Energy Cost Calculator

An energy cost calculator estimates what it costs to run a household appliance from its wattage and daily usage, converting wattage into kilowatt-hours and multiplying by an electricity rate to produce daily, monthly, and yearly cost estimates for each device and a combined total.

• Each appliance entry has a name, a wattage rating, and the hours it runs each day. Wattage is usually printed on the device's label or listed in its manual; the field accepts fractions (such as 1/2), mixed numbers (such as 1 1/2), and decimals. Hours per day accepts partial hours, such as 0.5 for thirty minutes.
• Any number of appliances can be tracked at once, each producing its own totals while the combined totals reflect every entry.
• Settings holds the electricity rate in dollars per kWh (default $0.12, which approximates the US national average) and the number of days per month, adjustable for a billing cycle that differs from 30 days.
• Results show, per appliance, daily kWh, monthly kWh, daily cost, and monthly cost, followed by combined monthly and yearly totals.
• A step-by-step view, available in Settings, shows the conversion from watts to kilowatt-hours and the cost multiplication for each appliance.
• The core formula is: kWh per day = Wattage / 1000 x Hours per Day. Daily cost = kWh per day x Rate. Monthly cost = Daily cost x Days per Month. Yearly cost = Monthly cost x 12.

A 100 W device run 5 hours a day converts to kWh per day = 100 / 1000 x 5 = 0.5 kWh. At the default rate of $0.12 per kWh, daily cost = 0.5 x 0.12 = $0.06. Over a 30-day month that is 0.06 x 30 = $1.80, and across a year, 1.80 x 12 = $21.60.

Tracking electricity consumption at the appliance level reveals where most of a utility budget goes, making it straightforward to prioritize upgrades or adjust habits.

• Household budgeting: List every major appliance (refrigerator at 150 W running 24 hours, washing machine at 500 W running 1 hour, oven at 2000 W running 0.5 hours) to forecast the monthly electric bill and compare it against a budget target.
• Appliance comparison: Enter two versions of the same device (for example, an older 100 W incandescent bulb versus a 15 W LED replacement both running 8 hours a day) to see the annual savings from switching.
• Home office planning: Add a monitor at 30 W, a laptop at 65 W, a desk lamp at 10 W, and a router at 12 W, all running 10 hours per day, to estimate the incremental cost of working from home.
• Seasonal cost forecasting: Model summer cooling costs by entering a 1500 W portable air conditioner running 12 hours a day for a 30-day month, then compare against winter heating with a 1000 W space heater running 8 hours.
• Rental property management: Calculate baseline electricity costs for appliances included in a furnished rental (water heater, HVAC, refrigerator, microwave) to set a fair utility allowance for tenants.
• Solar offset analysis: Total household consumption in kWh per month, then compare it against the expected output of a proposed solar panel system to determine what percentage of the bill the panels would cover.
• Small business operations: Add commercial equipment (a point-of-sale terminal at 50 W, display signage at 200 W, a commercial refrigerator at 400 W) to forecast monthly electricity overhead for a storefront.