Retrofit solutions via radio also make old apartments and houses smart.We show what options there are and how expensive smart lights, heating, etc. are.Not only those who spend a lot of time at home at the moment want to be comfortable at home.So it's great when technology contributes to the feel-good atmosphere.The keyword is Smart Home.In the first step, this means being able to control lamps, sockets, radiators or other building technology via app and voice - regardless of whether in the home network or on the go.However, a house only becomes really smart when it takes care of the crucial steps itself - and residents no longer have to worry about whether their toaster or iron is still connected to the electricity supply when they are on vacation.We explain which alternatives you can use to upgrade your own home to become a smart home.We also present the most important uses and the most relevant manufacturers and products.And, of course, what costs are associated with the increase in comfort in the smart home.How does a smart home actually work?The most important is a kind of nervous system that transports the switching signals to the components.For a long time there was nothing to avoid long cable routes.But now it is no longer necessary to rip open walls and lay cables.There have long been numerous good wireless solutions.In addition to the 2.4 gigahertz WiFi frequency band, the ZigBee and Z-Wave standards have established themselves for wireless transmission in the smart home.EnOcean, Bluetooth and DECT-ULE are also used less frequently.It remains to be seen how important the relatively young standard called Thread will be.In addition, many manufacturers cook their own soup and tailor a proprietary radio system around the 433 megahertz or 868 megahertz frequency ranges.All wireless options have their pros and cons.Two aspects are usually particularly important for beginners.Namely whether a gateway is necessary, i.e. a switch box that networks the wireless connection with the WLAN router.And whether the radio signal in the home can reach all components without the need for amplification from additional range extenders.The different power consumption of the radio standards, however, has become less important in recent years.Due to more economical and small radio chips, WLAN lamps in standby now also consume just as little energy as those with ZigBee.Once the components are networked, they can be controlled in different ways.Hardly any manufacturer does without an app that can be used to switch its own accessories on and off and to control their operating settings.It's also standard for smart home devices to accept voice commands from at least three major options: Amazon Alexa, Google Assistant, and Apple's Siri.And in some cases, a good old remote control is also available as an optional accessory.If you don't want to control everything by hand or tongue, you can automate the switching processes of the devices either with schedules or with routines that react to sensor signals.In particular, the combination of time, sensor values, weather and location factors enables very complex smart home scenarios with so-called if-then rules.For example, a motion detector can switch the light on when the occupants are present and activate the alarm when they are absent.And if you are not at home, the lighting can also be switched on and off automatically to simulate your presence.How easy it is to configure your own smart home system depends not only on the quality of the user interfaces, but above all on whether devices from different manufacturers can be integrated.If all components are of the same origin, they harmonize perfectly with each other in the best case.With a mix of several brands, the effort increases.Manufacturer-independent communication usually does not work without additional software.There are three options here.Smart home components can often be easily linked and operated together via cloud interfaces of commercial platforms such as Amazon Alexa, Apple HomeKit, Conrad Connect, IFTTT and Yonomi.However, if the Internet fails, the automatic rules stored on the web cannot find a recipient.Ambitious smart home users therefore let the threads come together on local mini servers such as a Raspberry Pi, which also remain operational offline.They control their setup with open source programs such as FHEM , iOBroker or openHAB , whose software maintenance depends heavily on the private commitment of a developer community.The advantages of the do-it-yourself solution are the lower costs and the far greater flexibility with regard to the choice of components and the setting options.A compromise are universal control centers such as Homee, Homey, Telekom Magenta, and Samsung SmartThings (test report), which enable mixed operation of cloud and local control.The selection of smart home components that can be used at home in the ways mentioned is now unmanageably large.The purchase no longer has to be expensive.However, it is not advisable to only pay attention to the price.How well a smart home system works in the long term depends heavily on the software substructure.If manufacturers do not cover the ongoing software maintenance through subscription income, they have to generate the costs through the sales price of the hardware.If you want to increase the probability that the products of your choice will be compatible with other standards and new applications for a long time to come, it is better to invest a few euros more.What does a Smart Home actually do?There are mainly three areas of application that justify the upgrade effort: save energy, more comfort, higher security.Those who use smart home components can reduce their energy consumption and thus protect the environment.This is done, for example, by switching off standby consumers, lamps and heaters when you are away, whereby the self-consumption