An alarm clock or cellphone charger might consume 10 watts on average plugged into the outlet. If that 10 watt device is left in the outlet 24 hours a day for 365 days a year, it will consume approximately 87.5 kWh year.

For the sake of this analysis, let’s assume that we use 100% coal fired electricity, sold a residential home for 15 cents per kWh:

• $0.15 per kWh (Hudson Valley price)
• 1.04 lb of coal consumed per kWh (modern coal plant with NOx and SOx controls)
• 0.35 lb of coal ash produced per kWh (modern coal plant with NOx and SOx controls)
• 0.7 gallons of water consumed per kWh (modern recirculating water coal plant, water discarded as vapor in cooling tower)

In one year that 10 watt device will use:

• $13.13 in electricity
• 91 lb of coal burned
• 30.6 lb of coal ash landfilled
• 61.25 gallons of water