How big a solar battery do I need to store *all* my home's electricity?

How big a solar battery do I need to store all my home's electricity?

4 hours ago

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A homeowner in suburban London with solar panels generating 3,800kWh annually seeks to determine the battery size needed for complete energy self-sufficiency.
Analysis of a typical summer day shows a peak excess of 13kWh, indicating the need for a larger battery than just the daily excess due to mismatched solar production and household usage patterns.
Using real data from March 2024 to March 2025, the cumulative difference between solar production and household usage suggests a need for approximately 1,068kWh (1MWh) of battery storage to cover annual energy needs.
The exercise highlights impracticalities, including high costs (estimated £100k-£500k), environmental concerns, and inefficiencies in battery usage.
Future possibilities include falling battery prices (e.g., sodium ion batteries at US$10/kWh) and increased solar panel efficiency, potentially making home energy self-sufficiency more feasible.
The discussion acknowledges the ecological imprudence of large domestic batteries and suggests reliance on grid-scale renewable sources as a more sustainable alternative.