Formulas, worked examples and checklists. Every number is a labelled assumption.
How to add up purchase price, running costs and expected lifespan into a cost-per-year figure, with a worked example where the cheaper product loses.
A simple formula for turning an appliance wattage and daily usage into a monthly electricity cost, with worked examples and caveats about tiered rates.
What standby (vampire) power is, how to convert it into a monthly cost with a worked example, and practical ways to reduce it.
A refrigerator runs 24 hours a day, so its labelled yearly energy use tells you the running cost. Here is how to convert it and compare two models.
How to read yearly energy cost on an appliance label and work out the payback period of a more efficient, more expensive model.
How to calculate the monthly cost of running an electric space heater from its wattage and daily hours, plus when it makes sense versus heating a whole home.
How to compare the electricity and water cost of a dishwasher load with handwashing, with the heating-water physics behind the numbers.
How to calculate yearly running cost and payback time when swapping an incandescent bulb for an LED.
How to calculate the real cost per cup of a pod coffee machine by spreading the machine price over its life, and how to compare it with other methods.
Air purifier filters are the main running cost. How to convert filter price and replacement interval to yearly cost and compare two models over five years.
Simple arithmetic for how many months it takes to save for a large purchase, and how a sale discount changes the timeline.
How to estimate yearly electricity savings of a heat pump dryer versus a standard dryer and the payback period against its higher price.
How to convert filter price and capacity into cost per gallon and per year, with a worked example comparing two kinds of filtration.
How to decide whether an extended warranty or protection plan is worth buying by comparing its price to the expected repair cost.
Monthly rental prices hide the total. How to compute total rental cost and what to check about fees, ownership, servicing and early termination.
How to compare a used and a new appliance by cost per year of expected use, with a worked example and a short inspection checklist.
A checklist for measuring the space, door swing, delivery path and connections before buying a large appliance so it actually fits.
Cordless vacuums have a battery that wears out. A worked cost-per-year comparison of corded and cordless models, including battery replacement.