For many landlords, a rental property is simply an asset that produces monthly income. It is advertised, a tenant moves in, rent is collected, and the cycle repeats.
That approach worked for decades. But today’s London rental market is more competitive, more regulated and more data-driven than ever, and landlords who manage passively leave real money on the table.
The most successful property investors no longer think like landlords. They think like business owners. And every business owner knows their numbers. These eight show your rental property performance at a glance.
8 numbers that measure rental property performance
1. Gross annual income
What it is: the rent or booking revenue you actually received over the last twelve months.
How to work it out: add up what arrived, not what was agreed. A £3,000 rent with a month’s void and a month of arrears is not £36,000; it is £30,000.
Why it matters: it is the honest starting point for every other number.
2. Net annual income
What it is: what is left after every cost of owning and running the property.
How to work it out: gross income minus service charge and ground rent, management fees, maintenance, insurance, compliance, void costs, and, for a short let, cleaning, platform commission and bills. Work it out before and after mortgage costs, because both tell you something.
Why it matters: two properties with the same rent can produce very different net incomes. In prime central London, a mansion-block service charge alone can absorb a fifth of a studio’s rent.
3. Occupancy rate
What it is: the share of the year the property was earning.
How to work it out: nights (or days) let, divided by nights available. A long let with two weeks’ void a year runs at about 96%. Across our own short-let portfolio, occupancy runs at around 80%.
Why it matters: occupancy is where most lost income hides. A few weeks of void each year can matter more than the rent you argued over.
4. Average daily or monthly revenue
What it is: for a long let, the effective monthly rent over the year, voids included. For a short let, two figures: the average daily rate (revenue divided by nights booked) and revenue per available night, or RevPAN (revenue divided by all nights available).
Why it matters: RevPAN combines price and occupancy in one number, which is why it is the right measure for a short let. A property charging £350 a night but empty half the month earns less than one at £250 a night that is nearly always full.
5. Operating costs
What it is: the total cost of running the property, ideally tracked as a percentage of gross income.
Why it matters: watching the percentage rather than the pounds shows you when costs creep up faster than income. In prime central London, costs commonly absorb 40% or more of a long let’s rent once a mansion block’s service charge is included, and more for a short let, which also carries cleaning, platform commission and bills. If the percentage keeps rising year after year, something is worth questioning.
6. Return on investment
What it is: how hard your money is working. Two measures are worth knowing: net yield (net income divided by the property’s price or current value) and cash-on-cash return (net income after mortgage costs, divided by the cash you actually put in, including purchase costs).
Why it matters: it lets you compare your property with other uses of the same money, including a different property, a different strategy or selling.
7. The cost of each vacant day
What it is: what one empty day costs you.
How to work it out: the daily rent (monthly rent × 12 ÷ 365) plus the daily share of the costs you pay regardless, such as mortgage interest, service charge, council tax and utilities.
Example: on a £3,000-a-month flat, the lost rent alone is about £99 a day. Add a typical London mortgage, service charge, council tax and bills, and an empty day can easily cost £150 or more.
Why it matters: once you know this number, decisions about price and speed become simple arithmetic. We cover it in depth in the real cost of a void period.
8. The lifetime value of a good tenant
What it is: the total rent a reliable tenant pays over their whole tenancy, set against what it costs to replace them.
Example: a tenant paying £3,000 a month for three years pays £108,000. Each change of tenant costs a void period, cleaning, decorating touch-ups, a new inventory and check-in, and the cost of finding and referencing someone new. It is easy for a single change of tenant to cost £4,000 or more.
Why it matters: it puts rent reviews in perspective. Pushing a good tenant out over a modest increase is often the most expensive decision a landlord makes.
Revenue matters more than rent
Many owners focus on the headline monthly rent. Businesses focus on annual revenue. Accepting £3,200 a month after an eight-week vacancy earns about £3,500 less in the first year than letting at £3,000 straight away. That is why the starting rent should come from what similar properties have actually let for, as our guide to how much rent to charge explains, rather than from the highest asking price on the street.
The same principle applies to short lets: a premium nightly rate that leaves the property empty underperforms a slightly lower rate with consistently high occupancy.
Adapt to the market
Markets change constantly. London demand moves with tourism, corporate travel, university terms, major events and the wider economy. Businesses respond to that; traditional landlords often do not.
Treating your property as a business means changing strategy when the numbers say so: a long-term tenant at one point, corporate or medium-term guests at another. That flexibility is the idea behind a hybrid letting strategy.
Time is money
Running a rental involves far more than collecting rent: marketing, photography, tenant and guest communication, maintenance, pricing, compliance, cleaning, booking management and financial reporting. Done inefficiently, each one costs money and creates stress. Like any business, having the right systems and experienced people in place improves performance and frees the owner to focus on the bigger picture.
Think beyond this month
Businesses do not measure success by a single month. Sometimes accepting a slightly lower rate today creates higher occupancy, better reviews and more income over the year. Sometimes delaying a tenancy to make improvements raises the rent for years to come. The best decisions are rarely the ones that maximise this month’s income. They are the ones that maximise long-term performance.
How we manage your property’s performance
At MX Lettings, we do not simply manage properties. We manage property performance. Every decision is guided by one question: will this improve your property’s annual return?
If you would like to know these eight numbers for your own property, we offer a free Property Performance Review. We will show you where the opportunities are and how to unlock your property’s full earning potential.