Short answer
The solar payback period is found by dividing the total investment by the annual net benefit. In Antalya, 1 kWp produces about 1,656 kWh a year (PVGIS); the size of the benefit depends on how much of the output you use at home, the unit price of electricity and the low price paid for surplus. Calculate the period with your own quote and bill data.
Key takeaways
- Simple payback period = investment ÷ annual net benefit; the annual benefit consists of the cost avoided through self-consumption, surplus income and running costs.
- In central Antalya, 1 kWp produces about 1,656 kWh a year (PVGIS 5.3, 14% system loss); this is the production input of the calculation.
- Surplus earns only the active energy unit price, which is lower than the total unit charge on the bill. The higher your self-consumption ratio, the shorter the period (interpretation).
- Panel performance declines by about 0.4% a year (TommaTech datasheet), while tariff increases can raise the benefit. Assess both together with a sensitivity analysis.
- The payback period is not a guarantee; the result changes as tariffs, exchange rates and consumption habits change.
The solar payback period is the ratio that shows how many years it takes for your investment to pay for itself through the net benefit it provides each year. In its simplest form the formula is: divide the investment amount by the annual net benefit. The difficulty lies in calculating the "annual net benefit" correctly, because electricity consumed at home and surplus electricity fed to the grid are valued at different prices. In this article we offer a calculation template that works with Antalya data and that you can adapt to your own quote. We do not promise an exact period, because the result depends on the tariff, the exchange rate and your consumption habits.
The solar payback period formula
The following equation is used for the simple payback period:
- Annual production (E): System power (kWp) x 1,656 kWh/kWp. This is the annual specific yield that PVGIS 5.3 gives for central Antalya, for a south-facing system at the optimum tilt (33°) with 14% system losses.
- Self-consumption ratio (s): How much of the energy you produce you use yourself at the same time (between 0 and 1).
- Avoided unit price (Pt): The amount you avoid paying for every kWh you do not buy from the grid; it includes all components on the bill.
- Surplus unit price (Ps): The amount paid for the surplus energy you feed to the grid.
- Annual expenses (G): Recurring items such as maintenance, cleaning, insurance and monitoring.
Annual net benefit = E x [s x Pt + (1 - s) x Ps] - G. Payback period = investment ÷ annual net benefit. You take the investment amount from your quote and the tariff from your bill; in this article we do not invent figures.
For example, for a 5 kWp system E = 5 x 1,656 = 8,280 kWh. If you consume 70% of this output yourself, 5,796 kWh is valued at Pt and the remaining 2,484 kWh at Ps. Once you fill in Pt and Ps with your own tariff information, the annual benefit emerges. It is important to do the calculation for the whole year, because in Antalya 1 kWp produces 168 kWh in July but only 99 kWh in December, and your consumption profile also varies by month.
The two separate prices behind the annual benefit
The most common mistake in a solar payback period calculation is to multiply every kWh produced by the total unit price on the bill. Under the official rules this is not correct. Energy you avoid buying by consuming it at home is worth every component on your bill (energy charge, distribution charge, taxes and levies). Surplus fed to the grid, however, is valued under EPDK's (Turkey's Energy Market Regulatory Authority) net metering procedure of 5 May 2026 at the single-rate active electrical energy unit price of the relevant tariff, which is lower than the total unit charge.
Because of this difference, the higher your self-consumption ratio, the shorter the period. This is an interpretation; the rule it rests on is that only the active energy unit price applies to surplus. For residential subscriptions net metering (mahsuplaşma) is done monthly and there is no sales limit. For non-residential installations, from 1 May 2026 (for those who received a connection approval letter (çağrı mektubu) after 2019), production and consumption are netted hourly. In other words, a business that works intensively during the day naturally has a higher self-consumption ratio.
As a current price reference, EPDK raised retail sales prices from 4 April 2026: the residential increase was 25%, the industrial increase 5.8% and the agricultural activity increase 24.8%. We could not verify an official tariff change for July or October 2026; when you calculate, take the value valid on that day from the EPDK table and note its date.
