Intelligent Building Technology (Lexikon) – Controlling the House via Smartphone, Saving Electricity & the Trend of the Future
Smart building technology is no longer just a toy for tech enthusiasts — it has become a hard return factor. While a conventional apartment building today yields a gross return of 4–6 %, smartly equipped properties can achieve 0.3–0.8 percentage points more rental return and 5–12 % higher resale prices, depending on the location. At the same time, energy costs decrease by 15–30 %, which becomes an argument during the additional costs calculation and marketing. This lexicon entry explains what smart building technology economically means for investors, how you can optimally reflect the investment tax-wise, and from which point the additional cost actually pays off.
Definition: What exactly does smart building technology include?
Smart building technology (also known as Smart Building or Smart Home) refers to the electronically networked control of all technical trades of a property via a central platform. The systems range from simple radio solutions to KNX-based bus systems that are integrated into the electrical installation and make the property technically future-proof for 15–20 years.
- Heating & Climate — Room-specific control, heat pump control
- Lighting — Presence, daylight and scene control
- Shading — Blinds, shutters, awnings weather-dependent
- Security — Access, alarm, video surveillance, water detectors
- Energy — PV, storage, wallbox, load management
- Comfort — Multimedia, voice control, scenes
For investors: Smart home components are not just a comfort investment, but directly affect the energy efficiency class, rentability and thus the market value. Anyone acquiring a property should include the Rating of the technology in the property valuation logic.
Investment costs: What does a smart home upgrade really cost?
The cost spread is enormous — and this is exactly where the leverage lies. A retrofitted radio solution in an 80-m² apartment starts at 2,500 €, while a fully integrated KNX system in a new-build villa can exceed 80,000 €. For the investment calculation, the additional cost per m² that you have to add to the purchase price or construction costs is relevant.
| Ausbaustufe | Aufpreis €/m² | Beispiel 100 m² | Energy savings per year | Mietaufschlag |
|---|---|---|---|---|
| Base (heating, heating + light) | 30–60 | 3.000–6.000 € | 10–15 % | 0,20–0,40 €/m² |
| Comfort (KNX, shading, security) | 120–200 | 12.000–20.000 € | 20–25 % | 0,50–0,90 €/m² |
| Premium (Vollintegration + PV/Speicher) | 250–450 | 25.000–45.000 € | 30–50 % | 1,00–1,80 €/m² |
Before every decision, it’s worth looking at the
Return calculation: Three scenarios for investors
What matters is not the premium, but what it brings you. We compare a classic apartment building (8 apartments, 600 m² living space, purchase price 1.8 million €) without, with comfort and with premium smart home equipment.
| Key figure | Conventional | Comfort Smart | Premium Smart |
|---|---|---|---|
| Purchase price / investment | 1,800,000 € | 1,890,000 € | 2,010,000 € |
| Annual cold rent | 86,400 € | 91,800 € | 97,200 € |
| Gross yield | 4.80 % | 4.86 % | 4.84 % |
| General energy costs per year | 9,600 € | 7,700 € | 5,300 € |
| Value increase after 10 years (estimate) | +22 % | +28 % | +34 % |
| Vacancy risk | medium | low | very low |
The gross yield only shifts marginally — the real lever is in the value increase and the security of rental income. Detailed calculations are provided by the
Tax Treatment: Depreciation, Maintenance Costs or Construction Costs?
This is where it gets legally tricky for rental investors — the classification determines whether you can deduct your smart home investment immediately or over 50 years. The tax office strictly distinguishes between three categories, regulated in § 6 EStG, § 7 EStG (depreciation) and § 255 HGB:
- Maintenance costs (§ 21 EStG) — fully deductible immediately
- Purchase-related expenses (§ 6 Abs. 1 No. 1a EStG) — depreciated over time if more than 15 % of the purchase price within 3 years
- Construction costs — standard depreciation → 2 % or 3 %
- Movable assets (§ 7 EStG) — own useful life, often 5–10 years
Concretely, this means: If you replace only one heating thermostat with a smart model, it is considered maintenance cost. However, if you install a fully networked KNX system with new wiring as part of a renovation within the first three years after purchase, you will regularly fall below the 15% threshold of the acquisition-related costs — and must amortize the remaining useful life. As described in the guide Real Estate as an Investment, you should consciously schedule the renovation phase for the fourth year after purchase to ensure the full tax effect.
Funding: How banks assess smart real estate
Since the EU Taxonomy and the tightening of the KfW funding framework in 2023/2024, efficiency criteria are directly included in the lending decision. Anyone presenting a property with energy efficiency class A or B — which is realistically achievable with intelligent building technology — receives interest rate reductions of 0.10–0.30 percentage points compared to class D properties at many banks.
With a loan of 1.5 million € and a repayment period of 20 years, the interest savings alone amount to 30,000–90,000 €. In addition, KfW repayment grants of up to 45,000 € per residential unit (Program 261/262) apply. The aspect of mortgage repayment planning thus gains an additional dimension. Anyone who is setting up real estate financing anyway should integrate the smart home portion from the beginning into the collateral documents.
Capital gains tax & exit: Smart technology when selling
When selling within the ten-year speculation period (§ 23 EStG), the smart home investments are counted as value-enhancing in the acquisition/production cost block. This reduces the taxable gain on disposal. Example: You have invested 35,000 € in premium technology and sell after eight years with a book profit of 280,000 €. With a personal tax rate of 42%, the allocation reduces your tax burden by around 14,700 €.
Before each exit, it’s worth checking the
Decision aid: Is smart technology worth it for your investment?
The honest answer is: not always. The following heuristic has proven itself in practice and replaces a formal decision tree:
- Location A+ (Munich, Hamburg) — Premium upgrade is almost always worthwhile
- Location B (medium-sized cities) — Comfort level is usually optimal
- Location C (periphery) — only basic smart, otherwise overinvestment
- Holding period < 5 years — only maintenance measures
- Holding period > 10 years — full KNX upgrade economically sensible
- New construction — always plan for smart-ready wiring
For the initial investment in this field, I recommend fully equipping a single property — ideally the pilot project — and measuring the results over two rental cycles. Those investing for the first time will find concrete step-by-step guidance in our guide to buying your first property. Those looking to scale should take the leap to buying an apartment building — there, the smart-building leverage per invested euro is the greatest.
FAQ — Frequently asked questions from investors
How does intelligent building technology affect the market value?
Current market analyses show premiums of 5–12 % compared to similar properties without smart fittings, up to 15 % in premium locations. However, the quality of integration is crucial: an outdated island solution system can even reduce value, as buyers may factor in a potential dismantling. Therefore, invest in open, standardized systems such as KNX, Matter or ZigBee 3.0, which will still be supported in ten years’ time.
Can I pass on Smart-Home costs as a landlord?
Pure investment costs are not passable on to tenants, but ongoing maintenance and service costs of the system according to § 2 BetrKV can be, provided this is explicitly regulated in the rental agreement. Modernizations according to § 559 BGB also allow for a rent increase of 8 % of the costs incurred per year — for a 20,000 € Smart-Home investment this would be 1,600 € annually, distributed across the affected residential units. This must be formally announced and justified.
Which Smart-Home investment is the biggest return driver?
From an investor’s perspective, clearly the combination of individual room heating control, photovoltaics with battery storage, and intelligent wallbox. This combination reduces additional costs by 25–40 %, qualifies for KfW funding, and often moves the energy efficiency class up by two levels. The payback period typically lies between six and nine years at current energy prices — with a remaining useful life of the technology of 15–20 years, this is clearly a positive business.
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