Watch Those Lights!

Today is “National Cut Your Energy Costs” Day, the day when we think about using less electricity in our homes, gasoline in our cars, and other forms of energy. Do you know what things in your house use the most energy?  Here at Bedtime Math we watched our electricity meter while running one appliance at a time, and found out that the clothes dryer uses about 1/5 of all our energy — and that we use more over the years because we have more kids now, which means more laundry, which means more loads in the machine every week. And as everybody gets bigger and dirtier, there’s more and more laundry. What will help someday is to save costs by finding energy that doesn’t cost much to begin with. One solar panel 2-3 feet long can make up to 300 watts and run a few light bulbs; better yet, a megawatt of energy from a wind farm can power 400 homes. If we can lasso the sun and wind even more cheaply, maybe someday we can dry our clothes as much as we want.

Wee ones: Try to find 3 light bulbs in your home that are on right now.

Little kids: If it’s sunny from 1:00 in the afternoon till sunset at 8:00 pm, how many hours can you leave the lights off?  Bonus: If 1 giant windmill, or “turbine,” on a wind farm can power 10 houses, how many houses can 10 turbines run? Count up by 10s!

Big kids: If a solar panel can run 4 light bulbs and your home has 32 bulbs in the various rooms, how many panels do you need to stick on your roof to run them all?  Bonus: If you see in the dark using night vision goggles instead of the 6 60-watt light bulbs in your kitchen, how many watts are you saving?




Wee ones: Count them as you find them: 1, 2, 3.

Little kids: 7 hours.  Bonus: 100 houses: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100.

Big kids: 8 panels.  Bonus: 360 watts.

Recent Posts

Pick a Math Skill

Pick a Topic

50 States


Daily Routine




Science and Nature


Vehicles and Transportation