> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nomos.energy/llms.txt
> Use this file to discover all available pages before exploring further.

# Savings calculator methodology

> Every value, assumption and source behind the Nomos savings estimate, so you can explain and defend the number your customers see.

The savings calculator estimates what a household saves per year on a Nomos dynamic plan compared to a typical fixed-price tariff. This page lists every figure the calculation rests on, where each one comes from, and how they combine, so you can answer a customer's "where does this number come from?" without guessing.

The customer-facing "Erfahre mehr" disclosure in checkout shows the same figures. The tables below are generated from the calculator's source code, so they always match what the calculator actually computes.

## How the estimate is built

The saving is the sum of five rows in three buckets. Each bucket only credits what the one before it left off, so the rows never double-count.

| Bucket | Row | What it compares |
| - | - | - |
| 1. Better plan conditions | Base fee | The plan's base fee against the market-average supplier base fee |
| 1. Better plan conditions | Energy price | The plan's unoptimized energy price (spot plus margin) against the market-average supplier energy price |
| 2. §14a EnWG grid fee reduction | Module 1 | The flat yearly grid fee deduction for a controllable device |
| 2. §14a EnWG grid fee reduction | Module 3 | The time-variable grid fee against the operator's static grid fee |
| 3. Optimization | Load shifting | Shifting consumption into cheap hours, plus battery arbitrage |

All amounts are gross, including 19 % VAT.

### What is left out on purpose

Grid fees, metering charges, levies and taxes are the same whoever supplies the electricity. They appear on both sides of the comparison and cancel, so Bucket 1 compares supplier components only. Counting them would inflate both bills without changing the difference.

Feed-in revenue is not part of the estimate. For households with PV the result is therefore conservative.

### Bucket 1: better plan conditions

When the customer does not enter their current tariff, the calculator compares against the market benchmark below. The result is marked as an estimate.

When the customer enters their current tariff, the base fee is taken as entered (without grid and metering base fee), and the regional grid fee, levies and taxes are subtracted from their all-in energy price before comparing.

```text theme={null}
base fee row     = comparison base fee - plan base fee
energy price row = (comparison ct/kWh - (spot ct/kWh + plan margin ct/kWh)) x consumption / 100
```

The spot price and plan margin are the ones the plan's own quote is priced on for the customer's postcode.

### Bucket 2: §14a EnWG

A household qualifies with at least one controllable device: an EV wallbox, a heat pump, or a battery above the power threshold listed under [defaults and thresholds](#defaults-and-thresholds).

* **Module 1** is read directly from the plan's quote for the customer's grid operator. It is a fact about their bill, not an estimate.
* **Module 3** compares the operator's static grid fee against a blend of the operator's own low, standard and high window rates, weighted by the window shares listed below. Operators only have to apply time-variable rates in some quarters, so the saving is scaled by the share of the year the schedule is active.

```text theme={null}
module 3 row = (static rate - (low share x low rate + standard share x standard rate + high share x high rate))
               x consumption / 100 x active share of the year
```

A row is zero when the household does not qualify, declines §14a, the plan does not offer the module, or the grid operator publishes no Module 3 schedule. The calculator never substitutes a national average for a missing schedule.

### Bucket 3: optimization

Each part of the household's consumption gets its own reduction on the spot share of the price. An EV can move almost all of its charging into cheap hours, base load hardly any. The household's optimization rate is the consumption-weighted average of those reductions.

```text theme={null}
optimization rate = 1 - (base kWh x (1 - base reduction) + EV kWh x (1 - EV reduction) + heat pump kWh x (1 - heat pump reduction)) / total kWh
load shifting row = spot ct/kWh x optimization rate x consumption / 100 + battery arbitrage
```

The plan margin is not reduced. A battery adds a fixed yearly amount instead of a percentage, because its earnings scale with cycles, not consumption. A battery behind a PV system adds nothing: it serves self-consumption, and charging it from the grid would put the EEG feed-in remuneration at risk.

### Consumption

The customer enters base load (or picks a household size), plus each asset's consumption. EV consumption is distance x consumption per 100 km x home charging share. With PV, every component is scaled down by the self-sufficiency share, so the mix and with it the optimization rate stay the same.

## Values and sources

<Note>
  Partners integrating the API get the same calculation from `POST /plans/{id}
      /savings`, available from API version `2026-09-08.gauss`. Its response carries
  the five rows, the optimization rate and the §14a eligibility described above.
</Note>

Figures as of **2026-08-26**. Every saving the calculator returns is stamped with this version.

