Why your solar monitoring app and Synergy bill show different numbers

If you've compared your inverter monitoring app to your Synergy bill and found the numbers don't match, you're not misreading either one. They measure completely different things. Understanding the gap tells you whether your system is performing correctly — and whether Synergy is paying you the right DEBS credits.

What your inverter app measures

Your inverter monitoring app (SolarEdge, SMA Sunny Portal, Fronius Solar.web, Sungrow iSolarCloud, Tesla app, etc.) measures total electricity generated by your solar panels. This is the gross production figure — every kWh the panels produce, regardless of where it goes.

Example: Your 6.6kW system generates 11,000kWh in a year. Your inverter app shows: 11,000kWh generated.

What your Synergy bill measures

Your Synergy bill shows two solar-related figures:

DEBS export credits: the kWh you sent to the grid. This is only the surplus solar that the house didn't use — the excess that flowed out through the meter.

Import charges: the kWh you drew from the grid (nights, cloudy days, when solar wasn't enough).

Example (same household): The household consumed 5,000kWh of its own solar generation. It exported 6,000kWh to the grid. Synergy shows: 6,000kWh exported (DEBS credits). The other 5,000kWh was self-consumed — it never appeared on the Synergy meter.

The equation

Generated = Self-consumed + Exported 11,000 = 5,000 + 6,000

The inverter app shows the 11,000. Synergy shows the 6,000. The 5,000 in the middle never appears on either the import or export side of your Synergy bill — it was used directly in your house without touching the grid meter.

This is always the gap, and it's always correct. If your Synergy export figure were equal to your inverter generation figure, it would mean you used zero solar directly — which would require every solar kWh to flow to the grid and back, paying DEBS export rates (2–10c) and re-importing at tariff rates (33c). That's economically backwards; self-consumption is more valuable.

Common scenarios that look confusing but are normal

"My app shows 900kWh generated this month but Synergy only shows 350kWh exported" You self-consumed 550kWh. That's good — every kWh self-consumed at A1 (33.26c) is worth 16× more than exporting at off-peak DEBS (2c/kWh).

"My app shows I exported 500kWh but DEBS on my bill is less than I expected" Check if you're on A1 (no time-of-day export rates) vs Midday Saver/DEBS peak/off-peak split. On Midday Saver, most export is at 2c/kWh (9pm–3pm off-peak) and only peak-window export (3pm–9pm) earns 10c/kWh.

"My app shows 400kWh generated but my DEBS credit is for 380kWh" A small difference (5–8%) between generation and export is normal even on a household that genuinely tried to export everything — battery losses, inverter conversion losses, and DC wiring losses account for 2–5% of generation. 5% self-consumption is realistic even in an empty house (standby power, always-on appliances).

When the gap reveals an actual problem

The self-consumption gap is expected and healthy. But certain patterns indicate something wrong:

Export shown on Synergy is higher than generation shown by inverter: This can't happen normally (you can't export more than you generate). Possible causes: meter calibration error, incorrect tariff coding by Synergy, or the inverter monitoring is under-reporting (firmware issue).

DEBS credits have disappeared from the bill: If DEBS credits were appearing and suddenly stopped, check: Was your smart meter replaced recently? Did Synergy change your tariff coding? Is the export isolator switched to "off"? Contact Synergy to verify the export tariff is still active on the account.

Export is exactly zero despite sunny days: Export limiting — some systems are set to zero-export (network limitation from Western Power in congested areas). Your inverter app will show generation but Synergy shows zero export. Check your inverter settings for "export limit" — if set to 0kW or 0%, it's operating in zero-export mode.

Generation matches export almost exactly (ratio > 95%): Very high export ratio suggests either extremely low household consumption during solar hours, or a monitoring data issue. Also possible: the system was installed recently and the household was vacant for part of the period.

Which figure to trust for which purpose

For checking your system is performing correctly: Use the inverter app generation figure. Compare it to the expected annual generation (system size kW × 1,825 for Perth). Calculate your performance ratio (actual ÷ theoretical). This tells you if the panels and inverter are working.

For checking Synergy is paying you correctly: Use the Synergy bill export figure. Multiply by your DEBS rate and confirm the credit on the bill matches. This tells you if Synergy's meter is recording correctly.

For understanding your electricity cost: Total import on Synergy bill tells you how much grid power you bought. Self-consumption = (inverter generation) − (Synergy export). This self-consumption value at your avoided tariff rate is the largest financial benefit of solar — and it doesn't appear directly on the Synergy bill at all.

Reading the two data sources together

A useful monthly reconciliation:

| Figure | Source | |---|---| | Solar generated | Inverter monitoring app | | Solar exported | Synergy bill (DEBS section) | | Solar self-consumed | Generated minus Exported | | Grid imported | Synergy bill (consumption section) | | Total consumption | Self-consumed + Grid imported |

Running this comparison each month helps you spot anomalies quickly — if self-consumption drops unexpectedly, something changed in your household usage pattern (or the household was on holiday). If export spikes without a corresponding generation increase, investigate the meter.

Upload your Synergy bill to BillWise and enter your inverter generation figure to run the reconciliation automatically and verify your self-consumption rate.