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How do we calculate your scenarios?

Simple explanation of our calculation methods

Transparency First

We calculate your energy costs for each scenario based on your annual production and consumption. Below we explain step by step how each scenario works.

Our Assumptions

Energy Prices (2026-2027)

  • • Chosen import scenarios: fixed €0.30/kWh, variable €0.25/kWh including VAT; user-overridable, not market averages
  • • Feed-in now: €0.10/kWh (with net metering you get the import price back)
  • • Chosen post-2027 net export: €0.01/kWh = €0.05 gross − €0.04 fee (fixed/variable); raw wholesale excluding VAT (dynamic, no generic bonus)
  • • Net annual fixed amount: €478.042 Liander 2026 network reference + €100 supplier assumption − €519.80 × 1.21 residential tax credit = −€50.916. 2026 amounts carried into 2027, not finalized 2027 tariffs.

How We Calculate

We calculate every hour of the year (8,760 hours):

  • • Your consumption per hour (NEDU profile or evenly distributed)
  • • Your production per hour (KNMI solar data + your panels)
  • • Per hour: production > consumption = export, consumption > production = import

Now: With net metering

What you export up to your consumption is credited at import price (€0.30/kWh). Extra export receives €0.10/kWh.

The flat-rate formula below applies to fixed and variable contracts. For a dynamic contract, imports and exports are valued hourly and the current model annually offsets energy tax on min(imports, exports). Supplier markups are not netted. This remains a generic model; check your supplier terms. The impact and battery saving compare the same selected contract.

Calculation

Net consumption = Import - min(Export, Import)
Cost = Net consumption × €0.30 + Fixed costs
Extra export = max(0, Export - Import) × €0.10 (bonus)

Example

Suppose:

  • Consumption: 3,000 kWh/year
  • Production: 3,839 kWh/year (illustrative)
  • Import: 762 kWh, Export: 1,601 kWh

Calculation:

  • Net metering: 762 kWh import offset by 762 kWh export = €0
  • Extra export: (1,601 - 762) × €0.10 = €84 bonus
  • Net fixed model amount: −€50.916
  • Illustrative total: −€50.916 − €83.90 = −€134.82/year

After 2027: Fixed contract (no net metering)

Without net metering, our chosen fixed scenario uses €0.30/kWh import and €0.01/kWh net export. Actual contracts may differ; this is not necessarily the worst or best contract.

Calculation

Import cost = Import kWh × €0.30
Export credit = Export kWh × €0.01 (chosen net scenario)
Total = Import cost − Export credit − €50.916 net fixed amount

Why so little for export?

Our scenario subtracts a chosen €0.04/kWh export fee from €0.05/kWh gross compensation. These are modeling assumptions, not market-majority rates or guarantees.

After 2027: Dynamic contract

Dynamic prices vary hourly and may be negative. Import adds VAT, energy tax and a chosen supplier markup; export uses raw wholesale excluding VAT without a generic bonus. Whether this is cheaper depends on prices and your household.

Calculation

Hourly import = kWh × (wholesale ex VAT × 1.21 + 2026 tax €0.09161 × 1.21 + chosen €0.02/kWh markup incl VAT)
Hourly export = kWh × raw wholesale excluding VAT (no generic bonus)
Total = Σ Import − Σ Export − €50.916 net fixed amount (2026 reference carried forward)

How do dynamic prices work?

  • • Results identify the historical price reference year and whether prices are observed, synthetic or estimated; they are not a 2027 forecast
  • • Import: wholesale ex VAT × 1.21 + €0.09161 × 1.21 energy tax + €0.02/kWh chosen markup incl VAT; 2026 tax carried into 2027, not finalized 2027 tax
  • • Export: raw wholesale excluding VAT, without a generic bonus; actual supplier terms differ
  • • Export prices depend on the hours of export and may be negative; no guaranteed average

Extra savings through smart consumption

By running dishwasher, washing machine and EV during cheap hours you save extra:

  • • Standard household: 15% of consumption is flexible. Savings: €20-50/year extra.
  • • With EV or heat pump: 35% of consumption is flexible. Savings: €50-150/year extra.

