# Using Electricity

Part of the Engineering Merit Badge Digital Resource Guide: [Introduction & Overview](https://merit-badge.university/merit-badges/engineering/guide/index.md)

*6. Hands-On Engineering*

> **6b.** Make a list of 10 electrical appliances in your home. Find out approximately how much electricity each uses in one month. Learn how to find out the amount and cost of electricity used in your home during periods of light and heavy use. List five ways to conserve electricity.

Your home's electricity bill is a mystery to most people — a number shows up, you pay it, and that is the end of the thought. But behind that number is a fascinating system of generation, transmission, and consumption that electrical engineers designed. Understanding how much electricity your appliances use gives you the power to make smarter decisions about energy.

## Step 1: List 10 Electrical Appliances

Walk through your home and identify 10 appliances that use electricity. Pick a variety — some that run constantly and some you use occasionally. Here is how to organize your list:

| Appliance | Location | Estimated Watts | Hours Used/Day | Monthly kWh |
|---|---|---|---|---|
| Refrigerator | Kitchen | 150 | 24 (runs ~8 hrs actively) | ~36 |
| Central AC | Whole house | 3,500 | 8 (summer average) | ~840 |
| Clothes dryer | Laundry room | 5,000 | 1 | ~150 |
| Television (55") | Living room | 100 | 5 | ~15 |
| Laptop computer | Bedroom | 50 | 6 | ~9 |
| Microwave oven | Kitchen | 1,200 | 0.25 | ~9 |
| LED light bulbs (10) | Throughout | 10 each = 100 | 6 | ~18 |
| Dishwasher | Kitchen | 1,800 | 1 | ~54 |
| Washing machine | Laundry room | 500 | 0.75 | ~11 |
| Gaming console | Bedroom | 200 | 3 | ~18 |

*Note: These are approximate values. Your actual numbers will vary based on your appliances.*

## Step 2: Calculate Monthly Electricity Use

Electricity is measured in **kilowatt-hours (kWh)**. One kilowatt-hour means using 1,000 watts for one hour. Here is the formula:

**Monthly kWh = (Watts x Hours per Day x 30 days) / 1,000**

For example, a 100-watt TV watched 5 hours per day:
(100 x 5 x 30) / 1,000 = **15 kWh per month**

### Where to Find Wattage

- **The appliance label** — Look for a sticker or plate on the back or bottom listing watts, amps, or both
- **The manual** — Check the specifications section
- **Online** — Search for your appliance model number plus "wattage" or "power consumption"
- **A kill-a-watt meter** — This inexpensive device plugs into the wall and measures exactly how much electricity an appliance uses (about $20–$30)

> **Tip**
>
> If the label shows amps instead of watts, multiply by your home's voltage (120 volts in the US) to get watts. A hair dryer rated at 12.5 amps uses 12.5 x 120 = 1,500 watts.

## Step 3: Understanding Your Electric Bill

Your electricity bill tells an engineering story. Here is what to look for:

### Reading the Meter

Your electric meter measures total kWh consumed. Modern digital meters display the reading directly. Older analog meters have spinning dials you read right to left. Your utility company reads the meter each billing period and charges you for the difference.

### Light Use vs. Heavy Use

Electricity use varies by season and habit:

- **Heavy use periods**: Summer (air conditioning), winter (electric heating), evenings (cooking, TV, lighting all at once)
- **Light use periods**: Spring and fall (no heating or cooling), midday when the house is empty, overnight

Some utility companies charge different rates depending on the time of day — this is called **time-of-use pricing**. Electricity costs more during **peak hours** (typically 2–7 PM on weekdays when demand is highest) and less during **off-peak hours** (nights and weekends).

> **Did You Know?**
>
> The average American home uses about 886 kWh of electricity per month — roughly the same amount of energy contained in 75 pounds of coal. In some states, the average is much higher (Louisiana averages over 1,100 kWh) and in others much lower (Hawaii averages about 500 kWh).

## Step 4: Five Ways to Conserve Electricity

Here are proven strategies — pick five that apply to your home and explain why each one works:

1. **Switch to LED bulbs** — LEDs use 75% less electricity than incandescent bulbs and last 25 times longer. Replacing 10 incandescent 60-watt bulbs with 10-watt LEDs saves about 45 kWh per month.

2. **Unplug "vampire" devices** — Many electronics draw power even when turned off (TVs, game consoles, chargers). This phantom load can account for 5–10% of your electricity bill. Use a power strip and switch it off when devices are not in use.

3. **Use a programmable thermostat** — Heating and cooling typically account for about half of a home's electricity use. Setting the thermostat back 7–10 degrees for 8 hours a day can save up to 10% annually.

4. **Wash clothes in cold water** — About 90% of the energy a washing machine uses goes to heating the water. Modern detergents work just as well in cold water.

5. **Air-dry dishes and clothes** — Skip the dryer's heated drying cycle in the dishwasher. Hang clothes on a line or drying rack instead of using the clothes dryer, which is one of the most energy-hungry appliances in any home.

6. **Upgrade old appliances** — ENERGY STAR certified appliances use 10–50% less energy than standard models. A new ENERGY STAR refrigerator uses about half the electricity of one made 15 years ago.

7. **Use natural light** — Open curtains and blinds during the day instead of turning on lights. Position desks and reading areas near windows.

> **Safety First!**
>
> Never open electrical panels, modify wiring, or work with live electrical circuits. Reading your electric meter from the outside is safe, but leave any work inside the breaker box to a licensed electrician. If you use a kill-a-watt meter, only plug it into standard outlets — never attempt to measure hardwired appliances like your oven or central air conditioner.

![A teenager in a Scout uniform in a kitchen, crouching to read the label on the back of a microwave oven, with a notebook in hand documenting wattage information for an electricity audit](https://ik.imagekit.io/doulacoop/tr:w-800/mbu-assets/merit-badges/engineering/guide/home-electricity-audit?v=6f1ca6d1)

[U.S. Energy Information Administration — Electricity Explained](https://www.eia.gov/energyexplained/electricity/): Comprehensive guide to how electricity is generated, delivered, and used in the United States — with data on residential consumption by state.

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