Generation and load at different times
Direct use is 0 kWh. The period contains 10 kWh of generation and 10 kWh of load, but they occur in different intervals. Import and export are both 10 kWh.
PV consumed directly 0 kWh Open in the calculator
Solar self-consumption calculator
Balance paired PV and load readings interval by interval to find direct solar use, grid imports and exports.
1PV generation scale
0consumed directly
2 intervals, first to last from left to right. Vertical scale: 0–10 kWh per interval.
PV generationSite load
PV: 10 kWh
Direct use: 0 kWh
Export: 10 kWh
Import: 10 kWh
Scale the same PV shape to compare array sizes. Import and export are balanced separately in every interval.
PV consumed directly
0kWh
2 aligned intervals covering 2 hours.
Check the values to see a result.
- PV self-consumption
- 0%
- Grid import
- 10 kWh
- Grid export
- 10 kWh
- Load supplied by PV
- 0%
AC energy balance without a battery or export curtailment. Coarse intervals can overstate simultaneous use. No annual extrapolation.
How it’s calculated
- Direct use = sum of min(PV, load) for each interval=2 separate interval balances=0 kWh
- Grid import = load − direct use=10 − 0=10 kWh
- Grid export = PV − direct use=10 − 0=10 kWh
Direct use = sum of min(PV, load) in each interval
0 kWh of 10 kWh PV generation supplies 10 kWh of load directly.
Tip: Hourly or coarser data can overstate coincident use within an interval. Missing, duplicated or misaligned intervals must be corrected before pasting.
Method and boundaries
For each interval, direct solar use is the smaller of PV generation and gross site load. Export is the remaining PV energy, while import is the remaining load. Add these interval balances only after matching timestamps, timezones and measurement boundaries. Use kWh during each interval, not instantaneous kW.
Pair measurements before adding them
For each interval, direct solar use is the smaller of PV generation and gross site load. Export is the remaining PV energy, while import is the remaining load. Add these interval balances only after matching timestamps, timezones and measurement boundaries. Use kWh during each interval, not instantaneous kW.
Distinguish the two percentages
Self-consumption is direct use divided by PV generation. Self-sufficiency is direct use divided by site load. A small array can achieve high self-consumption while supplying only a small share of a building’s demand. If the relevant denominator is zero, the percentage is undefined rather than zero.
Keep the sampling limit visible
An hourly reading cannot reveal changes within the hour. Generation early in an interval and load later in the same interval may look coincident when totals are compared. Shorter, synchronized intervals reduce this effect. No battery, curtailment or export limit is modelled, and the entered period is not extrapolated to a year.
Interval solar self-consumption examples
Partial coincidence in two intervals
Direct use is 3 kWh: 2 kWh in the first interval and 1 kWh in the second. Grid export is 1 kWh and import is 3 kWh. Self-consumption is 75%, while PV supplies 50% of the load.
PV consumed directly 3 kWh Open in the calculator
Questions about Interval solar self-consumption
Can I paste grid import as the load?
No. Use gross site consumption at the same AC measurement boundary as PV. Net import already excludes some local solar use and would understate demand.
Does increasing PV scale size a battery?
No. Scaling preserves the generation shape and compares direct use and surplus. Storage needs a chronological dispatch model with energy, power, efficiency and reserve limits.
Can I compare a week with a year?
Only as separate observed periods. This calculator does not scale a short sample to annual production or annual savings. Seasonality, occupancy and weather can change both generation and demand. Use complete synchronized records across the period you want to assess, and inspect missing values before copying the data.
Limits of this result
- No storage, export cap, clipping or load shifting is modelled. Results apply only to the entered period.
- Use gross site load and PV generation measured at the same AC boundary. Grid import alone is not total site load.
- Hourly or coarser data can overstate coincident use within an interval. Missing, duplicated or misaligned intervals must be corrected before pasting.