Industrial solar PV · technical guide
Reverse-power protection for industrial solar PV
Industrial behind-the-meter (BTM) solar PV systems may not feed back into the grid — the distribution system operator requires reverse-power protection. This requirement fundamentally shapes system sizing, orientation and payback. Below we explain, from an installer’s perspective, what reverse power flow is, what protection options exist, and how the constraint can be turned into an advantage.
Why does reverse power flow occur?
Solar generation peaks during the day — around midday the system may run at its rated output. If site consumption is lower at that moment (lunch break, weekend, shutdown, seasonal decline), the surplus would flow towards the grid. On an industrial BTM connection this is not permitted: the grid connection agreement prohibits or limits feed-in, and it is also a risk from a network protection perspective.
Reverse power flow is therefore not a fault but a consequence of sizing — and the larger the system relative to consumption, the more often it occurs.
Behind-the-meter system — BTMBehind-the-meter: an on-site system on the customer side of the meter that cannot export to the grid.More in the glossary →
Industrial solar PV generates on the site side of the meter and serves the site’s own consumption.
Curtailed surplus — clippingDC generation above the inverter AC rating that cannot be used — capturable with a BESS.More in the glossary →
Whatever is not used on site and cannot go to the grid is lost — unless battery storage captures it.
The three levels of protection
1. Sizing and orientation — prevention
We size the system for self-consumption, not for the roof area. With an east–west orientation the generation peak spreads into the morning and afternoon: around 8–10% less annual generation, in exchange for a higher self-consumption ratio and far fewer reverse-power events. On flat roofs this is the industrial standard.
2. Active export limitation — the mandatory protection
Directional metering at the connection point plus inverter-level output control (zero export). If the meter detects feed-in, the inverters throttle back within seconds. This is the standard way of meeting the DSO requirement — but the curtailed energy is lost.
3. Battery storage — putting the surplus to work
The BESS absorbs the surplus that would otherwise be curtailed as free charging, then discharges it towards the site during the more expensive hours. The constraint thus becomes a source of value: storage is the only solution where surplus generation is not lost.
Industrial battery storage →How much generation is at stake?
The loss caused by reverse-power limitation depends on the relationship between the consumption profile and the system size. The exact figure can only be determined by a simulation run on the site’s 15-minute consumption data — our engine calculates across 35,040 intervals using the actual generation curve.
- •For a well-sized industrial system, the typical loss range is 2–8% per year.
- •For plants that shut down at weekends, or oversized systems, it can reach 15–25%.
- •The simulation shows how much is curtailed, what it is worth with battery storage, and what the optimal system size is.
Frequently asked questions
What is reverse power flow?+
Reverse power flow occurs when the solar PV system generates more than the site is consuming at that moment — the surplus would flow back towards the grid. On an industrial behind-the-meter (BTM) connection sized for self-consumption, feed-in is not permitted, so the distribution system operator requires reverse-power protection.
How does reverse-power protection work?+
Power metering at the connection point continuously monitors the direction of energy flow. If it starts to turn towards feed-in, the control system throttles the inverters’ output within seconds (to zero or to the permitted level). The solution is built from the inverter manufacturer’s output controller (export limitation / zero export function) and a directional meter.
How much generation is lost to reverse-power limitation?+
The loss depends on the relationship between system size and consumption profile. For a system well sized for self-consumption it is typically 2–8% per year; for an oversized system or a plant that shuts down at weekends it can reach 15–25%. The exact figure can be determined by a simulation run on 15-minute consumption data — we prepare this free of charge.
Related pages
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