Electricity Cost Calculator
＋More features: add up several appliances at once
How much for the whole home? Up to six appliances at once
List the appliances you use most and you get the total electricity cost plus the share each one takes — so you can see which one is eating the power (the unit price comes from the form above; names may be left blank).
Enter an appliance’s wattage and the hours you use it per day, and you see what it costs per day, per month and per year. Amounts are in Japanese yen and the default unit price follows the guideline rate used for electricity bills in Japan, so it fits a Japanese electricity contract. Handy when you wonder what leaving the air conditioner or the kotatsu on really costs.
How to use
- Enter the appliance’s power consumption in watts (W). You will find it on the product label, in the manual, or on the manufacturer’s website.
- Enter how many hours a day you use it.
- The cost appears below as you type. You can change the unit price to the rate on your own contract.
How it is calculated
- Electricity used (kWh) = power (W) × hours used (h) ÷ 1000
- Cost = electricity used (kWh) × unit price (yen/kWh) (a month is counted as 30 days and a year as 365 days)
- The default unit price of 31 yen/kWh (tax included) is the “guideline unit price for electricity” (2022 July revision) set by Japan’s Fair Trade Council of the Electrical Appliance Industry (公益社団法人 全国家庭電気製品公正取引協議会). It is the official Japanese benchmark used for the running-cost figures printed on appliance catalogues in Japan.
- Example: a 500 W air conditioner used 8 hours a day → 4 kWh × 31 yen = about 124 yen/day (about 3,720 yen/month)
Sources (primary information)
- Fair Trade Council of the Electrical Appliance Industry (公益社団法人 全国家庭電気製品公正取引協議会), “Guideline unit price for electricity” (FAQ page), in Japanese
https://www.eftc.or.jp/qa/ (accessed July 18, 2026)
Assumptions and notes
- “Power consumption (W)” is the rated value. Inverter-controlled equipment (air conditioners, refrigerators) draws a different amount depending on how it is running. For a yearly estimate, the “annual power consumption (kWh/year)” figure printed on each product in Japan is also a useful reference.
- Standby power is not included.
Frequently asked questions
What if I only know the amperage (A)?
For a household outlet in Japan (100 V), you can estimate it as “power (W) ≈ 100 × current (A)”. The real power draw varies somewhat with the type of equipment.
How does this differ from the “annual power consumption” on the catalogue?
Annual power consumption (kWh/year) is a manufacturer’s measured value based on an assumed pattern of real use. For equipment whose output varies, such as air conditioners and refrigerators, “annual power consumption × unit price” is closer to reality.
Is it cheaper to leave it on or to switch it off often?
It depends on the equipment. Some devices draw a lot of power at start-up, so there is no single answer, but if you will not be using it for a long stretch, switching it off does reduce the energy used. Try comparing different hours with this tool.