### Market benchmark

| Parameter | Value | Source | As of | Rationale shown to customers |
| - | - | - | - | - |
| Market-average supplier base fee | 78 EUR/year (gross) | CHECK24-Stichprobe Jul 2026 (via Rabot „Strompreise 2026“), bereinigt um BNetzA-Monitoringbericht 2025 Tab. 24 (S. 106) und Tab. 38 (S. 169–170) | 2026-07-21 | Durchschnittliche Grundgebühr des Lieferanten am Markt, ohne Netz- und Messstellengebühr. Diese beiden Posten werden unverändert weitergerechnet, ein Vergleich würde also Ersparnis vortäuschen, die es nicht gibt. |
| Market-average supplier energy price | 15.9 ct/kWh (gross) | BDEW-Strompreisanalyse April 2026, Folien 2, 6, 11 | 2026-04-30 | Durchschnittlicher Arbeitspreis des Lieferanten am Markt, ohne Netzentgelte, Messstellengebühr, Umlagen und Steuern. Auf 3.500 kWh/Jahr normiert, die Grundgebühr ist anteilig herausgerechnet. |

The energy price benchmark is normalized to 3,500 kWh per year.

### Optimization

| Parameter | Value | Source | As of | Rationale shown to customers |
| - | - | - | - | - |
| Spot reduction, household base load | 5 % | Neon-Kurzstudie für naturstrom 2025, S. 7 (20–70 €/a ohne Flexgeräte) | 2025-12-31 | Grundlast lässt sich kaum verschieben. Die 5 % entstehen dadurch, dass Verbrauch wie Waschmaschine oder Trockner in günstige Stunden rutscht. Bandbreite der Studien: 3–8 %. |
| Spot reduction, EV charging at home | 65 % | Neon 2025, S. 8 Abb. 3 (−31 % auf die gesamte Laderechnung); FfE 2024 (197–422 € pro E-Auto und Jahr) | 2025-12-31 | Ein E-Auto lädt planbar und über viele Stunden, deshalb landet der Ladevorgang fast vollständig in den günstigsten Stunden. Bandbreite: 60–70 %. |
| Spot reduction, heat pump | 25 % | Neon 2025, S. 9 (124 €/a); Pufferkurve Ali et al. 2014, Tab. 4.I | 2025-12-31 | Eine Wärmepumpe kann nur so weit vorheizen, wie der Pufferspeicher und die Gebäudeträgheit es zulassen. Bandbreite: 20–30 %, mit größerem Puffer mehr. |
| Battery arbitrage without PV, up to 7.5 kWh | 70 EUR/year (gross) | HTW Berlin / Meissner 2025, S. 3 (69 €/a) | 2025-12-31 | Ein Heimspeicher ohne Solaranlage verdient an der Differenz zwischen günstigen und teuren Stunden. Bandbreite der Studien: 0–225 €/Jahr. |
| Battery arbitrage without PV, above 7.5 kWh | 120 EUR/year (gross) | HTW Berlin / Meissner 2025, S. 3, hochgerechnet | 2025-12-31 | Ein größerer Speicher verdient mehr, aber nicht proportional: die zusätzliche Kapazität lohnt nur an Tagen mit besonders großer Preisspanne. |
| Battery arbitrage with PV | 0 EUR/year (gross) | Lorenz et al. 2026 | 2026-01-31 | Ein Speicher hinter einer Solaranlage puffert den eigenen Solarstrom. Ihn zusätzlich aus dem Netz zu laden würde die EEG-Einspeisevergütung gefährden, deshalb rechnen wir hier keine Ersparnis an. |

### Optimization rate by household

The optimization rate is the consumption-weighted average of the spot reductions above, computed with the default consumption figures below. Real households get the rate their own mix earns.

| Household | Base load | EV charging | Heat pump | Optimization rate |
| - | - | - | - | - |
| Household only | 2,800 kWh | 0 kWh | 0 kWh | 5 % |
| Household and heat pump | 2,800 kWh | 0 kWh | 5,800 kWh | 18 % |
| Household and EV | 2,800 kWh | 1,477 kWh | 0 kWh | 26 % |
| Household, EV and heat pump | 2,800 kWh | 1,477 kWh | 5,800 kWh | 25 % |

### Time-variable grid fees (Module 3)

| Window | Assumed share of consumption |
| - | - |
| Low | 50 % |
| Standard | 40 % |
| High | 10 % |

The calculator prices Module 3 on the grid operator's published schedule. The fallback rates below are national averages, used only where no postcode is known yet. They never replace a missing operator schedule.

| Parameter | Value | Source | As of | Rationale shown to customers |
| - | - | - | - | - |
| Fallback grid fee, low window | 2.6 ct/kWh (gross) | Branchenportal Variable Netzentgelte (via Vattenfall); bestätigt durch Meissner 2025, S. 32 (Median 2,5 über 14 Netzbetreiber) | 2026-01-31 | Durchschnittliches Netzentgelt im Niedrigtarif-Fenster über alle 866 deutschen Netzbetreiber. |
| Fallback grid fee, standard window | 8.7 ct/kWh (gross) | Branchenportal Variable Netzentgelte (via Vattenfall); bestätigt durch Meissner 2025, S. 32 (Median 8,5) | 2026-01-31 | Durchschnittliches Netzentgelt im Standardtarif-Fenster. Ohne Modul 3 zahlt man diesen Satz rund um die Uhr. |
| Fallback grid fee, high window | 12.5 ct/kWh (gross) | Branchenportal Variable Netzentgelte (via Vattenfall); bestätigt durch Meissner 2025, S. 32 (Median 12,8) | 2026-01-31 | Durchschnittliches Netzentgelt im Hochtarif-Fenster. |

