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Managing Your Electricity

Author: Paul Granberg, Issue: October 2004, Topic: Household

Most average Western homes have a 100 - 200 ampere (A) connection to the national grid. However, with most Japanese homes, this connection averages around the 20A mark.

What does this mean for me?

Simple, you can run very few electrical appliances simultaneously. Too many, and you'll have a miniature 'black-out' in your apartment until you can re-set your circuit breaker.

So how many can I run?

It depends on two factors.

1) How 'big' is your connection?

Have a look at your circuit breaker box. (The main power switch). The colour of this box tells you what the capacity of your connection is.

  • 15A Pink Circuit Breaker
  • 20A Yellow Circuit Breaker
  • 30A Green Circuit Breaker

Work out your electrical load budget.

100v (Ibaraki's voltage)
Amperage (your circuit breaker colour)
Your electrical budget in 'Watts'

The average apartment has a 20 Ampere (yellow) circuit breaker.

So the average electrical load 'budget' would be
100v X 20A = 2000 Watts

So you have 2000 watts to run your apartment on.

2) What appliances you are running?

Different kinds of appliances place different loads on you electrical system. Here's a rough guide as to how much energy different appliances use. (Assumes they are functioning at full power)

  • Air conditioner 1,000w (1kWh)
  • Electric Heater 1,000w (1kWh)
  • Hairdryer 800w (.8kWh)
  • Microwave 800w (.8kWh)
  • Kotatsu 500w (.5kWh)
  • TV 150w (.15kWh)
  • Laptop 90w (.09kWh)
  • 1 large Fluro Tube 40w (.04kWh)


(As at 25/7/03)

Basic Monthly Connection Charge

  • 15A Pink C/Breaker --- 390 yen per month
  • 20A Yellow C/Breaker --- 520 yen per month
  • 30A Green C/Breaker --- 780 yen per month

Price per kWh of Electricity

  • (kWh is 1,000 watts for one hour)
  • 0 - 120 kWh --- 15.58 yen per kWh
  • 121 - 300 kWh --- 20.67 yen per kWh
  • 301+ kWh --- 22.43 yen per kWh


  • I have a 20A (Yellow C/Breaker) connection to the power grid.
  • I use 200kWh per month of electricity.
  • 200kWh x 20.67yen per kWh = 4,134 yen
  • Connection charge = +520 yen
  • MONTHLY TOTAL 4,654 yen

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