# 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.

![How to Calculate the Hourly Energy Data in IAMMETER System](https://iammeterglobal.oss-accelerate.aliyuncs.com/img/iammeter