The Solo Shelf

Journal

The Single Tax: What a Household of One Pays

No government collects it, yet every person living alone pays it. Here is how it works, and where it can be cut.

By Kenneth McDonald · 15 November 2026

What does it cost to live alone, compared with living with one other person? The obvious answer is half. Two people share a home, so each pays half. The arithmetic of a real household does not work that way, and the gap between the two answers is what this essay calls the single tax.

Why two people do not cost twice as much as one

Statisticians who compare households of different sizes use a tool called an equivalence scale. The one most widely used by the Organisation for Economic Co-operation and Development and by Eurostat, the statistics office of the European Union, is the modified OECD scale. It gives the first adult in a household a weight of 1 and each additional adult a weight of 0.5. A two-adult household is therefore treated as needing 1.5 times the income of a one-adult household to live at the same standard, not twice as much.

The mechanism behind that 0.5 is shared fixed costs. A home has one front door, one kitchen, one fridge, one internet connection, one set of heating to run. Adding a second adult adds food and some wear, but the rent, the electricity standing charge, the broadband, the insurance and the television licence barely move. Split between two, each person’s share of those costs halves. Kept by one, the whole cost falls on one income.

On the modified OECD scale, each adult in a two-adult household needs 0.75 of what a person living alone needs. Put the other way round, the person living alone needs about a third more than each member of a couple to live at the same standard. On this scale, that third is the single tax. It is a model of what sharing saves on average, not a measured bill: a person in a cheap rented room may pay much less than a third more, and a person in an expensive city flat much more.

Where the single tax lands

The tax is not spread evenly. It concentrates in four places:

  1. Housing. Rent and mortgages are the largest fixed cost, and they scale with the home, not with the number of people in it. A one-bedroom flat does not cost half of a two-bedroom flat.
  2. Utilities and connections. Standing charges for energy, broadband and phone contracts are the same for one person as for two. In India, reporting by Onmanorama in August 2026 put a single occupant’s electricity and gas at about ₹2,000 a month, a bill halved the moment it is shared.
  3. Insurance and travel. Many policies are priced per household or per room. In travel, the “single supplement” charges a guest alone extra for a room priced for two.
  4. Pack sizes. Food and household goods are sold in family sizes. A person alone either pays more per unit for small packs or throws food away.

Researchers have begun to measure the effect in later life. The Society of Actuaries Research Institute in the United States published Impact of Family Structure on Aspects of Retirement (April 2026), a collection of essays including two on single-person households, which describe retirement systems built around couples and costs that people ageing alone carry by themselves. In Southeast Asia, Milieu Insight’s 2026 Solo Economy Study of 3,000 adults in Singapore, Malaysia, Thailand, Indonesia, the Philippines and Vietnam found that the cost of living alone is the main strain reported by people who do it.

Where the single tax can be cut

The single tax is a structure, and structures can be worked around. Each of the four places has a counter-move:

There is also a counter-weight that the arithmetic misses. Money spent by a household of one goes only where that one person chooses. No share of it is spent on compromise: on a holiday nobody fully wanted, a meal ordered for someone else’s taste, a subscription used by the other person. Professor Ming-Hsuan Lee of National Sun Yat-sen University in Taiwan, who has studied single consumers across Asia, has found that people living alone spend more on travel, dining and personal development, which is to say on investment in themselves.

Calculating your own

The single tax differs for every household, because rents, bills and habits differ. The Solo Shelf calculator at thesoloshelf.com uses a person’s own housing, bills, connections, insurance, subscriptions and food. It shows what they pay living alone and what each person would pay for the same standard in a two-person home, sets the result beside the equivalence-scale benchmark, and states its assumptions on screen. The difference is that person’s single tax, in their own currency, for their own life.

The question at the start was whether living alone costs twice as much or the same. On the standard scale the answer is neither: about a third more, concentrated in four places, and open to being cut in each of them. Each household’s own figure differs. Knowing the number is the first step to deciding what it buys.

Kenneth McDonald is the author of A Table for One and the forthcoming The Solo Shelf.

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