Transparent calculations
This page explains how WattBilanz calculates energy flows, financial results, estimated prices and incentives for Switzerland. Every change to formulas or market assumptions receives a new version.
Reproducibility
| Component | Version | Scope |
|---|---|---|
| Core calculation | WB-PV-FREE-1.0.0 | Hourly energy and financial balance |
| Household load | CH-RESIDENTIAL-ETH-EKZ-2023-2024-v1 | Swiss profile based on 196 complete household-years |
| Heat pump | WB-HP-SEASONAL-1.1.0 | Temperature-dependent seasonal distribution |
| Electric car | WB-EV-CHARGING-2.0.0 | Charging profiles tied to driving days |
| Solar prices | CH-PV-NEW-2026-09-v1 | CHF including installation and 8.1% VAT |
| Battery prices | CH-BATTERY-NEW-2026-09-v1 | CHF including installation and 8.1% VAT |
| Local grants | ch-local-2026-09-09-v2 | Versioned regional data with incomplete coverage |
Each result receives a shortened SHA-256 identifier derived from the inputs and model versions. It helps identify the same calculation but is not an electronic signature.
Energy model
For each roof plane, WattBilanz uses hourly PVGIS 5.3 data with SARAH-3, weather years 2014–2023, the natural horizon, crystalline modules and 14% system losses. The ten years are averaged hour by hour and scaled to the entered capacity.
CH-RESIDENTIAL-ETH-EKZ-2023-2024-v1 distributes the entered annual demand exactly. It is based on 110 detached-home meters and 196 complete household-years. Working from home shifts demand in time without changing the annual total.
Its electricity use must already be included in annual consumption. The model separates typical household demand from the heat-pump share and distributes the latter according to temperature, with more energy during the heating season.
Charging energy follows distance, driving days and vehicle consumption. AC charging efficiency is 90%. Solar-surplus, daytime and overnight charging stay within their selected windows; winter demand is not shifted into summer.
| People | Annual consumption | Source |
|---|---|---|
| 1 | 2,270 kWh | SwissEnergy/SFOE |
| 2 | 2,860 kWh | SwissEnergy/SFOE |
| 3 | 3,450 kWh | SwissEnergy/SFOE |
| 4 | 4,050 kWh | SwissEnergy/SFOE |
| 5 | 4,590 kWh | SwissEnergy/SFOE |
| 6 | 5,090 kWh | SwissEnergy/SFOE |
These suggestions exclude electric hot water, heat pumps and electric cars. A household’s own bill always takes priority.
Battery and economics
Usable capacity is 90% of gross capacity. The battery stores solar surplus and supplies a later shortfall with 90% round-trip efficiency. The battery scenario is always compared with the same solar installation without a battery.
The free model keeps prices, tariffs and annual output constant. It compares 0–30 kWh in 1 kWh steps and also calculates the exact capacity entered.
Swiss prices
The figures include installation and Swiss VAT of 8.1%, before grants, and are derived from the SFOE 2025 solar price study. The CHF 2,000 retrofit premium is a provisional integration assumption. An entered quote replaces the estimate for the selected size. The orientation range is 85–115% of the model value.
Switzerland · incentives, export and tax
From 2 kWp, the capacity contribution is calculated progressively. For attached and freestanding systems: CHF 360/kWp up to 30 kWp, CHF 300/kWp from 30 to 100 kWp and CHF 250/kWp above that. Integrated systems use CHF 400, 330 and 250/kWp. A qualifying tilt-angle bonus is added separately.
Only valid, versioned and computable regional rules are deducted. Expired, exhausted, unverified or unclear cumulative programmes are not counted. Coverage is not complete or live.
The statutory model uses the higher of the SFOE reference market price and minimum remuneration. With self-consumption, the minimum is 6 ct/kWh up to 30 kWp, then 180 ÷ capacity in kWp, expressed in ct/kWh, up to 150 kWp. The model stores 3.896 ct/kWh for Q2 2026. A separate guarantee of origin is added only when it is not already bundled.
The separate orientation is the investment after incentives multiplied by the entered marginal tax rate. It changes neither annual savings, payback nor the 20-year result. Actual treatment depends on the canton and personal circumstances.
Model limits
WattBilanz provides financial orientation. A qualified contractor must assess the building, grid connection, shading and actual quotation.
Data and external services
The town or postcode is checked against the official swisstopo directory. A Switzerland-only location search then provides coordinates for PVGIS. No precise street address is requested.
Technical and tariff inputs are sent to the WattBilanz server for calculation. A shared result link contains encoded inputs so the result can be reproduced. Local browser storage is used only after consent.
Sources
Prices dated 8 September 2026 · Incentives and tariffs dated 9 September 2026 or the stated tariff period.