How big a solar battery do I need to store all my home's electricity? Terence Eden shares an analysis of how large a battery would be required to store all the solar electricity generated by his suburban London home, aiming to be completely energy self-sufficient. --- Background Terence has solar panels generating about 3,800 kWh/year, roughly equal to his annual consumption. Solar production peaks during the day (after sunrise to sunset), but electricity usage peaks in the evening. Excess solar power during the day is exported to the grid; at night, electricity is imported. A single summer day example: House used 9.7 kWh, produced 19.6 kWh. Naively, a 9.9 kWh battery would store excess. However, because consumption doesn't align with production, a 13 kWh battery would be needed for that day’s excess. --- Objective Find the maximum size battery needed to store all excess summer solar electricity for use in winter, based on several years of real household energy data. --- Disclaimer Data is from home battery probes measuring solar and grid flow, with approx. 1-2% measurement error. Personal usage patterns and existing 4.8 kWh battery affect figures. Does not include gas heating or hot water, which impact overall energy use. The analysis is mainly academic; current technology doesn't support such large residential battery installations economically or practically. --- Data Analysis and Code Focus is April 1, 2024 to March 31, 2025 — when solar generation exceeds consumption (spring to autumn). The difference between solar production and household consumption is cumulatively summed (in 5-minute intervals). Python code snippet uses Pandas to: Load and combine CSV data. Compute the cumulative difference in watt-hours, converted to kWh. The maximum cumulative deficit indicates peak battery size needed. Result: 1,068 kWh (over 1 Megawatt-hour) battery capacity required to be fully self-sufficient. --- Visualizations Graph of power flow over a typical summer day shows solar generation, household consumption, and grid import/export dynamics. Cumulative graph over the year displays storage requirement peaking around 1 MWh, then declining as solar tapers off. Even with such battery capacity, occasional grid import would still be necessary. --- Discussion: Is this sensible or possible? Sensible? Probably not domestic scale now. Doesn’t consider future energy needs, e.g., electric cars or all-electric heating. Solar panel efficiency improvements may be more economical (adding/replacing panels). Environmental impact of manufacturing/disposing large batteries matters. A rarely-full massive battery is inefficient; sharing resources on the grid with wind/hydro makes more sense. Possible? Grid-scale batteries exist and work efficiently. Cost estimate for 1 MWh home battery today: £100k - £500k (excluding installation, maintenance, permits). Battery costs have dropped 90% in a decade; emerging sodium-ion tech could reduce costs further (~US$10/kWh). If prices drop as expected, a 1 MWh domestic battery could cost ~£8,000. A future with solar self-sufficient homes storing yearly excess energy in big batteries is plausible. --- Social and Further Interaction Readers are encouraged to share thoughts via comments or social media. A comment noted the size estimate was larger than expected and questioned ecological impact. --- Summary To store all solar electricity generated over summer for winter use in a typical UK suburban home, a battery of about 1 MWh capacity is needed. This is currently impractical but might become viable with ongoing battery tech advancements. Domestic solar combined with suitably sized batteries offers promising energy independence potential, but massive batteries per home may not be the optimal or ecological solution. --- ##