Fixed contract + battery

With a battery, you increase self-consumption from ~30% to 60-80%. You import less and only export when the battery is full.

How the battery works

  1. Daytime: excess solar charges the battery
  2. Battery full or power-limited? Remaining surplus goes to the grid (chosen €0.01/kWh net)
  3. Evening: battery powers your home
  4. Battery empty? Then you import from grid

Calculation

Import × €0.30 − Export × €0.01 − €50.916 net fixed amount
Due to higher self-consumption, import is lower
Savings = avoided import cost − forgone export revenue, with battery losses included

Battery assumptions

  • • Example capacity: 10 kWh; 85% usable assumed. Charge and discharge each limited to 0.8 kW, independent of capacity; one approximate power-limited setup, not multiple units
  • • Chosen AC round-trip efficiency: 80% (20% loss); €350/kWh including VAT; 2.5% annual degradation assumed
  • • Self-consumption is simulated, not guaranteed; the 15-year NPV analysis horizon is not a warranty or lifespan promise

Self-consumption calculation

Self-consumption = how much of your solar energy you use yourself. We simulate every hour of the year.

Self-consumption % = Self-used / Total production × 100

The simulation

  1. Each hour: production > consumption? Charge battery
  2. Battery full? Export to grid
  3. Consumption > production? Discharge battery
  4. Battery empty? Import from grid

We assume 20% loss per complete charge/discharge cycle (80% round-trip efficiency)

Example

Illustrative energy balance, not a simulated prediction for your household or the 0.8 kW setup:

  • Production: 5,000 kWh/year
  • Consumption: 4,600 kWh/year
Without battery:
  • • Self-consumption: 2,450 kWh (49%)
  • • Export: 2,550 kWh
  • • Import: 2,150 kWh

Cost: 2,150 × €0.30 − 2,550 × €0.01 − €50.916 = €568.58/year

With 10 kWh battery:
  • • Self-consumption: 3,500 kWh (70%)
  • • Export: 1,237.5 kWh; battery loss: 262.5 kWh (80% round-trip assumption)
  • • Import: 1,100 kWh

Cost: 1,100 × €0.30 − 1,237.5 × €0.01 − €50.916 = €266.71/year

Why does a battery help?

Stored solar energy can reduce imports, but charging forgoes export revenue and incurs losses. Actual savings depend on your contract, usable capacity and charging/discharging power.

Savings: €313/year

(€1,089 - €776 = €313 per year)

Dynamic contract + battery

Combines market prices with smart battery control. The battery charges during cheap hours and discharges during expensive hours.

Smart charging strategy

  1. First: charge from free solar energy
  2. Also: charge from grid at low prices
  3. Discharge during peak prices

Calculation

Σ hourly import cost − Σ hourly wholesale export revenue − €50.916 net fixed amount
Export is less (battery stores more)
Extra savings from price arbitrage (buy low, use when high)

Price arbitrage explained

With a dynamic contract, the battery can 'buy low, sell high'. This means:

  • 1. Charge when prices are low (often at night or solar peak hours)
  • 2. Discharge when prices are high (typically 17:00-21:00)
  • 3. With 80% round-trip efficiency, avoided import value must exceed charging cost divided by 0.80, plus other costs. There is no universal profitable price spread.

Note: the average export price with 'dynamic + battery' may be slightly lower than with 'dynamic only'. This is because the battery stores energy during the highest prices. Export only occurs when the battery is full, usually during the lowest price moments.

Our Data Sources

ENTSO-E: Real hourly market prices (European energy exchange) transparency.entsoe.eu
KNMI: Hourly solar irradiance per region knmi.nl
NEDU: Standard consumption profiles for Dutch households nedu.nl

Questions? Check our FAQ or contact us.

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Related information

Net Metering Explained
Everything about the end of net metering and what it means for you
FAQ
Common questions about solar panels and net metering after 2027