Zero export and self-consumption case study
Scope
This case study shows a grid-tied site with PV and a battery. Plant control operates the site for zero export and self-consumption. PV and the battery supply the load first. The grid is the last source.
The data comes from the site dashboard, 1 to 20 October 2026. For the settings, see How plant control works. For a grid import limit at set times, see Shave a demand peak.
The site
| Item | Value |
|---|---|
| Grid connection | One energy meter at the grid point |
| PV | One PV inverter, maximum of 32.8 kW in the case study |
| Battery | One battery converter and one battery bank, approximately 486 kWh |
| Load | Base load of approximately 1 kW, short increases to 85 kW |
| Generator | None |
The settings
The site uses the settings in the table. Plant control can also change the PV output.
| Point | Tab | Setting | Value |
|---|---|---|---|
| Grid | Target Power | Default | 0 |
| Grid | Max Limit | Default | 0 |
| Grid | Min Limit | Default | 0 |
| Storage | Target Power | Default | -100000 |
| Storage | Target Power | Grid/Storage Priority | 5 |
- Grid/Storage Priority: the storage priority (5) is higher than the grid priority (0). Thus the battery controls the AC loop.
- Storage Target Power: -100000 W is a charge of 100 kW. This value is more than the PV can supply. Thus the battery always tries to charge.
- Max Limit 0: the maximum grid import is 0 W. The battery does not charge from the grid. When the load is more than the PV, the battery supplies power.
- Min Limit 0: the maximum grid export is 0 W. When the battery cannot charge more, plant control decreases the PV output.
How the site operates
Plant control examines the grid power in each control cycle. Then it changes the battery power and the PV power.
| Condition | Battery | PV | Grid |
|---|---|---|---|
| PV more than load | Charges with the PV power that the load does not use | Full output | Approximately 0 |
| PV more than load, battery full | Stops | Decreased to the load | Approximately 0 |
| PV less than load | Supplies the difference | Full output | Approximately 0 |
| No PV | Supplies the load | No output | Approximately 0 |
| Load more than PV and battery | At its maximum | Full output | Supplies the difference |
A day with large loads: 19 October
The load had three large increases, at approximately 09:30, 12:00 and 13:30. The highest load was 84.7 kW at 09:33.
- At 09:40: the battery supplied 70.2 kW. PV supplied the difference. The grid stayed near 0 kW.
- Between the large loads: the battery charged with the PV power that the load did not use. The highest charge was 33.4 kW at 11:30.
- From 17:00 to 06:00: the battery supplied the base load of 0.7 kW to 0.9 kW.
- State of charge (SoC): 58% at 00:00, 34% at 23:59.
| Monthly Interval Energy, 19 October | kWh |
|---|---|
| PV | 79.3 |
| Load | 146.2 |
| Storage Charge | 39.2 |
| Storage Discharge | 82.1 |
| Grid Import | 6.9 |
| Grid Export | 3.4 |
The load used 66.9 kWh more energy than the PV supplied. The battery supplied 82.1 kWh. The grid supplied only 6.9 kWh, 5% of the load.
A day with a high PV output and a small load: 17 October
PV supplied 111.1 kWh. The load used 76.2 kWh. The battery charged with all of the PV power that the load did not use.
- From 08:00 to 14:00: PV supplied up to 22.8 kW (two-hour average). The battery charged at up to 21.1 kW.
- SoC: 50% at 08:00, 77% at 16:00.
- Grid: between -0.2 kW and 0.2 kW for all of the day.
The battery did not become full. Thus plant control did not decrease the PV.
A day with a low PV output: 13 October
PV supplied 15.4 kWh. The load used 35.9 kWh.
- From 00:00 to 06:00 and from 16:00 to 23:59: the battery supplied the base load.
- From 08:00 to 12:00: the battery power was 0 kW. The grid supplied 0.5 kW to 0.6 kW (two-hour average).
- From 12:00 to 16:00: the battery charged at up to 2.7 kW (two-hour average). From 12:00 to 14:00, the grid supplied 1.5 kW.
- SoC: 29% at 00:00, 24% at 23:59.
- Grid: 10.0 kWh import, the highest of the month.
The month: 1 to 20 October
| Monthly Interval Energy, 1 to 20 October | kWh |
|---|---|
| PV | 1500 |
| Load | 1700 |
| Grid Import | 134.9 |
| Grid Export | 119.4 |
| Storage Discharge | 672.5 |
- Grid Import: 5.4 kWh to 10.0 kWh each day. This is 8% of the load.
- Grid Export: 1.7 kWh to 11.5 kWh on most days.
- PV and battery: PV and the battery supplied 92% of the load.
What the case study shows
- Grid near 0 kW: plant control held the grid near 0 kW for all of the period. This also occurred with a load of 85 kW.
- Small grid energy: some import and some export occur. The grid power moves around 0 kW between control cycles.
- The battery is the energy store: the battery charges from PV. The battery supplies the load when the PV output is low and during large loads.
- Charge from PV: the battery charges from PV. After some days with a low PV output, the SoC stays low.
If the battery becomes almost empty, over-discharge protection starts an emergency charge. This charge ignores the grid limits, so the grid can charge the battery. See Battery protection settings field definitions.
Tips and Gotchas
- The storage Target Power must be more than the maximum PV power. If it is less, the battery does not charge with all of the PV power, and plant control decreases the PV.
- The storage priority must be equal to or higher than the grid priority. If the grid has the higher priority, the battery follows the grid Target Power.
- The Max Limit and the Min Limit are control targets, not breakers. If the battery is at its maximum, the grid supplies the difference.
- Max Limit 0 stops a usual charge from the grid, but not an emergency charge. For a minimum SoC, add a rule on the storage Target Power. See Build a rule list.
- The Monthly Interval Energy chart can show an incorrect value after a short, large change in the data. On 13 October, the chart shows 177.5 kWh Storage Charge. But the battery charged at 2.7 kW or less.