Is a solar energy system worthwhile when remodelling a house? An overview of cost-effectiveness and subsidy options
Remodelling a house is often the perfect time to integrate sustainable technologies - first and foremost a solar energy system. But before you decide to install it, the central question arises: Is the investment really worth it? In this article we look at the economic advantages, Funding opportunities and the Long-term savings through photovoltaic systems when remodelling a house.
1. the combination of home remodelling and solar investment - sensible and efficient
A renovation is the ideal time to make major changes to the building technology. The roof may be undergoing renovation or energy efficiency improvements anyway - what could be more obvious than installing solar modules at the same time?
Advantages of a conversion:
- Roof surfaces can be correctly aligned and prepared straight away.
- Cabling and technology (e.g. battery storage, inverters) can be better integrated.
- Synergies with other measures such as insulation, window or heating modernisation ensure additional efficiency gains.
By combining this with construction work that is due to be carried out anyway, the additional installation costs for a solar system - so you save twice as much.
2. cost-benefit analysis: What does a solar system cost - and what does it earn?
The acquisition costs for a photovoltaic system are on average between 1,200 and 1,800 euros per installed kilowatt peak (kWp). A common system with around 8 kWp thus costs approx. 10,000-14,000 euros, depending on the manufacturer, installer and regional conditions.
In addition, there may be:
- Electricity storageapprox. 7.000-10.000 Euro
- Installation and technical customisationdepending on expenditure
On the other hand Annual savings in electricity consumption, as a large proportion of the electricity generated is consumed by the household itself. Depending on household size and consumption 500-1,000 euros per year in electricity costs are eliminated. In addition, surplus electricity is fed into the public grid - there is the so-called Feed-in tariff (currently around 8-9 cent/kWh for systems up to 10 kWp, as of 2025).
Amortisation period:
Depending on subsidies, the proportion of self-consumption and electricity price increases, the Amortisation period of a solar system is usually between 10 and 15 years - with a service life of 25-30 years a worthwhile investment.
3. funding opportunities - clever financing of solar technology
Subsidies are an important factor for economic assessment, especially when it comes to remodelling. In Germany, there are several programmes that either provide direct subsidies or offer particularly favourable loans.
KfW subsidy
The KfW Bank (Kreditanstalt für Wiederaufbau) offers various programmes for energy-efficient construction and renovation. For solar systems in particular, the programme KfW 270 - Renewable energies - Standard relevant. There are low-interest loans for photovoltaics, battery storage and supplementary technology.
BAFA subsidies
The Federal Office of Economics and Export Control (BAFA) currently promotes above all Heat pumps and heating technology - In combination with a solar energy system, however, there can be indirect benefits, for example through intelligently networked control of energy flows.
Regional programmes and tax concessions
Many federal states and local authorities offer additional subsidies or funding programmes. In Berlin, for example, there is the „SolarPLUS“ subsidy programme. In addition, small photovoltaic systems up to 30 kWp have been exempt from VAT and income tax since 2023 - an additional financial advantage.
4. feed-in tariff vs. self-consumption - which is more worthwhile?
In the past, the aim of a solar system was usually to feed in as much electricity as possible - today it is the other way round. The self-generated electricity saves the expensive purchase costs (currently approx. 35-40 cent/kWh) and is thus clearly more valuable than the feed-in tariff (only about 8-9 cent/kWh).
Tip: With a Electricity storage the self-consumption share can be increased to up to 60-80 % This significantly improves economic efficiency, but is associated with additional investment.
5. environmental aspect and property value
In addition to pure economic efficiency, the Environmental concept an average solar system saves several tonnes of energy per year. tonnes of CO₂ an active contribution to climate protection.
In addition, a solar energy system generally also increases the Value of the property. Sustainability is becoming increasingly important, especially for young generations of buyers - a modern energy supply can be a real plus point when selling later on.
Conclusion: When is a solar system worthwhile when remodelling a house?
Integrate a photovoltaic system when remodelling a house, is worthwhile in most cases in the long term - both financially and ecologically. Those who take the opportunity to consider the installation at the planning stage will benefit from lower additional costs and a better overall energy concept.
Recommendation for owners:
- Let us know at an early stage Professional advice, e.g. by energy consultants or specialised solar technology companies.
- Check Regional funding opportunitiesin addition to KfW programmes.
- Calculate self-consumption and amortisation - especially if a storage system is planned.
- Think of the Long-term added valuelower operating costs, greater independence and increased property value.
When remodelling and the energy transition are considered together, investing in a solar energy system is a win-win situation - for your wallet, the environment and the home of tomorrow. You can also find a checklist for your conversion below.
Checklist:
Plan before the conversion
Check roof surfaceInclination, orientation (ideal: south or south-west), shadows cast by trees, neighbouring houses or chimneys?
Clarify staticsIs the roof suitable for the load of solar modules?
Determine energy requirementsAnalyse electricity consumption in recent years - is self-consumption worthwhile?
Include future planning: Are you planning an electric car, heat pump or home office soon?
Profitability & financing
Calculate costsAcquisition costs for PV system + storage system, inverter, mounting systems, if applicable
Obtain offersComparison of several specialised companies in your region
Check subsidies:
- KfW programmes (e.g. KfW 270)
- BAFA subsidies (indirect, e.g. for heating modernisation)
- Regional subsidies (state/federal government/city)
Check tax advantagesVAT exemption, income tax exemption (for <30 kWp)
Technical realisation
Optimise self-consumption: Plan system size according to requirements
Weigh up electricity storage: Is a battery storage system worthwhile in your case?
Planning the connection to the power gridGrid registration with the energy supplier required
Check smart home connection: Energy management system for efficiency gains?
Documentation & legal topics
Inform network operatorsRegistration of the system before commissioning
Market master data registerMandatory entry after commissioning
Check insurancesAdjust building insurance, take out special PV insurance if necessary
Clarify maintenance and service: Organise regular inspection & cleaning
After the remodelling
Set up monitoringMonitoring power generation via app or online portal
Adjust power consumptionUse appliances during the day to maximise self-consumption
Check yieldsAnnual evaluation and readjustment if necessary
Benefit in the long termCheck amortisation regularly, build up reserves for future maintenance