### Consumption and solar

| Parameter | Value | Source | As of | Rationale shown to customers |
| - | - | - | - | - |
| EV consumption | 21 kWh/100 km | Neon 2025, Tab. 1; Gegenprobe Stute & Klobasa 2024 (0,15–0,20 kWh/km) | 2025-12-31 | Durchschnittlicher Verbrauch eines Elektroautos inklusive Ladeverlusten. |
| Self-sufficiency, PV without battery | 30 % | Fraunhofer ISE (typisch 25–40 %) | 2026-01-31 | Ohne Speicher deckt eine Solaranlage rund 30 % des Verbrauchs, weil der Strom dann anfällt, wenn niemand zu Hause ist. |
| Self-sufficiency, PV and battery with heat pump | 50 % | Worms 2026, S. 5 | 2026-01-31 | Mit Speicher und Wärmepumpe steigt der Eigenverbrauch, weil die Wärmepumpe den Solarstrom tagsüber abnimmt. |
| Self-sufficiency, PV and battery without heat pump | 75 % | Worms 2026, S. 5 | 2026-01-31 | Ein Speicher in einem Haushalt ohne Wärmepumpe deckt einen großen Teil des Verbrauchs, weil der Verbrauch insgesamt klein ist. |
| Cost of self-consumed solar power | 6 ct/kWh (gross) | HTW Berlin Speicherrechner; noch gegen weitere Quellen zu prüfen | 2026-01-31 | Solarstrom vom eigenen Dach ist nicht kostenlos: über die Lebensdauer der Anlage kostet er rund 6 ct/kWh. |

### Defaults and thresholds

| Parameter | Default |
| - | - |
| Base load, 1 person | 1,800 kWh/year |
| Base load, 2 people | 2,800 kWh/year |
| Base load, 3 people | 3,600 kWh/year |
| Base load, 4 people | 4,200 kWh/year |
| EV distance | 10,500 km/year |
| EV home charging share | 67 % |
| Heat pump consumption | 5,800 kWh/year |
| PV peak power | 8 kWp |
| Battery | 10 kWh, 5 kW |
| Minimum battery power for §14a EnWG | more than 4.2 kW |

## Literature

The values above are derived from these publications. Ranges in the rationale column are the spread across studies. The value column is the figure the calculator uses.

| Short name | Publication |
| - | - |
| Neon 2025 | [Neon Energiesysteme, Kurzstudie für naturstrom: Dynamischer Stromtarif (Oct 2025)](https://neon.energy/Neon-Dynamischer-Stromtarif.pdf) |
| FfE 2024 | [FfE: Is charging electric vehicles with variable tariffs worthwhile?](https://www.ffe.de/en/publications/is-charging-electric-vehicles-with-variable-tariffs-worthwile/) |
| Ali et al. 2014 | [Ali et al., via Aalto University dissertation, Table 4.I](https://aaltodoc.aalto.fi/server/api/core/bitstreams/21de074f-78d1-48c0-83ae-2aed24f23570/content) |
| Stute & Klobasa 2024 | [Stute and Klobasa, Energy Policy 189 (2024)](https://www.sciencedirect.com/science/article/pii/S030142152400082X) |
| Meissner 2025 | [Meissner, HTW Berlin: Einfluss dynamischer Stromtarife (2025)](https://solar.htw-berlin.de/publikationen/einfluss-dynamischer-stromtarife/) |
| Lorenz et al. 2026 | [Lorenz et al., Energy Policy 209 (2026)](https://www.sciencedirect.com/science/article/pii/S0301421525004598) |
| Worms 2026 | [BNS Fachstudie: Effizienz von Batteriespeichersystemen mit dynamischen Stromtarifen (2026)](https://www.worms.de/neu-de-wAssets/docs/zukunft-gestalten/klima-umwelt/Energie/BuergerSolarBeratung/_BNS_3_Studie_A_Effizienz_von_Batteriespeichersystemen_mit_dynamischen_Stromtarifen-Fachstudie_2026_mit_Querverweisen-final.pdf) |
| HTW Stromspeicher-Inspektion 2026 | [HTW Berlin: Stromspeicher-Inspektion 2026](https://solar.htw-berlin.de/studien/stromspeicher-inspektion-2026/) |
| BDEW-Strompreisanalyse | BDEW Strompreisanalyse, April 2026 |
| BNetzA-Monitoringbericht | Bundesnetzagentur and Bundeskartellamt, Monitoringbericht 2025 |


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