Terms | mc Help Center

Last modified: 2025-11-05

In the mathematical sense, a “term” allows you to define custom data points at the system Level using your own formula, which is evaluated for the variables used for every available timestamp.

The Term editor in VCOM allows you to process measured data from your system and generate key performance indicators. Terms are integral to charts, simulations, KPIs, evaluations, and certain portlets.

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Example

You can use terms to calculate the average for several sensors or to define the parameters to determine the total energy generated (E_Z_EVU).

Create a term

Prerequisites

You belong to the user group technician, operations, or administrator. See User groups.

Steps

At System level , go to System configuration > Calculations > Terms > Term editor.

If necessary, view the available datapoints (= variables) and corresponding terms, and select relevant devices in the Measured values overview. See also Available data points and categories.
Select Term to create a new term.

Define the new term:
- Designation: Give your term a designation. This is a user-friendly name that will later be visible in graphs and reports. The designation is not translated into other languages.
- Abbreviation: Give your term an abbreviation. This defines how the results of this term can be referenced in other terms and through the VCOM API. If possible, use the defined abbreviations. See Terms abbreviations with a special meaning.
- Type (Aggregation): Select how the values that this term yields should be aggregated. Currently, there are two options:
  - Sum: Results are summed up over time (e.g. energy values).
  - Average: Results are averaged over time (e.g. temperature values).
- Unit: Select the unit to be displayed in charts and reports.
  Important: If the unit W/m² is used, the type Average should be selected, as for time intervals greater than one hour, the aggregation will automatically switch to the unit Wh/m².
- Formula: Define a formula for your term, consisting of variables, numbers, operators, and simple or complex functions. See also Formulas. If necessary, read the Documentation or Preview the formula results for the selected day.
Select Save.

The term appears in the list of terms and can now be applied throughout VCOM, for example, in the Power flow portlet and Charts.

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Example

In the example below, the datapoint E_Z_EVU is defined as the energy sum of the inverters.

Further actions

Preview details, Edit, or Delete a term by selecting the term’s corresponding action item in the list of terms.

Recalculation of terms

If you change a term, you may need to recalculate all terms for previous periods.

Caution

Recalculation of terms will overwrite previous values.

Prerequisites

You belong to the user group technician, operations, or administrator. See User groups.

Steps

At System level , go to System configuration > Calculations > Terms > Term editor.
Select Recalculation of terms.
Enter the period for which you want to re-calculate all newly created terms. If the recalculation period exceeds 1 year, you must perform another recalculation.
Select Start recalculation.

All terms are now recalculated for the selected period,, and charts will display the new values.

Abbreviations with a special meaning

You can find a full list of all abbreviations under Measured values overview.

Abbreviation	Required unit	Description	Used in VCOM	Further details
E_Z_EVU	kWh	Energy generated per interval for the whole system.	Simulation Alarms Charts Various KPIs	VCOM’s default definiton is ‘E_INT', which includes all inverters.
E_Z_x (x = 1...99)	kWh	Other energy generated per interval measurements, for example for subsystems.	Comparison of meters chart
G_M0	W/m²	Plane of array irradiance (POAI)	Simulation Charts Various KPIs	If your system has multiple irradiance sensors, select the ones you want to include in the formula for G_M0 at System level , under System configuration > Calculations > Terms in the area Plane of array irradiance (POAI). By default the average of all selected sensors is calculated. If sensors belong to subsystems with different orientations, also select Adjust weighting to reflect that. Caution Do not use satellite irradiance data points to define G_M0. Satellite date is available only with a delay and only on an hourly basis. This would lead to irregularities in KPIs, simulation, and therefore various charts.
G_Mx (x = 1…99)	W/m²	Other plane of array irradiance (POAI) measurements	Simulation
G_H0	W/m²	Global horizontal irradiance (GHI)	Evaluation
G_Hx (x = 1...99)	W/m²	Other global horizontal irradiance (GHI) measurements	Evaluation
M_AC_E_EXP	kWh	Energy grid export	Self-consumption chart	For creating these terms, see Self-consumption terms.
M_AC_E_IMP	kWh	Energy grid import
M_AC_E_OWN	kWh	Energy self-consumption
M_AC_E_CON	kWh	Energy total consumption
B_E_DISCHARGE	kWh	Battery discharging
B_E_CHARGE	kWh	Battery charging
PF_P_GRID	W	Import/export power	Power flow portlet	Create the respective terms by configuring the portlet when you first add it to a tab.
PF_P_CON	W	Consumption power
PF_P_BAT	W	Battery power
T_M0	°C	Module temperature per interval for the whole system	KPIs Charts
T_Mx (x = 1...99)	°C	Other module temperature measurements per interval	Charts
T_Ux (x = 0...99)	°C	Ambient temperature measurements
W_Vx (x = 0…99)	m/s	Wind speed measurements
W_Dx (x = 0…99)	°	Wind direction measurments

