IRR vs ROI for German Property: Which Return Matters?

When people assess a property in Germany, they often ask one question:

“What is the return?”

The problem is that ROI, cash-on-cash return and IRR answer different questions. Using the wrong one can make a leveraged property look better, or worse, than it really is.

This guide explains the differences and uses a simplified Berlin example to show how the current calculator turns inputs into results. The example is a transparent comparison model, not a rent forecast or investment recommendation.

Quick answer: use IRR for timing and cash flow for liquidity

For a financed German rental property, IRR is useful because it incorporates timing, but it is not a stand-alone verdict. Compare it with cumulative equity ROI, annual cash flow, debt and the assumed resale value.

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1. The three metrics you should not mix up

ROI (return on investment): simple, useful and easy to misuse

The basic formula is:

ROI = Net gain ÷ Investment cost × 100%

Investopedia defines ROI as the profit or loss generated by an investment relative to its cost, usually expressed as a percentage.¹

If you invest €100,000 and receive €120,000 after costs, the net gain is €20,000 and the ROI is 20%. But the formula does not say whether that gain took one year or ten. ROI is useful for a quick total-profit view, but weak as a stand-alone measure for a long holding period.

Cash-on-cash return: the annual cash yield on your equity

Cash-on-cash return asks how much pre-tax annual cash flow your own cash produces:

Cash-on-cash return = Annual pre-tax net cash flow ÷ Initial cash invested × 100%

For a German purchase, initial cash invested should include not only the cash contribution toward the purchase price, but also buyer-side Kaufnebenkosten (ancillary purchase costs) such as Grunderwerbsteuer (real estate transfer tax), notary and land-registry costs, and any buyer-paid agent commission.

This metric helps assess holding-period liquidity. It does not include the future sale or the equity created by mortgage amortisation. The calculator does not display cash-on-cash return as a separate result; you can derive it from the annual net cash flow and the equity entered.

IRR: a return measure that includes timing

IRR, or Internal Rate of Return, is the discount rate that makes the net present value of all cash flows equal to zero.²

A useful property IRR model would normally include acquisition, financing, rent, operating costs, sale proceeds and taxes. The current calculator models ancillary purchase costs, the entered Kaltmiete (net rent excluding operating costs) and Hausgeld (condominium service charge), mortgage payments, the resale value, selling costs and the remaining debt. It does not provide separate inputs for maintenance, vacancy, renovation or tax. Section 7 explains this scope in detail.

IRR therefore answers a question with a time dimension:

“From purchase to sale, what annualised model result follows from the timing and amount of the cash flows on the cash I contributed?”

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2. Why German ancillary purchase costs matter so much

The largest buyer-side tax is real estate transfer tax. Section 11(1) of the federal Real Estate Transfer Tax Act sets a statutory rate of 3.5%, while each Bundesland (federal state) may apply its own rate. The DNotI table dated 28 January 2026 lists rates from 3.5% in Bavaria to 6.5% in Brandenburg, North Rhine-Westphalia, Saarland and Schleswig-Holstein; Berlin is at 6.0%.³

You should also consider:

• Notary and land registry: often around 1.5%–2.0% of the purchase price. Interhyp gives roughly 1.0%–1.5% for notary costs and around 0.5% for land registry fees.⁴
• Agent commission: the amount depends on the contract and transaction. The 3.57% used below is a worked buyer-side assumption, including VAT, not a nationwide default. German law contains specific commission-sharing rules for consumer purchases of apartments and single-family houses.⁵
• Other transaction costs: renovation, due diligence and financing fees vary by deal and are not separate inputs in the calculator.

On a €500,000 purchase, these amounts can change both the upfront cash requirement and the resulting return. Omitting them overstates ROI and IRR.

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3. Reproducible example: a €500,000 Berlin apartment

The following values can be entered directly into the current calculator.

Calculator input mapping

The calculator has no mortgage-term input. For an annuity loan, it calculates the initial payment from the interest rate plus the initial repayment rate. The 25.1-year debt-free result assumes that the 4.0% rate remains unchanged throughout, with no interest-rate reset, follow-on financing or special repayment. It is not a contractual fixed-rate period or loan offer.

