4 kWp solar system: cost and payback
The calculator starts from a 4 kWp system in a house that uses 4,000 kWh of electricity a year. At PLN 5,600 per kWp you pay about PLN 22,400, save about PLN 2,073 a year and get your money back in about 10.8 years. Change the use, price or relief to calculate your own case.
Example: 4 kWp, the house uses 4,000 kWh a year
Simple payback: about 10.8 years
saves about PLN 2,073 a yearabout PLN 173 a monthcost after relief and grants about PLN 22,400
- Used straight away: 1,290 kWh, 32%
- Exported: 2,710 kWh, 68%
Power you do not buy: about PLN {avoided}. The deposit for exported energy covers about PLN {deposit} of your bills.
Cumulative balance over 25 years
After 25 years: about PLN 22,098
With degradation and upkeep the balance turns positive for good after about 13.7 years.
Electricity price from 11 October 2026, estimate
| Year | Output | Saving | Costs | Balance |
|---|---|---|---|---|
| Year 1 | 4,000 kWh | 2,073 PLN | 0 PLN | −20,327 PLN |
| Year 5 | 3,921 kWh | 2,048 PLN | 0 PLN | −12,097 PLN |
| Year 10 | 3,824 kWh | 2,016 PLN | 0 PLN | −1,953 PLN |
| Year 12 | 3,785 kWh | 2,004 PLN | 5,500 PLN | −3,440 PLN |
| Year 15 | 3,729 kWh | 1,987 PLN | 0 PLN | 2,539 PLN |
| Year 20 | 3,637 kWh | 1,959 PLN | 0 PLN | 12,390 PLN |
| Year 25 | 3,547 kWh | 1,930 PLN | 0 PLN | 22,098 PLN |
Assumptions and formulaElectricity price from 11 October 2026
output = 4 kWp × 1,000 kWh = 4,000 kWh used on site = 1,290 kWh, exported = 2,710 kWh, bought = 2,710 kWh saving = 1,290 kWh × PLN 1.04 + deposit PLN 732 = PLN 2,073 a year payback = PLN 22,400 ÷ PLN 2,073 = 10.8 years
- Yield per kWp
- 1,000 kWh/kWpPVGIS 5.3 (JRC): Warsaw, south roof at 35°, about 1050 kWh per kWp, 1000 to be safe
- Price per kWp
- 5,600 PLN/kWpKB.pl, solar prices 2026: PLN 5200-6300 gross per kWp
- Electricity price
- 1.04 PLN/kWhURE G11 tariffs 2026 (PGE, Tauron, Enea, Energa), average with distribution
- Value of 1 kWh exported
- 0.27 PLN/kWhPSE RCEm for April-July 2026 weighted by PV output, times 1.23
- Part of the bill the deposit covers (G11 energy)
- 0.62 PLN/kWhG11 energy prices of default suppliers, URE Masz Wybór comparison
- Deposit: multiplier and refund of unused money
- × 1.23, refund up to 30%
- House without heat pump
- 32 %KosztyDomu.pl hourly simulation on PVGIS 2020-2023 data, Warsaw, 1000 kWh/kWp
- Panel degradation
- 0.5 %/yrNREL, Photovoltaic Degradation Rates: median 0.5% a year
- Inverter replacement
- 5,500 PLNSystemy-fotowoltaika.pl: 5 kW inverter replacement with fitting PLN 5000-6000
- Thermal modernisation relief
- No relief
An estimate. Self-consumption comes from a simulation of a typical house near Warsaw, with net billing settled over a year. Fixed charges, changes in the law and battery replacement are not included. Compare at least three offers before you buy.
How electricity, gas, pellet and coal prices have changed, month by month. Price history
Ready-made calculations
How to use the calculator
- Enter your yearly electricity use from the last 12 months of bills. If you plan a heat pump or an electric car, add their use.
- Enter the system size and the price from your quote, per kWp or in total. Below the size you will see the upper limit of a sensible size for your use.
- Choose whether the house has a heat pump. The calculator then estimates self-consumption from our hourly simulation. If you know yours, set it on the slider.
- Check the electricity price and the value of exported energy, pick your thermal modernisation relief rate and add a home battery if you want one.
- Click Calculate payback. The result keeps updating as you change inputs, and you can copy a link to it.
Why 4 kWp for 4,000 kWh of use
4 kWp is the upper limit of a sensible size for a house using 4,000 kWh a year: the system produces about 4,000 kWh, as much as the house uses in a year. In our simulation the house uses about 1,290 kWh straight away, 32% of output, and exports about 2,710 kWh.
The saving is about PLN 2,073 a year. Going up to 5 kWp adds about PLN 332 a year for an extra PLN 5,600, so that fifth kWp pays back in about 16.9 years. With the 12% relief the whole 4 kWp system pays back in about 9.5 years.
Frequently asked questions
How much does a 4 kWp solar system cost in 2026?
At the KB.pl price range of PLN 5,200-6,300 gross per kWp, about PLN 20,800-25,200 with fitting and 8% VAT. The calculator uses PLN 5,600 per kWp, which is PLN 22,400. Enter the price from your quote.
How much electricity does a 4 kWp system produce?
About 4,000 kWh a year with a cautious 1,000 kWh per kWp. For a south-facing roof near Warsaw PVGIS gives about 1,050 kWh per kWp, or about 4,200 kWh.
How long does a 4 kWp system take to pay back?
In a house using 4,000 kWh a year, about 10.8 years without relief and about 9.5 years with the 12% relief. With panel degradation and a PLN 5,500 inverter replacement in year 12, the balance turns positive for good after about 13.7 years.