May 7, 2026
By the HalfKey team
The kōnetsuhi flat fee, decoded with real kWh math
Most Tokyo monthly furnished listings show one utility line: 光熱費, ¥10,000 to ¥18,000 per month, flat. That number is a bet by the operator about how much electricity, gas, and water you will use. Sometimes you win the bet. Often you lose it. The math is small but it is not zero.
Open three Tokyo monthly furnished listings on Suumo or GaijinPot Apartments. Look at the utility line. You will see 光熱費 (kōnetsuhi — "light-and-heat fee," the bundled utility line).
It covers electricity, gas, and water as a single flat number. The amount is usually ¥10,000, ¥12,000, ¥15,000, or ¥18,000. It is almost never itemized.
It is almost never metered to your specific stay. It is a price the operator picked.
So what is the operator actually betting on, and when does the bet land in your favor.
Start with what a Tokyo studio actually consumes. A 22m² 1K with one occupant runs about 150 kWh of electricity per month in spring and fall. In summer the aircon load pushes that to around 220 kWh.
Mid-winter heating, plus the lower outdoor temperature making the heat pump work harder, lifts it to 280 or 320 kWh.
Tokyo Electric Power Company (東京電力, TEPCO) prices residential electricity on the 従量電灯B (jūryō dentō B — "metered lighting B"). The tariff has three usage tiers.
At 2026 rates: ¥30 per kWh for the first 120 kWh. ¥36 per kWh from 121 to 300 kWh. ¥40 per kWh above 300 kWh.
Add a basic monthly charge of around ¥1,000 for a 30A connection. Add the renewable-energy surcharge of about ¥3 per kWh. Round to ¥35 per kWh all-in for a typical apartment month.
Gas for a single occupant in a unit with a gas water heater runs ¥3,000 to ¥6,000 per month, depending on bath frequency. Water in Tokyo on a single-occupant residential meter is roughly ¥2,500 per month including sewage. Set those aside and assume the operator covers them inside the same flat fee.
So the all-in metered cost looks like this:
- Spring or fall (April, May, October): 150 kWh × ¥35 = ¥5,250 electricity, plus ¥4,000 gas, plus ¥2,500 water. Total: ¥11,750.
- Summer (July, August): 220 kWh × ¥35 = ¥7,700 electricity, plus ¥3,500 gas, plus ¥2,500 water. Total: ¥13,700.
- Mid-winter (January, February): 300 kWh × ¥35 = ¥10,500 electricity, plus ¥5,500 gas, plus ¥2,500 water. Total: ¥18,500.
Now compare to the typical operator flat rate.
Most operators in the 1-to-6-month furnished segment charge ¥12,000 or ¥15,000 per month, year-round. A few of the higher-end serviced apartment brands charge ¥18,000.
Almost none vary the fee by season. Run the comparison.
A tenant booking a ¥12,000 flat-fee unit in October pays about ¥250 more than the metered cost would have been. That is the operator's small margin in a low-usage month.
The same tenant in August pays roughly ¥1,700 below the metered cost. The operator subsidizes the summer.
The same tenant in January pays ¥6,500 below the metered cost. The operator subsidizes hard in winter.
A tenant booking a ¥15,000 flat-fee unit in October pays ¥3,250 above metered cost. In August: ¥1,300 above. In January: ¥3,500 below.
The break-even season for the operator is roughly summer. Spring and fall are the operator's profit window. Winter is the operator's loss window.
A tenant on a ¥18,000 flat fee is over-paying nine months out of twelve. The win comes only in the depths of winter.
That bracket usually prices for buildings with leaky heating. Or it prices for operators who absorb winter risk by collecting a premium year-round.
Why bundle at all. The operator could meter every unit individually and charge actual usage.
Some do. Most don't. The reason is administrative cost, not pricing.
TEPCO issues contracts per-meter and requires the contract-holder's name and bank account. If the operator holds the master lease, the operator's name is on every meter.
Passing actual usage through to a 60-day guest is real work. The operator must read the meter at check-in. Read it again at check-out.
Multiply the difference by a tariff with three tiers. Divide proportionally when the billing cycle straddles the stay. Send an itemized invoice in English, then field the inevitable disputes.
For a unit producing maybe ¥15,000 of electricity revenue per month, that load eats most of the margin. The flat fee is the operator paying themselves a small premium to never do that work.
There is also a behavioral reason. Metered tenants run aircon less. Operators noticed.
They did not love the resulting reviews ("the apartment was hot," "I was scared to use heating"). The flat fee removes the disincentive to use the climate control the building already advertises.
Where the bundling actually hurts you: a single occupant on a 30-day October stay. They barely cook, take short showers, and leave the unit empty during work hours.
Real metered usage might be ¥7,000. The flat fee is ¥15,000. You are over-paying by ¥8,000 on a stay where the rent is ¥150,000.
That is 5% of the headline rent. Small, but real money the operator collected for nothing.
Where it helps you: two occupants on a 30-day stay in February. They run heating most of the day, and they take long baths.
Real metered usage might be ¥22,000. The flat fee is ¥15,000. The operator absorbed ¥7,000 of cost.
You won that month.
If you are choosing between two otherwise-identical units, look at how each one prices utilities. One charges a ¥12,000 flat fee. The other meters you.
The metered option saves you money in shoulder seasons (April, May, October). It costs you money in winter.
The flat fee is the safer pick if you cannot predict your own consumption. It is the worse pick if you will be away from the apartment most days.
The next time you compare two listings: write the kōnetsuhi number down and check what month you arrive. ¥15,000 in October is the operator's profit. ¥15,000 in February is your subsidy.
The flat fee is not a service charge. It is a year-rounded price on a usage curve that is anything but flat.