Guide · 7 min read
Letting sustainably —lower costs, less CO₂
Energy-efficient refurbishment, heat pump, PV system — what's really worth it? We do the maths: which measures reduce your landlord's CO₂ share + costs + rent-loss risk from future refurbishment obligations.
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Why sustainability pays off for landlords
- CO₂ cost share falls (CO₂ cost allocation 10-tier model)
- Energy-efficient letting → higher permitted rent and a better choice of tenants
- KfW funding of up to 70% of the refurbishment costs possible
- Special tax depreciation §7h EStG (9% annually!)
- Increase in value on a later sale
- Avoid future refurbishment obligations (GEG, EU minimum energy efficiency from 2030)
Top 5 measures with the highest ROI
1. Hydraulic balancing (5-15% efficiency)
- Cost: €500-1,500 (often with BEG funding 15-25%)
- Amortisation: 2-4 Jahre
- Mandatory for buildings >1000 m² since 2024
- Very simple, quick to implement
2. Heating modernisation: natural gas → heat pump
- Cost: €25,000-45,000 (BEG funding of up to 70% possible)
- CO₂ reduction: jump of 3-5 levels in the CO₂ cost allocation
- Amortisation: 8-15 Jahre
- Effect: with good values, tier 1-2 instead of 6-8 = landlord's share 0-10% instead of 50-80%
3. Roof insulation + façade insulation
- Cost: €80-150/m² (BEG funding 15-25%)
- Effect: 20-40% reduction in heating costs
- Amortisation: 10-15 Jahre
- Modernisation surcharge: 8% of the invested costs on the annual rent (German Civil Code)
4. PV system for tenant electricity
- Cost: €8,000-25,000 depending on size
- Revenue: the tenant pays for discounted electricity + feed-in tariff
- KfW funding: up to €7,500 + 0% loan
- EEG funding: 8 ct/kWh guaranteed for 20 years
- Amortisation: 10-15 Jahre
5. Smart-home heating control
- Cost: €300-1,500 per flat
- Effect: 8-15% reduction in heating costs
- Tenant benefit: better comfort control
- Plus point: shows the landlord's commitment = higher loyalty
Your utility bill statement in 10 minutes instead of 3 hours
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2026 funding overview
- KfW BEG: up to 70% of the refurbishment costs (combined with heating replacement + insulation)
- BAFA: 25-40% funding for efficient heat generators
- Individual measures: 15-25%, can be stacked
- Energy efficiency adviser (mandatory for BEG): 50-80% funding of the adviser costs
- KfW 58 loan (residential building refurbishment): up to €150,000, 0.1% interest
When does what make economic sense?
- <5 years holding period? → Only small measures (hydraulic balancing, smart heating)
- 5-10 years? → heating system upgrade with BEG funding
- 10+ years? → full renovation with insulation + heat pump
- Selling within <3 years? → Better not to refurbish (the investment won't be recouped)
How Rentprime helps you
Rentprime has a Energy optimisation module(in preparation, Q4 2026): you enter energy consumption + heating type, the system shows the CO₂ cost allocation level and which renovation measure achieves which level reduction. Plus: KfW subsidy calculator, modernisation surcharge calculation (Common law), tax optimisation tips (special depreciation §7h).
Related topics: Understanding CO₂ cost allocation · German heating regulation update · Energy performance certificate obligations