Most smart home guides are written for homeowners. This one is not. If you rent in Germany — which around 60 percent of the population does — you are working within legal constraints that most guides simply ignore.
The legal starting point
Under Mietrecht, the German tenancy law, any modification that alters the substance of the rental property requires landlord permission. This covers anything involving drilling, permanent installation, modification of electrical fittings, or changes to plumbing. The scope is broader than you might expect. What it does not cover: furniture, freestanding devices, and anything that leaves no trace when removed.
The practical implication is that most smart home setups are possible without landlord permission, as long as they do not require permanent installation. The exceptions are things like built-in smart door locks (which require modifying the door), hardwired sensors, or replacing existing switches and sockets with smart equivalents.
Lighting
Smart bulbs in existing fixtures are entirely fine — you are replacing the bulb, not the fixture. Philips Hue and the IKEA TRADFRI system both work well in Germany and have local control options (important for privacy and for situations where you do not want to depend on a cloud service). The TRADFRI hub communicates via Zigbee rather than Wi-Fi, which keeps it off your main network.
Smart plugs between a lamp and the wall socket are also straightforward. What gets complicated is if you want in-wall smart switches, because that involves accessing the electrical box behind the switch, which is a modification. Some people argue that a reversible swap does not require permission; the safer position is to ask, especially given that German landlords tend to document apartment condition in some detail.
Heating
Smart thermostatic radiator valves (TRVs) are the most Germany-specific smart home question. The radiators in most German apartments use the standard Euroconus thread, and smart TRVs like the Homematic IP or Fritz!DECT 301 screw on in place of the existing valve head without modifying anything. The old valve head goes in a drawer and goes back when you move out. This is well-established as not requiring landlord permission.
Be aware that Homematic IP has a fairly functional local control option, while many cheaper TRV brands require a cloud account. Given that these devices are controlling your heating and therefore your heating bill, local control is worth the additional cost.
Security and monitoring
Indoor cameras and motion sensors placed as freestanding units are allowed — you are putting furniture in your apartment. Fixed cameras mounted to walls or ceilings require drilling. Door sensors using adhesive strips rather than screws are generally accepted as non-permanent, though some adhesive leaves marks.
The more relevant German-specific concern with home cameras is neighbour privacy. Germany has strict rules about cameras that capture shared spaces or neighbouring apartments. A camera covering your front door from inside your apartment is fine. A camera pointing into a shared corridor is legally problematic. This is not a Mietrecht issue, it is a separate privacy law issue.
Home assistants and hubs
Voice assistants (Amazon Echo devices are widely available in Germany; Google Nest; Apple HomePod) have no installation issues — they are freestanding. The matter of what data they send where is a separate topic. Locally hosted options like Home Assistant running on a Raspberry Pi are popular in Germany's technically inclined expat community, partly because they avoid any third-party cloud dependency.
Moving out
When you leave a German rental, you are expected to return it in the condition it was in when you arrived (minus normal wear). Smart devices that are fully freestanding and removable are not an issue. If you have used adhesive hooks or strips anywhere, remove them carefully — the question of whether they leave marks is taken seriously in German Übergabeprotokoll (handover inspection) procedures.
If you have done anything that required permission and got it in writing, keep the written permission — you will want it at handover to document that the modification was agreed.