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Getting to know kWh as the first step to lowering electricity costs

Ever wondered what can be done to lower the electricity bill? A concept central to electricity usage is kilowatt-hour (kWh), and understanding what it is can help you monitor usage and make smart choices for lowering your costs.  


The electricity bill states how many units of electricity a user has consumed. This unit is kWh, which equals the amount of energy needed for running a 1,000-watt electrical appliance consecutively for an hour.


According to the Electrical and Mechanical Services Department, the average amount of electricity consumed per person in residential households was 1,733 kWh in 2020. For each kWh, Hong Kong's two electricity companies charge users an average net tariff of HK$1.42 or HK$1.66. 


What can 1 kWh power?

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To calculate the kWh of a specific appliance, you can multiply its power rating (watts) by the number of hours you use it, then divide the amount by 1,000. Here are examples of how long 1 kWh can power an item: 


- Air-conditioner (1 HP): 1 hour 3 minutes 

- Standing fan: 13 hours 20 minutes

- Incandescent light bulb (100 watts): 10 hours 

- LED light bulb (7 watts): 142 hours 51 minutes 

- Laptop computer: 7 hours 24 minutes 

- Mobile phone: 100 hours 


Implications of kWh 


1. Cost 


Knowing the kWh of appliances can help estimate electricity costs. You can also change your consumption habit to save costs – the kWh of a fan is a fraction of an air-conditioner, and that of an LED light is significantly lower than an incandescent light bulb. 


2. Environmental impact

Electricity generation, a big part of which comes from fossil fuels, remains a major source of carbon  emissions. For every 1 kWh of electricity generated, around 0.39 carbon dioxide equivalent (CO2e) is emitted.

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A mature tree absorbs 25 kg of CO2 per year, meaning it would take it 55 years to absorb the carbon emissions of a resident's annual electricity consumption. 

With every kWh saved, you can put extra cash in your piggy bank and contribute to preserving our planet. Let's start by checking the kWh of common household appliances here and rethink your usage pattern!

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