Calculator Inputs
Enter appliance details, runtime, tariff, and optional standby settings.
Formula Used
This calculator converts power and runtime into energy, then estimates cost, standby usage, and emissions.
Total Connected Load = Watts × Quantity
Effective Active Load = Total Connected Load × Duty Cycle ÷ 100
Active Hours Total = (Hours per Day + Minutes ÷ 60) × Days
Active kWh = Effective Active Load × Active Hours Total ÷ 1000
Standby kWh = Standby Watts × Quantity × Standby Hours Total ÷ 1000
Total kWh = Active kWh + Standby kWh
Estimated Cost = Total kWh × Electricity Rate
Estimated Emissions = Total kWh × Emission Factor
How to Use This Calculator
- Enter the appliance name, rated watts, and number of units.
- Add daily active runtime using hours and extra minutes.
- Set the number of days for the estimate.
- Use duty cycle for appliances that cycle on and off.
- Add standby watts if the device draws idle power.
- Enter your local electricity price per kWh.
- Optionally add an emission factor for carbon estimates.
- Press Calculate Energy Use to show results, graph, and export options.
Example Data Table
These examples assume rated power during active operation, 100% duty cycle, and no standby load.
| Appliance | Watts | Qty | Hours/Day | Days | kWh | Cost @ Rate |
|---|---|---|---|---|---|---|
| Ceiling Fan | 75 | 2 | 8h 30m | 30 | 38.25 | 5.74 |
| Laptop | 65 | 1 | 6h | 22 | 8.58 | 1.29 |
| Space Heater | 1500 | 1 | 4h | 15 | 90.00 | 13.50 |
| LED Bulb Set | 9 | 8 | 5h | 30 | 10.80 | 1.62 |
| Water Pump | 750 | 1 | 1h 30m | 20 | 22.50 | 3.38 |
Frequently Asked Questions
What is the difference between watts and kWh?
Watts measure power at one moment. kWh measures energy consumed over time. A 1000-watt device running for one hour uses 1 kWh.
Why does quantity matter in this calculator?
If several identical devices run together, their power adds up. Two 100-watt devices draw 200 watts, so energy use doubles for the same runtime.
What does duty cycle mean?
Duty cycle shows how much of the active period a device actually runs at rated power. Compressors, pumps, and thermostatic loads often average below 100%.
Why include standby watts?
Many devices still consume power while idle. Standby wattage captures hidden usage from routers, televisions, chargers, and smart appliances for better estimates.
Can I use my local electricity tariff?
Yes. Enter the price per kWh in your own currency. The cost result uses the same unit, whether it is rupees, dollars, euros, or cents.
Why might the estimate differ from my bill?
Bills may include taxes, tiered rates, minimum fees, demand charges, or inaccurate nameplate power. Measured wattage usually produces more realistic results.
What does the Plotly graph show?
The chart displays cumulative active energy, standby energy, and cost across the selected days. It reveals how usage and spending grow over time.
Can this help with solar or battery planning?
Yes. It is useful for load planning and daily energy budgeting. For full system design, also consider surge loads, efficiency losses, and backup days.