The production input for Antalya
Using PVGIS rather than guessing production data makes the calculation sturdier. The values given are 1,656 kWh/kWp for central Antalya, 1,649 for Manavgat, 1,615 for Alanya, 1,664 for Kaş, 1,655 for Korkuteli and 1,719 for Elmalı. The difference between districts is limited; the real difference comes from roof orientation, tilt and shading. For example, on an east- or west-facing roof production is lower than on an optimal south-facing roof, and this directly lengthens the payback period.
Calculation template: where do you get the inputs?
| Input | Source | Note |
|---|---|---|
| Investment amount | Written quote | Check whether VAT is included or excluded |
| Annual production | System kWp x PVGIS value | Adjust for real roof orientation and shading |
| Avoided unit price | Latest bill, all components | Date any tariff changes |
| Surplus price | Single-rate active energy unit price in the tariff table | Lower than the total unit charge |
| Self-consumption ratio | Daytime consumption profile, meter data | Lower in a home, can be higher in a business working by day |
| Annual expenses | Maintenance contract, insurance quote | Do not assume zero |
A hypothetical example: how the period changes
The example below is purely for template purposes and contains no real prices. We express the investment in "Investment Unit Value" (IUV) terms: the investment divided by the avoided electricity unit price. So IUV = 5,000 for 1 kWp means that the cost of 1 kWp equals the price of 5,000 kWh of electricity. At 100% self-consumption, the payback period is IUV ÷ 1,656.
| IUV (kWh equivalent / kWp) | Simple payback period (100% self-consumption) |
|---|---|
| 4,000 | about 2.4 years |
| 5,000 | about 3.0 years |
| 6,000 | about 3.6 years |
| 8,000 | about 4.8 years |
Now let us look at the effect of the self-consumption ratio. Hypothetically, assume the surplus price is half the avoided price (Ps = 0.5 x Pt) and IUV is 5,000. This ratio is not real; it is only to show sensitivity.
| Self-consumption ratio | Benefit coefficient | Simple payback period |
|---|---|---|
| 100% | 1.00 | about 3.0 years |
| 80% | 0.90 | about 3.4 years |
| 60% | 0.80 | about 3.8 years |
| 40% | 0.70 | about 4.3 years |
The table shows that self-consumption is one of the most sensitive inputs of the calculation. Shifting the washing machine, dishwasher and air-conditioning schedule to the daytime, or installing a system with a battery, can therefore change the period. One point to note about batteries is that no payment is made for energy fed from the battery to the grid; a battery makes sense only to increase self-consumption. For this topic, see our article on solar systems with batteries.
Degradation and tariff increases: two opposing effects
Panels lose some power over time. According to the TommaTech TT605-144TN10 datasheet, the linear performance warranty starts at 99% in year 1 and falls to 87.4% in year 30; that means a decline of about 0.4% a year. In NREL's 2012 literature review, the median degradation for field modules was found to be 0.5% a year. These reduce annual production very slowly; over the first five years the effect does not exceed a few percent.
On the other hand, if the electricity tariff rises, the avoided cost also rises and the payback period shortens. What the tariff will be in future cannot be known, so it is sensible to run three scenarios: optimistic, base and pessimistic. For panel lifetime and warranty details, see our article on solar panel lifespan.
How does the calculation differ for commercial and agricultural installations?
In businesses, daytime consumption is high, so the self-consumption ratio is naturally higher and the calculation is done under hourly netting. The difference between the unit price in the industrial tariff and the residential tariff also shapes the result; the period for the same kWp can therefore come out differently for a home and a business. In agricultural irrigation, if the pump runs only in season, the distribution of consumption through the year becomes decisive for the calculation. For the business scale, you can find feasibility steps in our article on rooftop solar investment for businesses.
Common calculation mistakes
- Multiplying all output by the total unit price: Surplus is valued at a lower price.
