← U.S. Residential Solar Fundamentals
Self-consumption, import, and export
By the end: Balance generation and household consumption over a period without a battery.
Self-consumption means using generated solar energy in the home as it is produced. Import means taking energy from the grid; export means sending energy to it. Over a day, the home can do both at different times. A daily total hides when generation and demand occurred.
For a simplified home with no storage or other generation, solar generation equals direct self-use plus export. Household consumption equals direct self-use plus import. Use the same period and measurement boundary for every value. These relationships are an energy ledger, not a utility billing rule.
- Daily solar generation: 24 kWh. Direct self-use: 9 kWh. Grid import: 11 kWh.
- Export = 24 − 9 = 15 kWh. Household consumption = 9 + 11 = 20 kWh.
- The day has 4 kWh more export than import, yet the house still needed the grid at some times.
- Adding a battery requires accounting for charge, discharge, losses, and change in stored energy.
Diagram description
In the morning, 1 kW solar and 3 kW household load require 2 kW import. At midday, 5 kW solar and 2 kW load produce 3 kW export. At night, zero solar and 2 kW load require 2 kW import. No battery is modeled.
Quick check
Solar generates 18 kWh, of which 7 kWh is used directly. With no storage, how much is exported?