of the smart components must be taken into account to be fair.In the best case, you can also save money.However, only after the purchase of the smart components has paid for itself.How quickly this works depends, among other things, on how disciplined the residents themselves are when it comes to switching off consumer devices that are not in use.The more forgetful they are, the more savings potential can be tapped with smart home technology.Much more decisive is the gain in comfort.Because that is definitely the case – regardless of whether the assignment pays off financially or not.Smart devices relieve the user of work.For example, networked thermostats set the temperature of the heating very cleverly and know in advance when the sun will heat up the living room because a web service provides them with weather data.The automatic dimming of the living room lighting or the lowering of the blinds when the television is switched on is also a possible scenario in which the smart home facilitates a feel-good atmosphere.Last but not least, a smart home can increase security or at least the subjective feeling of security in your own home.Networked surveillance cameras, video doorbells and sensors not only sound the alarm with a siren, but also push warnings directly to your own smartphone or to emergency contacts.If linked with smart light and smart door locks, the security technology can light the way in an emergency and guide helpers to the scene faster.In the following we describe in more detail what is possible with individual application areas such as smart light, heating, switching and monitoring.Smart lighting is a popular entry point into intelligent living.In many cases, to get started, it is sufficient to unscrew the old bulb from the socket and screw in the smart one.Not much more is necessary.With smart bulbs, you can easily create a cozy atmosphere with a simple command.In combination with smart motion detectors, the smart home switches the light on and off automatically.In addition, switching rules for wireless bulbs can help deter burglars and become aware of water leaks or smoke alarms more quickly.The range of networked light sources is very large.For basic lighting, there are LED lamps in many shapes for the sockets E27, E14 and GU10, occasionally also for GU 5.3 (12 volts).Alternatively, ready-made lights are available in various designs for table, wall, ceiling or cabinet mounting with built-in LEDs.For example, if floor lamps cannot be equipped with smart light sources because their housing is too small, they can be “smart” using radio-controlled sockets.Flexible LED strips or panels for wall and ceiling mounting are suitable as decorative mood lights.The top dog when it comes to smart light is the Signify group with its brands Philips Hue (test report) and Wiz.Under the umbrella of Ledvance, Osram's (Smart+ test report) former lighting division is to find its old form on the smart home market.Ikea gets involved with the Tradfri product range in the low-price segment.With Innr, Tint, Luminea and Eve, other European brands are vying for consumer favor.However, Chinese challengers such as Meross, Sonoff, Xiaomi and Yeelight would also like a piece of the pie and rely on an aggressive price war.Nanoleaf (Canvas test report) and Lifx are best known in North America, but are also popular with enthusiasts in this country.Here we have compared 5 E27 RGB bulbs with Zigbee.Lamps that can only display warm white are particularly cheap.At Ikea (Tradfri test report) it starts at 8 euros.For those that can vary between different shades of white, a small surcharge is due.RGB lamps, which can theoretically produce 16 million color nuances in addition to the white spectrum, are even more expensive.You can expect prices between 20 and 60 euros per lamp.Ready-made lights only start there and don't stop at over 400 euros.But the design also plays a major role here.The Hue Play Bars (test report) are comparatively cheap and more practical than design.The competition ensures more and more product alternatives in various areas of application.The suppliers are currently expanding their range of filament lamps with a filament look (filament lamps in comparison).In addition, more and more waterproof and dustproof decorative and ready-made outdoor lights are available that can be easily retrofitted.With many gadgets, the garden becomes an oasis of light and well-being.With the popular LED strips, ever finer controls make it possible to color diode clusters or even individual diodes.This allows new areas of application, such as the comparison of light color and brightness with the TV picture and music - for example with the Philips Hue Gradient Lightstrip.However, interested parties also need the Sync Box (test report) to control it.Depending on the manufacturer, the range also includes motion detectors, radio-controlled sockets, remote controls and radio-controlled switches for tables and walls.If you distribute several motion detectors in the apartment, you can completely do without light switches in extreme cases.Interested parties should first try out whether this really works in everyday life in a single room.If you prefer to operate your smart devices with a switch, you can easily retrofit them.Simple on and off switches, switches with a dimming function or color selection and multiple switches are available.Conventional light switches can be completely replaced with flush-mounted modules.However, they are not as easy to install as battery-operated wireless pushbuttons.You either stick these to the wall with double-sided pads like a normal light switch or place them on the table or sofa.What, sockets?Yes, apparently mundane sockets are actually top tips for getting started with the smart home.This allows older devices to be "made smart" that left the factory without a radio chip.Instead of the