See how many kWh an appliance uses a month and what it costs in reais — right in your browser.
Electricity is billed by the kilowatt-hour, and a kilowatt-hour is simply one thousand watts kept running for one hour. That makes the calculation short: multiply the power of the appliance in watts by the hours it runs each day and by the days in the month, then divide by 1,000 to get kWh. An electric shower of 5,500 W used half an hour a day for thirty days consumes 82.5 kWh a month; at a tariff of R$ 0.95 per kWh that is R$ 78.38 a month, or R$ 940.50 a year. The tool shows the kWh, the monthly cost and the yearly total together, because the yearly figure is usually the one that changes behaviour.
The surprising part is how power and time trade against each other. The shower is one of the highest-wattage things in a Brazilian home and still costs less than an air conditioner that draws a fifth of the power but runs eight hours every night. A phone charger left plugged in all year is a rounding error; a second fridge in the garage is not. Two cautions on the input: motors that cycle — fridges, freezers and air conditioners — only draw their rated power part of the time, so multiplying the nameplate watts by twenty-four hours overstates them by two to three times, while appliances with a heating element, such as ovens, kettles and hairdryers, sit close to their rated draw whenever they are actually on.
The tariff is the input worth getting right, and the one nobody knows by heart. It varies by distributor, by consumption bracket and by the tariff flag of the month, and the figure that matters is the one that already includes taxes. The quickest way to find it is on the bill itself: divide the total charged by the kilowatt-hours billed, or read the R$/kWh line directly. The R$ 0.95 loaded by default is a plausible Brazilian average and nothing more — replace it with yours before trusting the reais. All the arithmetic happens in your browser, so nothing about your home, your appliances or your bill is sent anywhere.
kWh per month = (power in watts × hours a day × days a month) ÷ 1,000. Monthly cost = kWh per month × tariff in R$/kWh, and the yearly cost is that figure multiplied by 12. The always-on mode uses 24 hours a day over 30 days.
Multiply its power in watts by the hours it runs a day and by the days in the month, divide by 1,000 to get kWh, then multiply by your tariff. A 5,500 W shower used 30 minutes a day for 30 days uses 82.5 kWh — R$ 78.38 at R$ 0.95 per kWh.
On the label or plate of the appliance, usually next to the voltage, and in the manual. If only amps are shown, multiply amps by the voltage: 10 A at 127 V is 1,270 W.
The one on your own bill, taxes included. Divide the total charged by the kWh billed, or look for the R$/kWh line. Tariffs differ by distributor and move with the tariff flag of the month, so the default value here is only a placeholder.
Because its compressor switches on and off. Fridges, freezers and air conditioners only draw their rated power part of the time, so counting all 24 hours at full watts overstates them — a modern fridge usually lands around 30 to 45 kWh a month.
No. The power, the hours and the tariff are used locally in JavaScript on your device, and no data about your consumption is transmitted or stored.
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