Use live data to focus on lights

Use live data to explore how much power your school lighting is using

10 KS2 KS3 KS4 Citizenship Maths Science
 Let's focus on lighting to see how much power your classroom lights consume.

Switch off all the lights in your classroom.  Look at your live data and make a note of the live power consumption.

Now switch all the lights on.  How has the power consumption changed?  This is the amount of power that the lights were using right in the instant that they were on.

This power is measured in kW - kilowatts.

If a kettle, for example was turned on it might use 3 kW but if you turned it off again immediately, you will not have used much energy because that (power) consumption was only for a short period of time.   However if the same kettle was huge and took 30 minutes to boil, then it would have used 3 kW for 0.5 hour.

3 kW x 0.5 hour = 1.5 kWh

How much energy would be used to keep all the lights in your classroom on for one hour?
Can you calculate how much energy would be used if all the lights were switched on constantly from 9am to 3pm (6 hours)

If your school is large and you have efficient lights you might not see much difference to the total power use when you switch off one set of lights. Try turning off the lights in several classrooms, corridors or buildings to see if you can make a difference.  Keep track of what the power consumption was when all the lights were off and when they were all on.   


Do all the lights need to be on right now. Can you leave off some lights and save energy?


The average cost of electricity is 15p per kWh.  How much would it cost to keep your classroom lights on for one hour?  For a school day (6 hours)?  Can you calculate how much it would cost to light the area you examined above (several classrooms, corridors or buildings) for a school day? Week? School year (195 days)?

Make the change

How could you use this information to persuade school users to turn off lights when not in use?

An extra challenge for schools with fluorescent lights

A standard 150cm twin tube fluorescent light in a classroom will use around 140W. 
A standard 180cm twin tube fluorescent light will use around 170W. 
A 150cm LED twin tube will use around 50 W.  

Using what you've learned about how much electricity your school is using for lights, and how that adds up over time and with cost, can you calculate the long term savings you could make if you switched to LED lights throughout the school? 

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