35%) or measure with a plug-in meter.

• What duty cycle should I use for a refrigerator?

  A common rough range is 25%–45% depending on temperature, age, and how often the door opens. If you’re unsure, start with 35% and adjust.

• Why does standby power matter?

  One device might be small, but many devices together can become a noticeable baseline cost. TVs, consoles, routers, chargers, and smart devices can quietly add kWh every month.

• Does this match my exact electric bill?

  It’s an estimate. Bills include tiered rates, taxes, fees, demand charges (some regions), and real-world variations. This tool is best for understanding relative impact and identifying big levers.

• How do I reduce my cost the fastest?

  Start with the highest monthly-cost items: space heaters, electric dryers, older fridges, and heavy HVAC use. Reducing hours or improving efficiency there usually beats optimizing tiny loads.