What is self-consumption rate?

Self-consumption rate is the share of your solar generation that is used on-site at the moment it is produced, rather than exported to the grid. It is the hour-by-hour overlap of generation and load divided by total generation, and it determines how much value you capture at retail rates.

Why does the time-of-day shape matter so much?

Solar peaks at midday while many homes peak in the evening, so a large fraction can be exported even when daily totals match. Shifting the load shape toward midday, or storing midday surplus, raises self-consumption without changing the daily energy totals.

How is export volume calculated?

For each hour the tool takes the lesser of generation and load as self-consumed, and any generation above the load in that hour as exported. Summing exported energy across all hours and multiplying by 365 gives the estimated annual grid export in kWh.

How does this inform a battery decision?

A battery captures midday surplus that would otherwise be exported and releases it in the evening, raising self-consumption. The annual export volume shown here is roughly the energy a battery could time-shift, so it bounds the savings from storage versus selling at the export rate.

Is this an exact figure?

No. It uses smooth representative hourly profiles, not your real interval data, and ignores day-to-day and seasonal weather variation. It is a planning estimate for comparing scenarios. For precise figures, run your actual generation and consumption interval data.

Solar Self-Consumption vs. Export Calculator

When solar generation and household demand are both expressed as daily totals they can look perfectly matched, yet a home can still export most of its solar because the sun peaks at midday and people use power in the evening. This calculator overlays representative hourly curves to estimate what share of your solar you actually use on-site versus send to the grid.

How it works

Generation and load are each spread across 24 hours using a chosen shape, then compared hour by hour:

for each hour h:
  self-consumed[h] = min(generation[h], load[h])
  exported[h]      = max(generation[h] − load[h], 0)

self-consumption % = Σ self-consumed / Σ generation × 100
annual export      = Σ exported × 365

Because the comparison is per hour, midday solar above the daytime load counts as export even if the daily totals are equal — which is exactly the gap a battery can close by shifting that surplus to the evening.

Example and tips

A home generating 20 kWh/day with an afternoon-peaking array but an evening-heavy residential load might self-consume only around 35 to 45 percent, exporting the rest. Flattening or shifting load toward midday raises self-consumption directly. The annual export figure shown is roughly the energy a battery could time-shift, so compare its value at your export rate against the retail savings storage would unlock.