The calculator also has no annual property-appreciation input. The 2.0% assumption is used only to derive the absolute resale input of approximately €609,500.

The €25.00/m² rent is an arithmetic input, not a claim that this rent is lawful or achievable for a particular Berlin apartment. Berlin's 2026 rent-control ordinance applies from 1 January 2026 through 31 December 2029, generally limiting a new tenancy to 10% above the local reference rent unless an exception applies. Check the 2026 Berlin rent index, the applicable Mietpreisbremse (rent-control rule) and any statutory exception before using an asking rent.⁶

Purchase-cost calculation

The equity field covers both the purchase price and buyer-side ancillary purchase costs. Entering only the €150,000 cash contribution toward the price would therefore increase the modelled loan to €407,850.

First-year cash flow

The calculator deducts the full entered condominium service charge from net rent. In practice, recoverable operating costs may be covered by the tenant's Betriebskostenvorauszahlung (operating-cost advance), while administration and maintenance costs remain with the owner. A condominium service charge can also include a contribution to the maintenance reserve, but it is not a vacancy reserve. Because the calculator does not separate these components or add the tenant's operating-cost advance, the result is simplified and may be conservative.⁷

As an external check, the first-year cash-on-cash return is:

€2,445 ÷ €207,850 ≈ 1.18%

This percentage is derived manually; it is not a separate calculator output.

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4. What the calculator returns after ten years

The resale and debt calculation is:

The regular year-ten rental cash flow of €2,445 plus the net sale proceeds produces a final-year net cash flow of €331,538.52.

For the mapped inputs above, the investment analysis shows:

These are pre-tax model results. The Equity Multiple compares all positive modelled cash flows with all cash contributions; Total Profit is the sum of the initial outflow and all subsequent net cash flows.

The cumulative equity ROI is defined here as Total Profit divided by initial cash invested: €145,693.52 ÷ €207,850 = 70.10% over the full ten years. It is not an annual return and should not be compared directly with the 5.70% annual IRR. A different ROI denominator, such as total purchase cost, would produce a different percentage, which is why the definition must always be stated.

The calculator's ten-year holding period means 120 model months, not an automatic tax exemption. For a privately held rental property, Einkommensteuergesetz (Income Tax Act, EStG) section 23 can apply when the period between acquisition and sale is no more than ten years. In June 2026, the Federal Fiscal Court again confirmed that the relevant dates are generally those of the binding acquisition and sale contracts, not the transfer of economic ownership. Check the actual notarised contract dates and ownership structure separately.⁸

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5. How to compare sensitivity scenarios correctly

The calculator does not contain an automatic sensitivity matrix. To compare assumptions:

1. Enter the base case and save it as a named scenario.
2. Select that saved scenario before each comparison, change the relevant input manually, and save the changed version under a new name.
3. Compare IRR, Equity Multiple, Total Profit and Annual Net Cash Flow across the saved scenarios.

For resale-price sensitivity, calculate the terminal price externally and enter it in Expected Resale Price. Holding all other mapped inputs constant gives:

This is a manual scenario comparison, not a built-in forecast. The table illustrates how strongly IRR depends on the resale value; it does not predict Berlin property prices.

You can use the same workflow to vary rent per square metre, the condominium service charge, interest, initial repayment, equity, holding period and selling costs. Change one assumption at a time when you want to isolate its effect.

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6. When to use ROI, cash-on-cash return and IRR

Use ROI for a quick total-profit view

ROI is useful when you want to summarise total gain relative to total cost, especially after an investment has ended. It remains incomplete unless the measurement period is also stated.

Use cash-on-cash return for holding-period liquidity

Cash-on-cash return helps you judge whether the property produces cash or requires additional funding during a particular year. It is useful for liquidity planning, but says nothing about sale proceeds or amortisation by itself.

Use IRR to compare cash-flow timing

IRR incorporates cash-flow timing, but it does not account for project scale or risk and can mis-rank projects with different cash-flow patterns. It is also sensitive to leverage and resale assumptions. In an article published by CFA Institute, Ludovic Phalippou explains that interpreting IRR as an achieved return involves assumptions such as reinvesting interim cash flows at the same rate.²

Use IRR together with the Equity Multiple, annual cash-flow profile, remaining debt and conservative sale scenarios. If you have a required return, calculate NPV separately; the calculator does not currently provide it.