- Forgetting maintenance and inverter replacement: The standard warranty on TommaTech inverters is 5 years; a replacement allowance should be considered in a long-term calculation.
- Overestimating production: Shading, dirt and orientation losses can push it below the PVGIS value.
- Deciding on a single scenario: Tariffs, exchange rates and consumption are variable.
- Not following regulatory changes: Rules such as hourly netting affect the result; verify the current position with the distribution company.
For a quick preliminary calculation with your own figures, you can use the solar energy calculation tool on our site.
How many kW do you need for your bill?Use the solar calculator to see system size, number of panels and annual production straight away.Conclusion
The solar payback period is calculated from the quote amount, PVGIS-based production, the self-consumption ratio and two separate electricity prices. Read the result not as a single number but as a range of scenarios. In a free survey, Solar Nexo reviews your consumption profile and helps you shape your calculation with data specific to your roof; you can use our contact page for details.
Frequently asked questions
How many years does it take for solar panels to pay for themselves?
The period is not fixed; it varies with the investment amount, self-consumption ratio, electricity tariff and your roof's output. The calculation divides the investment by the annual net benefit, which is self-consumption and surplus income minus expenses. Since there is no official average, any promise of a number of years would be misleading; we recommend running a scenario calculation with your own quote and bill data.
Which production value should be used in the payback calculation?
For central Antalya, the PVGIS 5.3 value of 1,656 kWh/kWp a year is a solid starting point; it assumes optimum tilt, south orientation and 14% system loss. If your roof faces east or west, or there is shading, you should lower the value. At the survey, it is right to ask for a production estimate specific to your roof and to ask which loss assumption it is based on.
Is surplus electricity fed to the grid paid at the bill price?
No. Under EPDK's procedure of 5 May 2026, surplus is valued at the single-rate active electrical energy unit price of the relevant tariff. This is lower than the total unit charge on the bill, which includes distribution charges and taxes. Energy consumed at home is therefore worth more for payback than energy fed to the grid; confirm the current unit price from the EPDK table.
How does the self-consumption ratio affect the payback period?
The higher the self-consumption, the shorter the period, because every kWh consumed at home is valued at the total unit charge while a kWh fed to the grid is valued at a lower price. Increasing daytime consumption, scheduling loads or using a battery can raise the ratio; include the cost of these steps too. The size of the effect depends on your tariff structure and consumption profile, so examining hourly or daily consumption data helps.
Does panel degradation lengthen the payback period?
Its effect is small. In the TommaTech 605 W model the linear warranty falls from 99% in year 1 to 87.4% in year 30, a decline of about 0.4% a year. This loss does not exceed a few percent in the early years. Assessed together with factors that raise the benefit, such as tariff increases, it usually changes the total result only modestly; however, you must account for inverter replacement cost separately.
Does adding a battery shorten the payback period?
Not always. A battery can raise self-consumption but also raises the investment amount. In addition, no payment is made for energy fed from the battery to the grid. It can make sense if your night-time consumption is high or you need to keep running during an outage; its economic effect must be calculated separately in terms of both investment and self-consumption, and measuring your night-time consumption is the first step.
Is the simple payback period the same as the real period?
Usually it is not. The simple calculation leaves out tariff increases, panel degradation, inverter replacement and financing cost. For a more realistic picture, you need to prepare an annual cash-flow table that includes these factors and run three scenarios. If you use financing, you should add the interest cost to the table. The result is still an estimate, not a promise; use the range of scenarios as decision support.
Sources
- PVGIS - European Commission JRC
- EPDK Board Decision 14531, Net Metering Procedures and Principles, Official Gazette 5 May 2026
- Amendment to the Regulation on Unlicensed Electricity Generation in the Electricity Market, Official Gazette 2 April 2026
- EPDK electricity and natural gas tariff, 3 April 2026 (AA)
- TommaTech TT605-144TN10 datasheet
- NREL - Photovoltaic Degradation Rates: An Analytical Review (2012)
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