How to interpret the various parameters of a photovoltaic monitoring system
This article mainly introduces some commonly used metrics in photovoltaic monitoring systems.
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
Sort and Compare More Than One Solar PV Site in the Solar Analysis
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.
