The electricity bill arrives, the amount doesn't match the perceived usage, and the argument at home begins about who left what on. Almost always, the fight is about the wrong target: the significant expense doesn't come from what people remember using, but from a few appliances that consume energy silently—some of them running twenty-four hours a day.
No guesswork required. There's a simple calculation that translates the cost of each appliance in your home to your monthly budget. This guide shows you the formula, applies it to each appliance, and ends with a list of what you can change today.
The formula
Every appliance has its wattage rating on the label or in the manual. From that information:
(watts × hours of use per day × 30) ÷ 1,000 = monthly consumption in kWh
Next, multiply the result by the price per kWh. And here's the part that determines whether the calculation is valid or not: Use the price printed on your invoice.. The rate varies by distributor, by state, and by the tariff flag of the month.
For reference, the average residential tariff in the country is around R$ 0.85 per kWh — but the difference between the most expensive and the cheapest distributor is over twenty cents, and there are states with averages well above that. The regulatory agency projected an average increase of around 8% for 2026. The examples below use R$ 0.85; recalculate with your own number.
Electric shower
It is the highest installed power of a typical house: between 4,000 and 8,000 watts, depending on the resistance and position of the key.
A family of four taking 15-minute showers daily consumes approximately 120 kWh per month That alone — around R$ 100 in the example tariff, which in many households represents 20% to 30% of the entire bill.
What solves the problem: always use the warm setting whenever possible, because the heating element works at reduced power and consumption is halved. And shortening your shower from 15 to 10 minutes cuts about 30% from the shower's consumption, without any loss.
Air conditioning
A typical window device pulls between 1,000 and 1,500 watts in operation. Eight hours a day in the summer gives them 240 to 360 kWh per month — something between R$ 200 and R$ 300 in the example tariff, only in that item.
Older models consume considerably more energy than current models with good efficiency ratings, and this difference shows up on the bill every summer month.
The setting that yields the best return is temperature: Raising the temperature by two degrees reduces consumption by approximately 10%.. A clean filter also matters, because a dirty filter forces the compressor to work harder for the same cooling.
Refrigerator
Proof that isolated power consumption can be deceiving. The refrigerator uses between 400 and 800 watts, well below the shower — but it works. All year round, without switching off..
A typical model consumes of 100 to 200 kWh per month. Older appliances exceed 300 kWh due to less efficient motors and worn-out seals.
What reduces costs: a good sealing rubber, keeping the appliance away from the wall, away from the stove and direct sunlight, and keeping the door open as little as possible. Simply repositioning it to a cooler corner of the kitchen saves close to 15%.
It's also where switching to an efficient model pays for itself faster, precisely because consumption is continuous.
Washing machine
Consume between 2,000 and 3,500 watts during the cycle. With three to four washes per week, it stays between 30 and 50 kWh per month.
What matters here is habit, not the machine: washing full loads instead of washing small amounts of laundry several times reduces the number of cycles, which is what counts. An economy cycle for lightly soiled clothes and washing in cold water are also important.
Television and on-demand consumption
A 50-inch TV uses between 80 and 150 watts when switched on. Five hours a day adds up to approximately... 15 kWh per month — very little, compared to the rest.
What gets overlooked is standby mode. Devices switched off via remote control continue to consume power: a cable TV receiver can draw 15 to 20 watts continuously, the same as an LED light bulb left on day and night.
In a house with a TV, receiver, stereo, microwave with clock, and chargers plugged into the wall, the total consumption usually ranges between 50 and 100 kWh per month. It's not the biggest culprit, but it's the easiest to eliminate: a power strip with a switch solves the problem.
Iron, electric oven and dryer
All high-powered and short-term use. Irons between 1,000 and 2,000 watts, hair dryers between 1,500 and 2,000 watts, electric ovens that can exceed 2,000 watts.
Since usage is intermittent, the total monthly cost is usually modest—unless the frequency is high. Ironing all the clothes at once, with the iron already heated, is more efficient than turning it on and off several times a week.
How to find your villain in ten minutes.
- Take the bill and note the total monthly consumption in kWh and the price per kWh.
- List the high-power devices.Shower, air conditioner, refrigerator, washing machine, oven.
- Estimate usage hours From each one, honestly.
- Apply the formula in each item.
- Add and compare with the total bill. If it was close, you found those responsible. If it was much lower, there was hidden consumption—usually waiting, an old refrigerator, or some appliance left on.
What changes the bill later this month?
- Shower on warm setting whenever the temperature allows.
- Air conditioning two degrees higher more than usual.
- A shower five minutes shorter.
- Power strip with switch inside the TV set, switched off at night.
- Keep the refrigerator away from the stove., with sealing provided.
- Laundry done with a full load and in cold water.
- Old light bulbs replaced with LEDs, If it still exists.
Common questions
Shower or refrigerator: which consumes more energy?
High power and short usage versus low power and uninterrupted use. In typical calculations, the two compete for first place, and the result depends on the size of the family and the age of the refrigerator.
Does a charger plugged into an outlet use energy?
It consumes very little energy, almost negligible on its own. The habit of removing it is more worthwhile for safety and the lifespan of the charger.
Does the tariff flag significantly affect the price?
Change. The flag represents an additional charge per kWh based on the month's generation conditions. Under the red flag, the same consumption costs more.
Is it worth replacing an old refrigerator?
This is usually worthwhile for very old appliances. Compare the estimated energy consumption of the new model with your current one and see how many months it takes for the difference to cover the price.
Does the efficiency label make a difference?
It does, and the longer the appliance is on, the greater the return. For refrigerators and air conditioners, this is the most important information to consider when buying.
Does an app to measure consumption solve the problem?
An app that only estimates does what you can do yourself with the formula. A real measurement requires a wall outlet meter, which is inexpensive and eliminates the need for a specific device.
Summary
Take your bill, check the price per kWh, and apply the formula to the four most powerful appliances in your house. In ten minutes, you'll trade feeling for numbers—and discover that, in most Brazilian homes, the battle for first place is between the shower and the refrigerator.
