FAQ
TL;DR: 20–30% higher "consumption" after PV meter swaps was reported [Elektroda, Slak68, post #18772107] "Turn off the inverter and check P+/P-." [Elektroda, bryko, post #18770413] Misdirected phases or reversed wiring can make export count as import [Elektroda, rfneo, post #20336513]
Why it matters: This FAQ helps PV owners diagnose bi‑directional meter readings that suddenly look too high and avoid paying for energy they actually exported.
Quick Facts
- OBIS 1.8.0 = total import (from grid); 2.8.0 = total export (to grid). These are standard codes. “IEC 62056-61 OBIS codes”
- Iskra AM550 is a bidirectional smart meter used by DSOs; it logs import/export per OBIS. “Iskra AM550 Technical Description”
- Typical residential self-consumption without storage: approx. 20–40% of PV production. [Fraunhofer ISE, 2023]
- PV summer yield in Central Europe: approx. 4–6 kWh/kWp/day. “PVGIS — Photovoltaic Geographical Information System”
- You can request a DSO meter verification; if the meter is correct, a fee may apply. “PGE Dystrybucja — Meter verification”
Why does my electricity use look higher after installing PV?
Common causes include miswired phases or reversed meter connections, which swap import and export. Users reported 20–30% higher indicated use after meter swaps [Elektroda, Slak68, post #18772107] One case was confirmed: phase L1 reversed at the meter, fixed by the operator [Elektroda, rfneo, post #20336513] Also check OBIS 1.8.0 (import) and 2.8.0 (export) to separate usage from production. “IEC 62056-61 OBIS codes”
What do OBIS 1.8.0 and 2.8.0 on my meter mean?
OBIS 1.8.0 is cumulative energy imported from the grid. OBIS 2.8.0 is cumulative energy exported to the grid. Many DSOs and meters, like Iskra AM550, use these exact identifiers. “IEC 62056-61 OBIS codes”; “Iskra AM550 Technical Description”
How do I quickly test if my meter is counting in the wrong direction?
- Turn off the inverter; check the meter’s instantaneous power: it should show P+ (import) if you have load [Elektroda, bryko, post #18770413]
- Turn on a known large load at night; verify that 1.8.0 rises, not 2.8.0 [Elektroda, rfneo, post #18830860]
- Power the inverter back on; with sunny load off, 2.8.0 should rise. “Iskra AM550 Technical Description”
Can reversed phase or wiring really bill my exports as imports?
Yes. One user observed export increasing when turning on loads at night; the DSO confirmed reversed wiring on phase 1. After correction, readings were normal [Elektroda, rfneo, #18830860; Elektroda, rfneo, #20336513]. Expert tip: “Turn off the inverter for a moment and see if the meter shows P+ or P-.” [Elektroda, bryko, post #18770413]
Does phase order matter with a 3‑phase inverter and meter?
Yes. The meter expects phases in a defined order; incorrect phase sequence or swapped conductors can misassign import/export per phase. That can skew totals. Correct phase mapping is part of AM550 installation. “Iskra AM550 Technical Description”; [Elektroda, rfneo, post #20336513]
How much should a 4.5–6 kWp system produce in summer?
Typical summer output is about 4–6 kWh per kWp per day. A 4.5 kWp system yields roughly 18–27 kWh/day. Over 14 days, expect about 250–380 kWh. One 5.94 kWp system produced 319 kWh in ~11 days [Elektroda, rfneo, post #18829880] “PVGIS — Photovoltaic Geographical Information System”
Why do I see import while producing power?
Meters and inverters work per phase. If your loads are on different phases than your PV export, the meter can show simultaneous import and export. Some meters sum per phase internally. Align loads or use a 3‑phase inverter to balance. “Iskra AM550 Technical Description”; [Elektroda, theo33, post #18769806]
How should I document the issue before calling the DSO or installer?
Record daily OBIS 1.8.0 and 2.8.0 values with timestamps and weather notes. Photograph the meter display when performing the inverter off/on test showing P+ or P-. Log inverter production for the same periods. Bring evidence of anomalies like export rising at night under load [Elektroda, bryko, #18770413; Elektroda, rfneo, #18830860].
What exactly should I tell the DSO technician?
Report suspected reverse connection on a specific phase, with times and readings. Mention that 2.8.0 increases under nighttime load or that imports rise disproportionately to inverter production. This mirrors a confirmed case fixed by rewiring phase 1 [Elektroda, rfneo, #20336513; Elektroda, rfneo, #18830860].
Could my inverter be wrong while the meter is right?
Expect small differences; revenue meters are MID‑approved, while inverter counters are not revenue grade. Wiring and conversion losses add variance. Use the meter’s OBIS totals as the settlement reference. “Directive 2014/32/EU (MID)”; “Iskra AM550 Technical Description”
How do I read P+ and P- on my smart meter?
Cycle the display to instantaneous power. P+ means you import from the grid; P- means you export. During daytime PV output with minimal load, you should see P-. With the inverter off and loads on, you should see P+ [Elektroda, bryko, post #18770413] “Iskra AM550 Technical Description”
What if the DSO says the usage is correct but it looks wrong?
Request a formal meter verification. If results confirm a compliant meter, fees may apply. If faults are found, the DSO should correct wiring and adjust billing as per policy. Keep your measurement log for dispute resolution. “PGE Dystrybucja — Meter verification”; [Elektroda, Slak68, post #18772107]
Will a 1‑phase inverter on a 3‑phase supply inflate my imports?
It can. If PV exports on one phase while big loads run on others, the meter can still register imports on those phases. A 3‑phase inverter or load shifting reduces this effect [Elektroda, theo33, post #18769806] “Iskra AM550 Technical Description”
Can I sanity‑check with my own control meter or monitor?
Yes. Install a DIN‑rail meter (e.g., SDM630) or a 3‑phase monitor (e.g., Shelly 3EM) at the main board. Ensure correct CT orientation and phase mapping to avoid inverted readings. Compare its import/export with OBIS totals. “Shelly 3EM Documentation”; “Iskra AM550 Technical Description”
Edge case: why did export increase when I turned on appliances at night?
That indicates reversed wiring or swapped phase direction. One user saw 2.8.0 rise when turning on the oven, kettle, and iron at night; the DSO confirmed reversed phase 1 and fixed it [Elektroda, rfneo, #18830860; Elektroda, rfneo, #20336513].