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7. Model scope: what is and is not included

The calculator directly models:

• state-specific real estate transfer tax, notary and registry costs, and agent commission;
• available equity, loan amount, interest, repayment and amortisation;
• net rent excluding operating costs as area multiplied by rent per square metre;
• the full entered condominium service charge as a constant monthly cash outflow;
• rent growth, holding period, expected resale price and selling costs;
• the remaining loan deducted from sale proceeds.

The entered interest rate remains constant throughout the modelled amortisation period, and the condominium service charge does not grow over time. The calculator does not model an interest-rate reset or follow-on financing.

It does not provide separate inputs for:

• maintenance, vacancy or renovation;
• recoverable versus non-recoverable components of the condominium service charge or tenant operating-cost advances;
• insurance, financing fees, early-repayment charges or follow-on financing;
• Grundsteuer (annual property tax), income tax, depreciation or tax on a sale.

The output is no more precise than the assumptions entered. Treat the displayed IRR as a pre-tax model result, assess omitted items separately and ask qualified tax, legal and financing advisers to review deal-specific effects before a purchase decision.

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8. How to read the calculator output

In the Investment Analysis panel, the headline outputs appear in this order:

1. Project IRR: the annualised result calculated from synthetic monthly model cash flows spaced at one-twelfth-of-a-year intervals.⁹
2. Equity Multiple: total positive cash flows divided by total cash contributions.
3. Total Profit: the sum of all modelled cash flows, including the initial equity outflow.
4. Annual Net Cash Flow: the year-by-year profile, with sale proceeds included in the final year.

Then open Cash Flow Details to inspect rental income, net sale proceeds, condominium service charge, loan payment, interest, principal, net cash flow, cumulative cash flow and remaining debt. The separate amortisation schedule provides the monthly loan breakdown.

The calculator does not display ROI, cash-on-cash return or an automatic sensitivity analysis. Derive ROI or cash-on-cash separately when needed, and compare sensitivities with saved scenarios as described in section 5.

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FAQ

Is a higher IRR always better?

No. A high IRR can reflect a strong project, but it can also result from higher leverage, low initial equity or an optimistic resale assumption. Compare debt, annual cash flow and the resale value before drawing a conclusion.

Can IRR be positive when monthly cash flow is negative?

Yes. Mortgage amortisation and net sale proceeds can outweigh negative monthly cash flows. Such a project depends more heavily on the eventual sale and requires enough liquidity to fund shortfalls during the holding period.

Which metric is best for a German rental property?

Of these three metrics, IRR is the one that incorporates timing. It is not automatically the best ranking tool: annual cash flow, debt, cumulative ROI and the Equity Multiple remain essential for judging liquidity, scale and risk.

Does the calculator include maintenance, vacancy and tax?

No. Those items do not have separate inputs. The model deducts the entered condominium service charge, which may include a maintenance-reserve contribution but is not a vacancy reserve. Treat the result as pre-tax and assess omitted property-specific costs separately.

Why can Project IRR be unavailable?

IRR requires at least one negative and one positive model cash flow. It can also have more than one mathematically valid result when cash flows change sign repeatedly. The calculator shows IRR as unavailable unless it finds exactly one valid result.

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Conclusion: use IRR with cash flow and explicit assumptions

ROI, cash-on-cash return and IRR answer different questions:

• ROI summarises overall gain relative to a clearly defined cost base and is not annualised automatically.
• Cash-on-cash return measures annual cash flow relative to cash invested.
• IRR annualises all modelled cash flows from purchase to sale.

For a financed German rental property, IRR shows how timing affects the result, but it cannot rank investments or support a purchase decision on its own. Compare it with the explicitly defined cumulative equity ROI, Equity Multiple, annual cash-flow path, remaining debt and resale assumption, and add omitted maintenance, vacancy and tax effects separately.

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Disclaimer: This article is for general education and uses a simplified model. It is not tax, legal, financing or investment advice. German property transactions depend on personal tax circumstances, loan terms, rental contracts, state-specific rules and deal structure. Speak with a tax adviser, notary or independent mortgage adviser before making a purchase decision.

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