Backup-Mirrors/EPrices
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Update README with fee configuration details (v1.1)

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Clarify configuration for provider fees and VAT rates:
negative price provider fee support added in EPrices v1.1
This commit is contained in:
Amir
2026-04-06 03:27:38 +02:00
committed by GitHub
parent 6f3ba88394
commit 7faaaceed0
1 changed files with 23 additions and 9 deletions
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README.md
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@@ -16,7 +16,8 @@ Assistant automations are required for any core functionality.
## Features
- Fetches **15-minute resolution** spot prices for **today** and **tomorrow**
- Automatically applies your **provider fee** and **VAT rate** to raw €/MWh prices
- Automatically applies your **provider fee** and **VAT rate** to raw €/MWh prices —
with **separate fee configuration for negative spot prices**
- Exposes **96 per-day price points** plus **24-hour averages** as JSON text sensors
for use in HA automations and dashboards
- **NVS persistence** — prices survive device reboots without re-fetching
@@ -28,7 +29,7 @@ Assistant automations are required for any core functionality.
- Supports **any Energy-Charts bidding zone** (SI, DE-LU, AT, FR, HR, HU and more)
- Full **diagnostic sensor suite** — NVS status, fetch attempts, API fetch times,
data loaded times, WiFi signal, human-readable uptime
- Provider fee and VAT rate configurable via `secrets.yaml` — **no code changes needed**
- All fee and VAT settings configurable via `secrets.yaml` — **no code changes needed**
---
@@ -46,7 +47,7 @@ Assistant automations are required for any core functionality.
| `eprices.yaml` | Main ESPHome configuration |
| `eprices_nvs.h` | NVS helper — save/load price arrays to ESP32 flash |
| `secrets.yaml` | Your local secrets (not committed to git) |
| `CHANGELOG.md` | Complete sensor and entity ID reference for v1.0 |
| `CHANGELOG.md` | Complete sensor and entity ID reference |
| `VERSION.md` | Version history and release notes |
| `ENTSO-E-PRICES-MIGRATION.md` | Optional — migration guide from the predecessor project |
@@ -71,6 +72,7 @@ eprices_timezone: "Europe/Ljubljana"
eprices_country_bzn: "SI"
eprices_prov_fee: "0.12"
eprices_vat_rate: "0.22"
eprices_neg_prov_fee: "0.30"
```
**Key descriptions:**
@@ -79,8 +81,9 @@ eprices_vat_rate: "0.22"
|---|---|
| `eprices_timezone` | Your local timezone — must match a valid [IANA tz name](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones) |
| `eprices_country_bzn` | Energy-Charts bidding zone code — see [supported zones](#supported-bidding-zones) |
| `eprices_prov_fee` | Provider fee as a decimal multiplier, e.g. `"0.12"` = 12% |
| `eprices_vat_rate` | VAT rate as a decimal multiplier, e.g. `"0.22"` = 22% |
| `eprices_prov_fee` | Provider fee for **positive** spot prices — decimal multiplier, e.g. `"0.12"` = 12% |
| `eprices_vat_rate` | VAT rate — decimal multiplier, e.g. `"0.22"` = 22% |
| `eprices_neg_prov_fee` | Provider fee kept on **negative** spot prices — decimal multiplier, e.g. `"0.30"` means provider keeps 30%, pays you 70%; use `"0.00"` if provider passes the full negative price to you |
| `eprices_api_encryption_key` | 32-byte base64 key for HA API encryption — generate with `openssl rand -base64 32` |
### 3) Flash to your ESP32
@@ -133,11 +136,22 @@ For the full list see the [Energy-Charts API documentation](https://api.energy-c
### Price calculation
Raw prices from the API are in **€/MWh**. EPrices converts them to **€/kWh**
and applies your provider fee and VAT:
and applies your provider fee and VAT. Positive and negative spot prices use
separate fee multipliers, configurable independently in `secrets.yaml`:
```
price_eur_kwh = (raw_eur_mwh / 1000) × (1 + prov_fee) × (1 + vat_rate)
```
| Market price | Formula |
|---|---|
| Positive (`raw ≥ 0`) | `(raw / 1000) × (1 + prov_fee) × (1 + vat_rate)` |
| Negative (`raw < 0`) | `(raw / 1000) × (1 - neg_prov_fee) × (1 + vat_rate)` |
The switch happens on the **raw API price** before any multiplier is applied.
VAT is applied to both cases, consistent with net billing contracts where VAT
is calculated on the monthly net sum (mathematically equivalent due to VAT
being a linear multiplier).
**Example with `prov_fee = 0.12`, `neg_prov_fee = 0.30`, `vat_rate = 0.22`:**
- Spot price `+100 €/MWh` → `(100/1000) × 1.12 × 1.22` = **0.1366 €/kWh** (you pay)
- Spot price `−50 €/MWh` → `(−50/1000) × 0.70 × 1.22` = **−0.0427 €/kWh** (you receive)
### Negative prices