Electricity bills: base charge, tiered usage, and adjustments
A residential electric bill (Japan-style) breaks into several lines: base charge, usage charge, fuel-cost adjustment, renewable-energy surcharge. This article walks through what each is and how to estimate from appliance wattage.
Bill structure
A typical Japanese residential bill (TEPCO-style):
Bill = Base charge + Usage charge + Fuel adjustment + Renewable surcharge- Base charge — fixed, depends on contracted ampere capacity.
- Usage charge — variable, tiered by kWh consumed.
- Fuel adjustment — passes through fuel-price changes (positive or negative).
- Renewable surcharge — funds renewables build-out, paid by all consumers.
US bills are conceptually similar but typically simpler: a fixed monthly customer charge plus per-kWh rates that may or may not be tiered.
Base charge by amperage
TEPCO Energy Partner “Meter rate B” (2024):
| Contract | Base charge / month |
|---|---|
| 10A | ¥295.24 |
| 15A | ¥442.86 |
| 20A | ¥590.48 |
| 30A | ¥885.72 |
| 40A | ¥1,180.96 |
| 50A | ¥1,476.20 |
| 60A | ¥1,771.44 |
“Pay even if you use nothing.” Lower amperage saves money but trips the breaker more easily.
Tiered usage rate
TEPCO 3-tier (2024):
| Tier | Range | Rate (¥/kWh) |
|---|---|---|
| 1 | 0–120 kWh | 29.80 |
| 2 | 121–300 kWh | 36.40 |
| 3 | 301+ kWh | 40.49 |
More usage costs more per kWh — incentive to conserve.
300 kWh in a month:
120 × 29.80 + 180 × 36.40 = 3,576 + 6,552 = ¥10,128Fuel-cost adjustment
Reflects monthly imported-fuel prices (coal, LNG, oil):
Fuel adjustment = usage(kWh) × rate(¥/kWh)Rate changes monthly. Positive when oil is up, negative when down.
Example: +¥5.13/kWh:
300 kWh × 5.13 = ¥1,539 addedRenewable surcharge
“Renewable Energy Promotion Surcharge” — funds solar, wind expansion across all consumers:
Surcharge = usage(kWh) × rate(¥/kWh)FY2024: ¥3.49/kWh. 300 kWh → ¥1,047. Trending upward year by year.
Sample monthly bill
30A contract, 300 kWh used (TEPCO):
Base charge: ¥885.72
Usage charge: ¥10,128.00
Fuel adjustment: ¥1,539.00 (at +¥5.13/kWh)
Renewable surcharge: ¥1,047.00
────────────────────────────────
Total: ¥13,599.72About ¥13,600/month.
Estimating from appliance wattage
From “watts W” and “hours h” to “kWh”:
kWh = W × h / 1000A 1,500W hairdryer for 30 minutes:
1500 × 0.5 / 1000 = 0.75 kWhAt ¥30/kWh:
0.75 × 30 = ¥22.5Common appliance load
| Appliance | Power | Hours | Monthly cost @ ¥30/kWh |
|---|---|---|---|
| AC (cooling) | 600W | 8h × 30 | ¥4,320 |
| AC (heating) | 800W | 8h × 30 | ¥5,760 |
| Fridge | 100W | 24h × 30 | ¥2,160 |
| 55” TV | 200W | 4h × 30 | ¥720 |
| LED lights (room) | 50W | 6h × 30 | ¥270 |
| Microwave | 1500W | 0.5h × 30 | ¥675 |
| Hairdryer | 1500W | 0.25h × 30 | ¥337 |
| Standby (whole house) | 30W avg | 24h × 30 | ¥648 |
AC and fridge dominate. LED conversion and insulation pay off the most.
Standby power
Devices draw power even when “off” if plugged in:
- TV — 1–3W.
- Game console — 1–10W.
- Microwave — 1–2W.
- Router — 5–10W.
Whole-house standby costs ~¥600–1,000/month. Unplugging when away saves it.
Solar panel economics
Residential 4 kW system:
- Install — ¥1.0–1.5M.
- Annual generation — 4,000–4,800 kWh.
- Self-consumption + grid sales — ¥120,000–150,000/year.
- Payback — 8–12 years.
Feed-in tariff (FIT) rates have fallen each year. Combining with battery storage is now standard advice.
Time-of-use plans
Some plans charge less at night:
- Night (23:00–7:00) — discounted (~¥17/kWh).
- Daytime — premium (~¥30/kWh).
Good for all-electric homes (heat pumps, induction stoves). Bad for households with daytime work-from-home.
Reducing the contracted amperage
Going 30A → 20A saves ~¥295/month in base charge (TEPCO). About ¥3,540/year.
Tradeoffs:
- Limits simultaneous appliance use.
- More breaker trips.
- Switch is free (smart meter handles it).
Suits households that don’t run many appliances at once.
Choosing a plan
Options in deregulated Japan:
- Standard tiered — TEPCO Meter Rate B etc.
- All-electric — night-time discount.
- PPS retailers — ¥0 base charge, flat rates, varied pricing.
- Regional plans — time-of-use, point rebates.
Switching to a PPS often saves ¥10,000–30,000/year for a typical household.
High-impact savings
Ranked by typical effect:
- Adjust AC by 1°C — ¥2,500–3,500/year.
- Organize the fridge — ~¥2,000/year.
- Replace old appliances with efficient models — ¥5,000+/year.
- Switch to LED — ¥3,000+/year.
- Insulation / sealing improvements — ¥10,000–30,000/year.
“Turn things off” matters less than “use efficiently” or “buy efficient appliances.”
Summary
- Bill = base charge + usage charge + fuel adjustment + renewable surcharge.
- Usage tiers — rates rise with consumption.
- Fuel adjustment varies monthly.
- Major loads — AC and fridge.
- Formula — power(W) × hours(h) / 1000 = kWh.
To estimate monthly bills from appliance wattage, the electricity calculator on this site walks through the math.