Formulas

Variables and data source

You must specify at least one variable for each formula otherwise nothing will be calculated. VCOM provides you with an overview of the available datapoints (= variables) and the corresponding terms for your system. For this, select Measured values overview while editing a term. In general, all variables start and end with an apostrophe ('). Any configured device can be selected separately via the dropdown menu. If no device is selected, the sum of all devices will be taken.

Available data sources (variables) — Available data sources (=variables)

Notes

The result of the term is not tied to a specific device; even if it uses the values from one device, it applies to the entire system and is not associated with any particular device.
For the sake of simplicity, the example used below will not use variables and use NULL to represent a null-value returned by a variable or calculation.

Numbers

In addition to variables, numbers can be used. Both , and . can be used as a decimal separator. Thousands separators and scientific notation are not supported.

Operators

To combine multiple variables (and numbers), various operators are available. In general, all operators will yield null if any of the operands are null, the only exception of that rule being ??. The precedence describes the order of calculation, with higher precedence evaluated before lower precedence

List of operators

Precedence	Symbol	Name	Description	Example
				Formula	Result
8	`(` `)`	Parenthesis	Pairs must be balanced. Other types of parenthesis like `[` `]` or `{` `}` are not supported.	`2 * (2 + 3)`	`10`
7	`!`	Boolean-Negation	Returns `0` for `1` and `0` for everything else. This is a unary operator to be placed in front of the operand.	`!0` `!1` `!(-1)`	`1` `0` `0`
7	`-`	Arithmetic-Negation	Returns the arithmetic negation of the variable. This is a unary operator to be placed in front of the operand.	`-0` `-1` `-(-1)`	`0` `-1` `1`
6	`^`	Exponentiation	Returns the left operand to the power of the right operand.	`2 ^ 3` `NULL ^ 3` `2 ^ NULL`	`8` `NULL` `NULL`
5	`*`	Multiplication	Returns the product of the two operands.	`2 * 3` `NULL * 3` `2 * NULL`	`6` `NULL` `NULL`
5	`/`	Division	Returns the left operand divided by the right operand. Returns `null` if the right operand is `0` .	`2 / 4` `NULL / 3` `2 / NULL` `2 / 0` `NULL`	`0.5` `NULL` `NULL` `NULL`
5	`%`	Remainder	Returns the remainder of dividing the left operand by the right operand. Returns `null` if the right operand is `0` .	`2 % 4` `NULL % 3` `2 % NULL` `2 % 0`	`2` `NULL` `NULL` `NULL`
4	`+`	Addition	Returns the sum of both operands.	`2 + 3` `NULL + 3` `2 + NULL`	`5` `NULL` `NULL`
4	`-`	Subtraction	Returns the the second operand subtracted from the first operand.	`2 - 3` `NULL - 3` `2 - NULL`	`-1` `NULL` `NULL`
3	`==`	Equality	Returns `1` if the left operand is equal to the right operand, `0` otherwise.	`2 == 2` `2 == 3` `2 == NULL` `NULL == NULL`	`1` `0` `NULL` `NULL`
3	`!=`	Non-equality	Returns `0` if the left operand is not equal to the right operand, `1` otherwise.	`2 != 3` `2 != 2` `2 != NULL` `NULL != NULL`	`1` `0` `NULL` `NULL`
3	`<`	Less-Than	Returns `1` if the left operand is strictly less than the right operand, `0` otherwise.	`2 < 3` `2 < 2` `2 < NULL` `NULL` `NULL < NULL`	`1` `0` `NULL` `NULL`
3	`>`	Greater-Than	Returns `1` if the left operand is strictly greater than the right operand, `0` otherwise.	`2 > 1` `2 > 2` `2 > NULL` `NULL > NULL`	`1` `0` `NULL` `NULL`
3	`<=`	Less-Or-Equal	Returns `1` if the left operand is less or equal to the right operand, `0` otherwise.	`2 <= 3` `3 <= 2` `2 <= NULL` `NULL <= NULL`	`1` `0` `NULL` `NULL`
3	`>=`	Greater-Or-Equal	Return `1` if the left operand is greater or equal to the right operand, `0` otherwise.	`2 >= 2` `2 >= 3` `2 >= NULL` `NULL >= NULL`	`1` `0` `NULL` `NULL`
2	`&&`	Logical And	Returns `1` if both operands are not `0` , `0` otherwise.	`1 && 1` `1 && 0` `0 && 0` `NULL && 1`	`1` `0` `0` `NULL`
2	`\|\|`	Logical Or	Returns `1` if either operand is not `0` , `0` otherwise.	`1 \|\| 1` `1 \|\| 0` `0 \|\| 1` `0 \|\| 0` `NULL \|\| 1`	`1` `1` `1` 0 `NULL`
1	`??`	Null-Coalesce	Returns the value of the left operand if it is not `null` , otherwise the right operand is returned.	`0 ?? 1` `NULL ?? 1`	`0` `1`

