Solar electricity every hour of every day is here and it changes everything

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Ember Report - Solar electricity every hour of every day is here and it changes everything

Methodology

We model the operation and Levelized Cost of Electricity (LCOE) of a solar PV system paired with battery storage at a specific location, using hourly solar irradiance data. The simulation runs over a full year and is repeated across multiple capacity scenarios to assess system performance and economics.

The system is assumed to be DC-coupled, with no grid imports and a target export to the grid of 1 GW. The model tracks the battery’s state of charge hourly. Surplus solar generation beyond the 1 GW target charges the battery. After the battery reaches maximum charge, any additional solar generation is curtailed. The battery discharges when solar alone cannot meet the 1 GW target until it reaches the minimum state of charge. Energy losses across the system are captured at each step.

The model outputs total energy delivered to the grid, curtailed solar generation, unmet demand, and calculates the LCOE over a 20-year project lifetime.

Data sources

The model uses hourly solar generation data from the European Commission’s PVGIS tool. Fixed-tilt PV systems are assumed, with location-specific optimisation for slope and orientation. Where SARAH3 irradiance data is unavailable, ERA5 is used.

Technical Constraints

Battery usable capacity: 90% of nameplate.
- State-of-charge limits: minimum 5%, maximum 95%.
Energy losses included:
- PV to Grid: 96.24%
- PV to Battery: 98.2%
- Battery to Grid: 96.24%
- Full round-trip: 94.4%

Financial assumptions

Project lifetime: 20 years.
Discount rate: 7.7%.
Annual operational cost escalation: 2.5%.
Degradation rates:
- Solar PV: 0.5% per year.
- Battery: 2.6% per year.
Capital costs based on latest market estimates (PV, battery, grid connection, inverter, soft costs).
Operating costs benchmarked from industry reports.
LCOE is calculated as total discounted cost divided by total discounted energy supplied to the grid.

For detailed methodology, please refer to pages 38- 45 of the report.

Acknowledgements

Contributors

Rashmi Mishra, Reynaldo Dizon, Richard Black, Neshwin Rodrigues, Beatrice Petrovich, Kingsmill Bond, Hannah Broadbent, Matt Ewen, Wilmar Suarez, Sam Hawkins, Daan Walter, Kavya Sharma.