Warmmiete and the Mietspiegel: Why Only Cold Rent Counts When Comparing

Try to compare your own rent against the local Mietspiegel (rent index), and you'll quickly run into a common mix-up: the Mietspiegel never rates your Warmmiete, only your Nettokaltmiete. Miss that distinction, and you end up comparing the wrong numbers.

What the Mietspiegel actually measures

The ortsübliche Vergleichsmiete (local comparative rent) that underlies the Mietspiegel always refers, under § 558 BGB, to the Nettokaltmiete — the pure apartment rent, excluding operating costs and heating. It's calculated from the average of rents newly agreed or changed for comparable apartments in a municipality over the past six years.

Why Warmmiete doesn't work for comparison

Warmmiete is made up of the Kaltmiete plus an individual Nebenkosten prepayment, which varies significantly depending on the building, heating type, and consumption. Two apartments with an identical Kaltmiete can therefore have very different Warmmiete figures, depending on whether one is a renovated new build and the other an older, unrenovated building with high heating needs. If the Mietspiegel used Warmmiete instead, differences between buildings would wrongly get attributed to the rent level itself.

How to correctly compare your own rent

To compare your own rent to the Mietspiegel, first subtract your Nebenkosten advance payment from your Warmmiete to arrive at the Nettokaltmiete. Only that adjusted figure, divided by your apartment's floor space, can meaningfully be compared to the per-square-meter price the Mietspiegel lists for your specific location and building category.

Why this matters for a possible rent increase

If a landlord demands a rent increase up to the local comparative rent, that increase can also only be based on the Nettokaltmiete, not the Warmmiete. A demand that instead starts from the Warmmiete is calculating from the wrong baseline, and can be challenged on that basis.

What this means when comparing listings during your search

Apartment listings are often advertised with only the Warmmiete shown. For a fair comparison against the local rent level, it's worth specifically looking for the Kaltmiete listed in the ad, rather than relying solely on the Warmmiete, which depends heavily on that particular apartment's individual Nebenkosten share.

For a deeper look at how Kaltmiete, Warmmiete and Nebenkosten relate to each other, and the three pricing models landlords use, see our guide on Nettokaltmiete vs. Bruttokaltmiete vs. Inklusivmiete. And if you're not sure whether your Nebenkosten advance payment itself is reasonable, our guide on how high Nebenkosten can legally run explains what to check.

Frequently Asked Questions

Does the Mietspiegel refer to Warmmiete or Kaltmiete?

Only to the Nettokaltmiete, under § 558 BGB. Nebenkosten and heating are excluded from the comparison.

Why is Warmmiete unsuitable for comparing rents?

Because it depends heavily on individual factors like building condition and heating consumption, which have nothing to do with the actual rent level.