Peak Shaving and Grid Charge Modelling – SolarPlus Help Centre

Peak-Shaving & Discharge Gates

User guide for solar engineers (no code required)

1. Key concepts

Term	What it means in practice	Typical value
Peak-shaving limit (Peak Lopping Threshold)	Maximum grid import you want to see at the site meter. The battery will step in to keep the feeder at or below this kW level.	e.g. 60 kW for a 63 kVA service
Shaving SoC set-point	The reserve state-of-charge the battery must keep ready for peaks. While the pack is at or below this %, it stays in “peak-shave reserve” and only discharges to shave peaks. Once it rises above the set-point, the system is free to self-consume.	100 % → always in shave-reserve. 80 % → self-consume whenever SoC > 80 %.
Gross-charge SoC limit	Low-battery floor below which the pack will charge (from PV or grid) before doing anything else.	Module-maker minimum, e.g. 10 %
Grid-charge schedule	Periods when a timer or optimisation routine is actively charging from the grid (cheap tariffs, curtailment credits, etc.). During these windows the battery will not discharge unless a genuine peak event forces it.
Tariff battery stop	Utility rule that forbids discharge in certain tariff blocks (e.g. shoulder or off-peak). When on, the pack simply sits idle unless grid outage backup is required.

2. Operating states

State	What the battery is doing	Trigger
CHARGE	Absorbing surplus PV or grid energy to lift SoC above the low-floor.	SoC ≤ gross-charge limit.
SHAVING	Discharging just enough to cap feeder power at the peak-shaving limit.	Both conditions: 1) feeder kW would exceed limit and 2) SoC in the shave-reserve band (≤ set-point).
DISCHARGE (self-consumption)	Covering local load to minimise grid import.	SoC > shave set-point and no tariff / grid-charge block active.
NONE (idle)	Battery is neither charging nor discharging.	• Surplus PV already meets load • Tariff stop active • Timer charging active • In reserve but no peak event.
BACKUP	Discharging regardless of other rules.	Site is off-grid (grid outage).

3. How the decisions flow each hour

Safety / backup checks
- Grid outage → BACKUP.
- Surplus export or timer lockout → NONE.
- SoC below gross-charge limit → CHARGE.
Peak-shave assessment
- Calculate feeder import (load – PV).
- If it would exceed the limit and the battery is still in the reserve band (SoC ≤ set-point) → SHAVING.
Normal run (no peak event)
- If SoC is above the reserve set-point:
  - DISCHARGE unless a tariff stop or grid-charge schedule blocks it.
- If SoC is in reserve and no peak event is present → stay NONE.

4. Practical tuning tips

Set the peak limit first.
Match it to the site’s contractual demand cap or the capacity where network charges step up.
Choose the reserve set-point to balance goals
- 100 % – maximum demand protection; battery only responds to peaks.
- 80-90 % – still holds ample headroom yet allows daily self-consumption once charged.
- 50-70 % – prioritises bill savings through self-use; peak shaving available provided SoC hasn’t been run too low.
Verify tariff interactions.
If the utility forbids discharge in shoulder or off-peak periods, enable Tariff Battery Stop for those blocks; the battery will ignore self-consumption and shaving unless the feeder truly exceeds the cap.
Consider timer-based grid charging
Charging cheaply overnight can refill the reserve for morning peaks; just remember the timer block suppresses discharge except during an active peak event.
Check low-SoC behaviour.
In long cloudy stretches the pack may dip below the gross-charge floor, forcing a grid top-up before any further discharge. Make sure the floor suits battery warranty limits.

5. Quick checklist when results look odd

Is the feeder really above the limit?
Compare “Import kW” in the raw output with the peak-shaving threshold.
Is SoC in the reserve band?
Below or equal to the set-point → eligible to shave. Above → system will self-consume instead.
Is a tariff stop or grid-charge timer active?
Either will block ordinary discharge.
Gross-charge floor?
If SoC is below the low floor the battery will only charge.
Backup mode triggered?
During a grid outage, all other rules are bypassed and the pack discharges to meet load.

Keep these rules in mind and you’ll be able to predict – and confidently explain to clients – exactly why the battery acted the way it did at any time of day.