device itself, the radio plug can then simply be switched via app, voice or automatic.Color selection or dimming are then omitted.Networked adapter plugs are available in a wide variety of designs.Some models are small and unobtrusive, others are large, illuminated and have an additional USB port.Some adapters have a current sensor installed and are therefore also suitable for determining the power consumption.For example, the smart sockets switch the fan on or off via voice command, start the fan heater when entering the room or disconnect standby consumers from the mains when leaving the apartment.Practically all system manufacturers such as AVM, Bosch, D-Link, Eve, Fibaro, Gigaset, Innogy, Telekom Magenta, Samsung and Xiaomi and also more and more lighting specialists such as Philips Hue, Ledvance, Innr, Ikea, Tint and Wiz have at least one smart socket in their home Range.In addition, accessory specialists such as Brennenstuhl, Gosund, Koogeek, Meross, TP-Link, Vocolinc and more are represented in this area.Model selection in this category has particularly skyrocketed since Chinese platform supplier Tuya made its chips and control software available to resellers at low cost.You no longer have to spend more than ten euros for a no-name product.For models with many switching functions, weather protection, high power output and wireless range, 60 euros can also be charged.For a long time there were only networked single sockets.This may have prompted users to plug in many more consumer devices through intermediary power strips than the power of the smart adapter allows.Such dangerous adventures are no longer necessary.More and more manufacturers are now bringing smart sockets with two, three or four sockets onto the market for prices of up to 100 euros.Nevertheless, it can't hurt to pay attention to the usable overall performance.Voice control has given the smart home a boost in popularity.Above all, this affects the large services Amazon Alexa, Google Assistant and Siri from Apple.Telekom is trying to establish a German alternative with “Hello Magenta”.However, it currently plays a niche role in this country for the time being.In the smart home, the voice services mentioned can be operated particularly conveniently via loudspeakers whose built-in microphones offer a large recognition range.In addition to the smart home control itself, these so-called smart speakers also fulfill the classic function of playing music from streaming services such as Amazon Music, Apple Music, Spotify, Deezer and others.Some models have a multi-room function and play music synchronously on several speakers.To get you started, the providers have small smart speakers in their range at an affordable price.These include devices such as the Echo Dot (test report), Google Home Mini (Echo Dot and Home Mini in comparison), HomePod Mini and Telekom Smart Speaker Mini.Due to the limited sound quality, they are particularly suitable for voice control and as a kitchen radio replacement.Models with an audio output, such as the Echo Dot, can be connected to existing stereo systems using a jack cable.For better sound, there are more expensive speaker versions with more power.These include Echo Studio (all Echo models in comparison), Google Home Audio as well as Apple HomePod and Telekom Smart Speaker – the last two each without a suffix.Amazon and Google also license their voice services to audio specialists.Therefore, models like Sonos One (test report) or JBL Link 300 offer almost the same smart functions, but significantly better sound quality.Practical: The HomePod Mini has a thread hub, and the larger Echo models have a ZigBee gateway.No additional wireless bridge is then required for smart home devices that support these wireless standards.The speakers can take over the task right away.Controlling the temperature of radiators and underfloor heating using smart radio technology is another popular application for beginners.After all, the assembly is particularly easy to carry out and the effect can be felt immediately.Unscrew the old thermostat, screw on the new one - that's all it takes.In contrast to conventional models, smart thermostats are equipped with radio chips and an electric servomotor.Therefore, the controllers can be controlled remotely.And to the degree and not just roughly in five stages.An overview of our many individual tests on smart thermostats can be found here.Of course, the smart thermostats can be operated purely manually on the housing, via app or voice.However, it is much smarter to let them heat the smart home to a comfortable temperature using time schedules.So that the radiators do not heat for the street, all thermostats can be switched off automatically, for example when the window above them is open.Either the integrated software realizes this when the temperature sensor in the thermostat registers a sharp drop in heat.Or the thermostat reacts to a signal from a contact sensor that detects whether a window has been opened or closed.Corresponding contact sensors are often available as accessories.It is also practical if the smart controllers not only measure the temperature at the thermostat head, but also take into account the difference to the middle of the room.AVM, Gigaset and Tado offer accessories with temperature sensors that provide the thermostat with additional measured values ​​from any installation location.Another way to automate temperature control in the smart home is so-called geofencing.The control software uses the GPS coordinates of smartphones.When residents leave their home address, smart thermostats turn down the heating.As they get closer to home, the heater ramps up the temperature.Larger system providers such as AVM, Bosch, Eve, Fibaro, Gigaset, Innogy, Homematic IP and Magenta Smart Home also have thermostats in their range.Solutions that stand alone or can be integrated