Solar Self-Consumption Calculator
Work out what share of your solar production you actually use on-site (self-consumption) versus export, and how much of your home use it covers (self-sufficiency).
How it works
On-site = direct use + battery-stored (capped at production and at usage) · Self-consumption% = on-site ÷ production · Self-sufficiency% = on-site ÷ usage
Self-consumption is the share of your solar output you use yourself rather than sending to the grid, while self-sufficiency is the share of your household demand your solar meets. They answer different questions: high self-consumption means little wasted export, high self-sufficiency means little imported power. A battery lifts both by shifting midday surplus into the evening, but neither can exceed the smaller of production and usage on a given day.
Worked example
You produce 30 kWh and use 25 kWh a day. 12 kWh runs the house directly and 6 kWh charges the battery for the evening, so 18 kWh is used on-site. Self-consumption is 18 ÷ 30 = 60%; self-sufficiency is 18 ÷ 25 = 72%. The remaining 12 kWh is exported and 7 kWh still comes from the grid.
Frequently asked questions
Why does self-consumption matter?
In many places exported solar is credited far below the retail price you pay to import, so every kWh you use yourself is worth more than one you export. Raising self-consumption — by shifting loads to daytime or adding a battery — improves the economics of a solar system.
What is a typical self-consumption rate?
A solar-only home often lands around 30–40% because production peaks midday when nobody is home. Adding a battery and timing big loads (EV, dishwasher, laundry) for daylight commonly pushes it to 60–80%.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.