How do you do the math for the cost of a light bulb or any electric appliance?

Question

To help the environment I want to know how and to keep my electric bill down. Electric water heaters, oven, and light bulbs. All I hear the environmentalist say is turn off the lights.

Answer 1

The practicalities of the maths involved with this do, in some cases, make it almost impossible. Light bulbs and water heaters without a thermostat use a constant power. A light bulb rated at say 100 Watts will use 100 Watts/hour  all the time it is switched on. Things like ovens, shower heaters and some electric kettles have thermostats. These items will use a rated power when switched on, but, at a preset temperature they will switch off until the temperature drops. Unless you put a power meter in circuit with these items and watched them continuously, you wouldn't know at what point they were using their rated power and when they were using nothing. Your heavy users are the things with heaters in them. Use these as sparingly as you can to keep your bills down

Answer 2

Most utility companies in North America send you a bill based on the number of Kilowatt hours your house hold consumes. A kilowatt is 1000 watts. If you consume 1000 watts of power for an hour, you will be billed 1 killowatt hour. Here is an explanation from Wikipedia:

"Consider a setup with two 50 W light bulbs (100 W total) left on for 10 hours per day. The setup will consume 1 kilowatt-hour per day. If a power company charges $0.10/kW·h, then those two light bulbs will cost $0.70 over the course of a week."

Just about all major appliances and electronic devices are required to have their power usage somewhere right on the appliance. By doing a little simple math, you can do an inventory of your power consumption in fairly short order.

Remember that devices that are energy star compliant use significantly less power when they are in sleep mode. Most of these devices also allow you to adjust their sleeping and waking intervals.

Answer 3

Very simple.

Watts of your actual light bulb                         60 Watts

Watts of the new efficient light bulb                23 Watts

Difference                                                         37 Watts

Hours that you light the bulb per yr            1,200 Hours

Energy Consumption                                 44,400 Watt hours

Divide that by 1000 to get KWH                       44.4 KWH

Cost per KWH                                                $0.10 /kWh

Saving per bulb                                              $4.44 / bulb

20 Bulbs in a house hold                               $ 88.80 per yr

To get the right amount you need to know how many hours you operate the bulb and the cost of your kWh. Yo can see the cost in your utility bill.

You can save water and electricity and avoid water pollution when you use a laundry ball to wash your clothes.

Look at www.laundryball.net

Good luck and save as much energy as you can.

We can help reduce global warming.

Answer 4

Take the number of watts times the time it is operating to get the watt-hours.  For comparing light bulbs you compare the lumens produced divided by the watts consumed.

Answer 5

Here's how to estimate costs/savings:

First, let's assume you replace items at the end of their "useful life."  Which i s asensible way of doing it--it means the money you spend to "go green" is limited to the difference between what you actually spend and what you would have had to spend anyway to replace an item, whether it's a light bulb or a car.

The math:  If the energy-efficient item costs more than a more conventional alternative (not all do--and if efficient alternatives are cheaper, it's a no-brainer) take the difference in cost between the two chooices--that's the added cost of the energy-efficient choice.

Next, figure out how much energy you will save (many products have guides to help you figure this out) and estimate how much that reduction in energy consumption will save you per month.  Finally, multiply that by the expected lifetime of the device--that gives you the total cost savings you can expect.  Subtract that from any added cost of purchasing the device.  Usuallly this will give you a negative number--you save more in the long run than you pay out to start with.  If it is a positive number, that's the long term cost to you of energy-efficiency in a particular case.

Although, quite honestly, there are very few situations in which you will not save money in the long run.  Even adding solar panels, while expensive, are  long-term money savers with today's technology.