Functions

In addition to operators, functions can greatly reduce the complexity of formulas. Functions calls consist of a function identifier, followed by a list of parameters (separated by ; ) in parenthesis ( ). Calling functions with fewer/more parameters than required is an error.

Simple functions

List of simple functions

Identifier	Number of parameters	Description	Example
			Formula	Result
`sum`	2-999	Returns the sum of all non-`null` parameters, `null` if there are none.	`sum(3; 3)` `sum(2; NULL)` `sum(NULL; NULL)`	`6` 2 `NULL`
`average`	2-999	Returns the mean of all non-`null` parameters, `null` if there are none.	`average(2; 4)` `average(10; NULL; 30)` `average(NULL; NULL)`	`3` `20` `NULL`
`median`	2-999	Returns the median of all non-`null` parameters, `null` if there are none.	`median(7; 3; 5)` `median(7; NULL; 5)` `median(NULL; NULL)`	`5` `6.5` `NULL`
`min`	2-999	Returns the smallest of all non-`null` parameters, `null` if there are none.	`min(-1; 5; 3)` `min(NULL; 5; 3)` `min(NULL; NULL)`	`-1` `3` `NULL`
`max`	2-999	Returns the greatest of all non-`null` parameters, `null` if there are none.	`max(-1; 5; 3)` `max(-1; NULL; 3)` `max(NULL; NULL)`	`5` `3` `NULL`
`pi`	0	Returns the value of pi.	`pi()`	`3.1415926535898`
`sin`	1	Returns the sine of the parameter, the parameter has to be given in radians, not degrees. Returns `null` if parameter is `null` .	`sin(pi()/2)` `sin(0)` `sin(NULL)`	`1` `0` `NULL`
`cos`	1	Returns the cosine of the parameter, the parameter has to be given in radians, not degrees. Returns `null` if the parameter is `null` .	`cos(pi())` `cos(0)` `cos(NULL)`	`-1` `1` `NULL`
`if`	2-3	Returns the second parameter if the first parameter is not `0` or `null`, otherwise returns the third parameter (if given) or `null` otherwise.	`if(1; 2)` `if(0; 2)` `if(NULL; 2)` `if(-1; 2; 3)` `if(0; 2; 3)` `if(NULL; 2; 3)`	`2` `NULL` `NULL` `2` `3` `3`
`select`	2-999	Returns the n-th parameter after the first parameter, where the value of `n` is the first parameter, `null` if no parameter is found.	`select(1; 2; 3; 4)` `select(2; 2; 3; 4)` `select(3; 2; 3; 4)` `select(4; 2; 3; 4)`	`2` `3` `4` `NULL`
`take_positive`	1	Returns the first parameter if it is strictly greater than zero, `null` otherwise.	`take_positive(5)` `take_positive(0)` `take_positive(-3)` `take_positive(NULL)`	`5` `NULL` `NULL` `NULL`
`weighted_average`	4..998 (only even) first-value; first-weight; second-value; second-weight;...	Returns the weighted mean of all non-`null` values, `null` if any of the weights are `null` or there are no values.	`weighted_average(25; 2; 10; 1)` `weighted_average(25; 2; NULL; 1)` `weighted_average(25; 2; 10; NULL)` `weighted_average(NULL; 2; NULL; 1)NULL`	`20` `25` `NULL` `NULL`

