How to interpret the various parameters of a photovoltaic monitoring system
This article mainly introduces some commonly used metrics in photovoltaic monitoring systems.
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1. Yield and Consumption
This graph shows the KPIs of your solar PV system.
Yield Energy: If you set any meter/CT as "Inverter" type, the energy measured is "Yield Energy" (kWh). IAMMETER calculates this in a preset billing cycle. For the calculation method, refer to Yield Energy Calculation.
Exported Energy: If you set any meter/CT as "Grid" type, the energy exported to the grid is "Exported Energy" (kWh). IAMMETER calculates this in a preset billing cycle. For the calculation method, refer to Exported Energy Calculation.
Grid Consumption: If you set any meter/CT as "Grid" type, the energy imported from the grid is "Grid Consumption" (kWh). IAMMETER calculates this in a preset billing cycle. For the calculation method, refer to Grid Consumption Calculation.
Direct Self-Use: Direct Self-Use (kWh) = Yield Energy - Exported Energy.
Direct Self-Use Rate: Direct Self-Use Rate = Direct Self-Use Energy / Yield Energy.
Income: Income = Exported Power Tariff * Exported Energy.
Savings: Savings = Imported Power Tariff * Direct Self-Use.
Bill: Bill = Imported Power Tariff * Grid Consumption.
2. Power
Inverter Power: Output power of the solar inverter, measured by the meter/CT set as "Inverter" type.
Feed-in Power: Power exported to the grid when positive; power imported when negative, measured by the meter/CT set as "Grid" type.
Load Power: Load Power = Inverter Power - Feed-in Power, calculated automatically by IAMMETER.
3. Current State
This graph shows the energy flow of your solar PV system. See below for the coding for better understanding.
var r = 0; // 0: no flow, 1: A->B, 2: B->A
switch (i) {
case 1: // inverter-feedin
if (inverter > 0 && feedin > 0) r = 1;
break;
case 2: // inverter-load
if (inverter > 0 && load > 0) r = 1;
break;
case 3: // inverter-battery
if (battery > 0 && (inverter - load) > 0) r = 1;
break;
case 4: // load-feedin
if (inverter >= load) {
r = 0; // No need to import energy from grid
break;
} else {
if (feedin < 0 && load > 0) r = 2;
}
break;
case 5: // load-battery
if (battery < 0 && load > 0) r = 2;
break;
case 6: // feedin-battery
if (feedin < 0 && (inverter - load) < battery && battery > 0) r = 1;
break;
default:
break;
}
4. Yield
Yield Energy: If you set any meter/CT as "Inverter" type, this is measured as "Yield Energy" (kWh). IAMMETER calculates it in a preset billing cycle. For the calculation method, refer to [Yield Energy Calculation](#Ref 2).
Exported Energy: If set as "Grid" type, this is measured as "Exported Energy" (kWh). IAMMETER calculates it in a preset billing cycle. For the calculation method, refer to Exported Energy Calculation.
Direct Self-Use: Direct Self-Use (kWh) = Yield Energy - Exported Energy.
IAMMETER calculates Yield Energy, Exported Energy, and Direct Self-Use Energy over selected time periods (Day, Month, Year, or All Year).
5. Consumption
Grid Consumption: If set as "Grid" type, this is measured as "Grid Consumption" (kWh). IAMMETER calculates this in a preset billing cycle. For the calculation method, refer to Grid Consumption Calculation.
Direct Self-Use: Direct Self-Use (kWh) = Yield Energy - Exported Energy.
IAMMETER calculates Grid Consumption and Direct Self-Use Energy over selected time periods (Day, Month, Year, or All Year).
6. Energy Balance
Exported Energy: If set as "Grid" type, this is measured as "Exported Energy" (kWh). IAMMETER calculates this in a preset billing cycle. For the calculation method, refer to Exported Energy Calculation.
Grid Consumption: If set as "Grid" type, this is measured as "Grid Consumption" (kWh). IAMMETER calculates this in a preset billing cycle. For the calculation method, refer to Grid Consumption Calculation</a).
IAMMETER calculates Grid Consumption and Exported Energy over selected time periods (Day, Month, Year, or All Year).
Reference
Solution: Monitor your solar PV system
Sort and Compare More Than One Solar PV Site in the Solar Analysis
Part 1: Insight into Your Photovoltaic System
Part 2: Optimizing Your Photovoltaic System
Ref 1: Meter/CT Type and Energy, Power, and Power Tariff (Import & Export)
- Yield Energy (kWh) & Inverter Power (W): Meter/CT type → Inverter
- Export Energy (kWh), Grid Consumption (kWh), & Feed-in Power (W): Meter/CT type → Grid
Ref 2: How IAMMETER Calculates the Total kWh in a Selected Time Period (Hour, Day, Month, Year)
Total kWh = First kWh data logged in next time period - First kWh data logged in current time period.
Here is a simple example. In the demo account:
- On the left graph, the Total Yield Energy is 4.9 kWh from 9 am to 10 am.
- On the right table, the first kWh data logged @ 9:02:05 is 39262.5 kWh, and at 10:02:06 it is 39267.4 kWh.
39267.4 - 39262.5 = 4.9. Therefore, the Total Yield Energy is 4.9 kWh from 9 am to 10 am. The same calculation applies to daily, monthly, or yearly energy totals.
