Solar calculator: compare generation, storage and savings
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Compare 81 saved hourly reference scenarios for the same 5 kWp installation. Choose a city, assumed demand pattern and battery capacity, then enter your own prices. Results show energy, payment differences and simple payback under the stated assumptions. This is not a calculation for a particular roof or a forecast of your bill.
Choose the scenario to compare
All variants use modelled 2023 weather, a south-facing array, 35° tilt and 14% input system losses. Household profiles are constructed assumptions, not measured Slovak households. Choosing a city selects a reference location, not your home's position.
Reference scenario results
Bratislava · 6,000 kWh · even demand profile · no battery.
Default model prices are shown. Enter an investment amount to calculate payback.
| Flow | Energy |
|---|---|
| Panel generation | 5,989 kWh |
| Household consumption | 6,000 kWh |
| Used directly from panels | 2,140 kWh |
| Battery delivery to appliances | 0 kWh |
| Grid imports | 3,860 kWh |
| Surplus exported to the grid | 3,850 kWh |
| Battery conversion losses | 0 kWh |
| Energy remaining in the battery at year end | 0 kWh |
Household demand covered by panels and their battery: 35.7 %. This is a share of household energy use, not a percentage financial saving. Losses are not useful energy delivered.
| Item | Per modelled year |
|---|---|
| Variable electricity purchases without panels | €1,080.00 |
| Variable electricity purchases with panels | €694.84 |
| Value of avoided imports | €385.16 |
| Export value under your assumptions | €153.98 |
| Entered additional fees and operating costs | €0.00 |
| Annual benefit after entered costs | €539.14 |
| Investment after selected support | Not entered |
| Simple payback before support | Enter investment |
| Simple payback after support | Enter investment |
No battery is included. Add one to compare the same model with storage.
Fixed charges common to both cases remain and are not counted as savings. The tool assumes the same variable import price in both cases. If the entire tariff changes on installation, compare the actual bills; here you can include only additional monthly costs. Virtual batteries, quarter-hour electricity sharing and charges for exceeding export capacity are not modelled.
Scenario assumptions and limits
Data version: PVGIS-2023 / hourly model dated 21 October 2026. Generation uses the PVGIS hourly model. It uses reference positions for three cities and a ventilated-module model. It is not a roof survey and does not assess nearby chimney or tree shadows for your home.
Demand profiles have the selected annual total, but their hourly pattern is assumed. The model battery charges and discharges at up to 3 kW with 95% efficiency in each direction. It starts empty, does not charge from the grid and holds no outage reserve. Energy remaining at year end is not counted as consumed.
The model excludes standby consumption, ageing, temperature and BMS limits, differences in inverter clipping and backup-circuit design. Replacement, financing and discounting are not calculated. Annual operating costs include only what you enter.
Simple payback is investment divided by a positive annual benefit. A non-positive benefit gives no positive simple payback. This is neither a guarantee nor a detailed cash-flow calculation. Assumptions and unsuitable cases are explained in the guide to solar payback.
What you need for your own home
- Location and each roof surface, array power, orientation, tilt and a shading assessment.
- Actual demand timing, rather than only an annual total.
- Exact battery, power limits, reserve and equipment consumption.
- Applicable import prices, commercial surplus settlement and all fees.
- A complete quotation and verified support if you want to include it.
The tool does not assess grant eligibility or distribution approval. For an actual offer, use the quote-comparison checklist. Changing prices and assumptions changes the result, but does not turn a reference profile into measurements of your home.
Frequently asked questions
Why can I not enter any installation size?
The tool compares saved chronological scenarios for 5 kWp. It does not scale them to another size in a way that pretends to be a new design and battery calculation.
Are the prefilled prices a current tariff?
No. They are transparent model assumptions. Replace them with your own relevant prices and fees.
Will the calculator select an outage-backup battery?
No. The model follows solar energy shifting without a backup reserve. Backup needs its own wiring and power design.
Does zero support mean I am ineligible?
No. Support is not assessed. It starts at zero until you enter a confirmed amount or an explicit scenario.