into platforms via a cloud interface come from Netatmo, Tado and Wiser, for example.Two new AA batteries are due at least every twelve or 24 months.In rare cases, fees for additional functions are added.Tado relies on this revenue model.Certain automatic functions are only available with a monthly subscription.Find out more in our Smart Heating guide.We have listed the best thermostats in our list of the best.Is there a more archaic need than feeling safe at home?It goes without saying that the smart home manufacturers are building on this.In addition to security in the sense of burglary protection, there are even more aspects associated with it.For example technology that warns of smoke gas, fire or escaping water.Appropriate sensors and monitoring devices were of course already in existence before there was any talk of smart homes.But networked safety technology offers additional advantages.Above all, a much more effective notification.Alarms can be pushed directly to a smartphone or smartwatch.In addition, residents can use an app to connect to the live stream of the surveillance cameras and in this way check from afar that everything is all right.In our guide to protection against twilight burglaries, we provide valuable information.And via automatic rules, the smoke detector not only switches on the siren, but also the smart light.This makes it easier to get out of the danger area at night.Motion detectors can launch smart lights to simulate presence if someone is moving outside at unusual times.Speaking of inside and outside.The young category of video doorbells provides more control in the access area.They are basically a logical development of surveillance cameras, only with a bell function.When the doorbell rings, the smartphone can be used to call up the video image and check whether it is really worth opening the door.It also helps smart home residents avoid missing an important parcel delivery.When it comes to not only monitoring doors, but also opening or locking them automatically, smart locks are an option.You replace the conventional front door lock with one with an electric motor and Bluetooth connection.Residents can use a switching signal to open them for the emergency doctor, nursing staff or for normal visits if they are unable to get to the door themselves.Smart locks also come in handy when approaching the front door with grocery bags in both hands.If activated, smart locks react to the approach of the smartphone to the home address and unlock the lock by itself.Those arriving then only have to lean against the ajar door leaf and do not have to put their luggage down first.Motion sensors, contact sensors for doors and windows, and alarm sirens are part of the standard repertoire of most smart home system manufacturers.Either own-brand surveillance cameras are included or third-party models can be integrated via an interface.Camera models from accessory specialists such as Arlo, Netatmo and Ring can be connected on a broad level.They also have video doorbells in their range.Providers such as Egardia (test report) or Lupus concentrate on complete alarm systems.However, monitoring your own four walls is not entirely trivial, which is why we deal with alarm systems in a separate article.The champion of smart locks is Nuki (test report) .Other brands specifically from the smart home sector are Danalock and eQ-3.The internationally well-known Yale brand has also been more active in Germany since this year.As a challenger, Tedee wants to secure a place in German smart homes.Smart locks are also available from traditional providers such as Abus and Burg-Wächter (test report).A comparison of secure smart locks can be found here.According to official sources, the average living space in Germany is about 45 square meters.For our sample calculation, we assume a total of five rooms: kitchen, bathroom, hallway, bedroom and living room.We equip all rooms with an RGBW lamp for the E27 base and a smart socket.Two motion sensors in the hallway and kitchen and three light switches in the other rooms are used for control.For voice control, we use a large Alexa speaker and a ZigBee gateway in the living room, as well as a small Alexa speaker in the kitchen and bathroom.In addition, we are giving the model apartment a smart doorbell with a camera, two radiator controls and two temperature sensors.When making the selection, we made sure that everything is really compatible with each other - be it via ZigBee or Alexa.In order to calculate a realistic final price, we did not use any special offers or set offers, but only used the starter kits or individual prices from the price comparison.The Pearl brand Elesion (test report) and Xiaomi Aquara (test report) allow a particularly cheap entry into the smart home world.Smart home components make everyday life easier and can save operating costs.If you take your time planning and use the price comparison, you can save a lot on the purchase.However, if you buy as cheaply as possible, you have to rely on a large number of different manufacturers, which makes programming more complicated.In order to network different brands properly, we recommend Alexa or HomeKit for beginners, Conrad Connect or one of the open source systems for ambitious users.If the combination of different standards seems too complicated for you, you should concentrate on one or two manufacturers and use ready-made sets.However, the costs are far higher than with a mix of devices.In addition, users are then always dependent on what one manufacturer has to offer and may have to do without other functions.Detailed information on the subject can be found in the smart home cover story of c't 8/2020.- The links marked with are commission links (affiliate links).If an order is placed via such a link, TechStage receives a commission.This does not result in any additional costs for the buyer.