Solar Cooker Savings Calculator

How it is calculated

The tool multiplies four numbers. fuel per day = meals × fuel per meal, fuel saved per year = fuel per day × sunny days, saving per day = fuel per day × price and saving per year = fuel saved per year × price. meals is how many meals per day you cook with the sun, fuel_per_meal is how much fuel one such meal normally uses, in your own unit (kg, litres, kWh), price is the cost of one unit of that fuel in dollars, and days is the number of days a year the cooker is usable.

The fuel saved is shown in the same unit you used for fuel per meal, so a price per kilogram goes with a quantity in kilograms. Nothing can be negative. The calculation treats every sunny day identically and assumes the solar cooker fully replaces that fuel, with no backup use on cloudy days, no cost for the cooker and no allowance for slower cooking.

Common mistakes

• Counting all meals even though some cannot be cooked in the sun, such as breakfast before sunrise. Enter only the meals that really move to the solar cooker.
• Using 365 days. A solar cooker only works on sunny days, so use the number of days a year you can actually use it.
• Mixing units, such as fuel per meal in kilograms and price per tonne or per bag. The price must be for the same unit as the fuel quantity.
• Entering the price in local currency. The tool shows dollars, so convert the price to USD first for a meaningful money figure.
• Forgetting that the saving is gross. It does not subtract the cost of buying or building the cooker, so work out payback separately.