Complex functions

List of complex functions

Identifier	Number of parameters	Description	Example
			Timestamp	Formula	Result
`year`	0	Returns the current year	`2024-02-09 12:00:00`	`year()`	`2024`
`month`	0	Returns the current month of year (1-12)	`2024-02-09 12:00:00`	`month()`	`2`
`day`	0	Returns the current day of month (1-31)	`2024-02-09 12:00:00`	`day()`	`9`
`before`	1-6 year; month = 1; day = 1; hour = 0; minute = 0; second = 0	Returns `1` if the currently evaluated timestamp is strictly before the date given as parameters, `0` otherwise	`2023-12-31 23:59:59` `2024-01-01 00:00:00`	`before(2024)` `before(2024)`	`1` `0`
`after`	1-6 year; month = 1; day = 1; hour = 0; minute = 0; second = 0	Returns 1 if the currently evaluated timestamp is strictly after the date given as parameters, `0` otherwise.	`2023-12-31 23:59:59` `2024-01-01 00:00:00`	`after(2023; 12; 31; 23; 59; 59)` `after(2023; 12; 31; 23; 59; 59)1`	`0` 1
`before_time`	1-3 hour; minute = 0; second = 0	Returns `1` if the currently evaluated timestamp's time is strictly before the time given as parameters, `0` otherwise.	`04:59:59` `05:00:00`	`before_time(5)` `before_time(5)`	`1` `0`
`after_time`	1-3 hour; minute = 0; second = 0	Returns`1` if the currently evaluated timestamp's time is strictly after the time given as parameters, `0` otherwise.	`19:59:59` `20:00:00`	`after_time(19; 59; 59)` `after_time(19; 59; 59)`	`0` `1`
`is_monday` `is_tuesday` `is_wednesday` `is_thursday` `is_friday` `is_saturday` `is_sunday`	0	Returns `1` if the currently evaluated timestamp is on a monday/tuesday/wednesday/thursday/friday/saturday/sunday, `0` otherwise	`2024-02-09 00:00:00` `2024-02-09 23:59:59` `2024-02-10 00:00:00`	`is_friday()` `is_friday()` `is_friday()`	`1` `1` `0`
`sun_up`	0	Returns `1` if the sun is over the horizon, `0` otherwise. *The actual result depends on the time and location of the system.	`2024-02-09 07:30:00` `2024-02-09 07:35:00` `2024-02-09 17:25:00` `2024-02-09 17:30:00`	`sun_up()` `sun_up()` `sun_up()` `sun_up()`	`0` * `1` * 1 * `0` *
`sun_azimuth`	0	Returns the sun's azimuth angle in degrees (0=North, 180=South) at the currently evaluated timestamp. *The actual result depends on the time and location of the system.	`2024-02-09 07:30:00` `2024-02-09 12:00:00` `2024-02-09 17:30:00`	`sun_azimuth()` `sun_azimuth()` `sun_azimuth()`	`110` * `171.74` * `250` *
`sun_elevation`	0	Returns the sun's elevation angle between horizon and the sun in degrees at the currently evaluated timestamp. *The actual result depends on the time and location of the system.	`2024-02-09 12:00:00`	`sun_elevation()`	`26.54` *
`delta`	1-3 total; negative-limit = -∞; positive-limit = ∞	Returns the difference between this timestamp's first parameter and the last timestamp's first parameter, `null` if outside of limits. ¹ The first result of the `delta` function on each day is always `NULL` ² If the passed total is `NULL` , the last total is re-used for the next evaluation	`2024-02-09 00:00:00` `2024-02-09 00:05:00` `2024-02-09 00:10:00` `2024-02-09 00:15:00` `2024-02-09 00:20:00`	`delta(50)` `delta(60)` `delta(50)` `delta(NULL)` `delta(60)`	`NULL` ¹ `10` `-10` `NULL` ² `10`
`tilted_irradiance`	3	Returns the tilted irradiance calculated from the horizontal irradiance value (the first parameter), the tilt of the surface (the second parameter) and the orientation of the surface (the third parameter), `null` if either parameter is `null` . *The actual result depends on the time and location of the system.		`tilted_irradiance(800; 20; 180)` `tilted_irradiance(NULL; 20; 180)` `tilted_irradiance(800; NULL; NULL)`	`926` * `NULL` `NULL`