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Sum values in a list: sum

The sum filter adds up all the values in a list and returns the total. You can optionally specify an attribute to sum a specific property from each item, and a start value to begin the summation from.

This is useful whenever you need to total up numeric values from sensorsSensors return information about a thing, for instance the level of water in a tank. [Learn more] or entitiesAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more]. For example, you might want to calculate total energy consumption across multiple meters, sum up the brightness values of all lights, or add up the number of items detected by multiple sensors. It works well at the end of a filter chain after extracting and converting values to numbers.

Usage

Here’s how to use this template function. Copy any example and adjust it to your setup.

As a filter

{{ [10, 20, 30] | sum }}

Result (integer)

Function signature

The signature is a technical summary of this template function. It shows the name of the function, the values (called parameters) it accepts, and what type of data each parameter expects (for example, a piece of text or a number).

Function parameters that have a = with a value after them are optional. If you leave them out, the default value shown is used automatically.

Function parameters without a = are usually required. A few optional parameters have no default value, so the signature shows them without a = as well. To check whether a parameter is required, look at the parameter list below the signature. Each parameter is marked as Required or Optional.

The most common optional parameter without a default value is default. The default parameter sets the value a function returns when the function can’t produce a result, for example, when float gets text that isn’t a number. If you leave out default, there is no fallback value, so most functions raise an error and the template fails. The parameter list of each function says what happens. If you set default, the function returns your value instead.

How to read a signature

Here is the signature of the round filter as an example:

round(
    value: Any,
    precision: int = 0,
    method: str = "common",
    default: Any,
) -> float | int | Any

round is the name of the function.
Between the parentheses are the parameters. Each parameter has a name, followed by a colon and the type of value the parameter expects. The type only tells you what kind of value to pass. For default: Any, you pass a value of any type, such as 0 or "unknown", not the word Any.
= 0 and = "common" are default values. You can leave out precision and method, and round uses these default values.
default has no =, but the parameter list marks default as optional. If you leave out default and round gets a value that isn’t a number, round raises an error.
-> shows the type of value the function returns.
Inside a signature, | means “or”. This function returns a decimal number, a whole number, or the value you passed as default.

round is a filter, so the first parameter, value, is the value before the |. For example, {{ 3.14159 | round(2) }} returns 3.14.

The types you’ll see most often:

str: text, such as "hello"
int: a whole number, such as 5
float: a decimal number, such as 3.14
bool: true or false
list: a list of values, such as [1, 2, 3]. list[str] is a list of texts.
dict: a set of keys and values, such as {"name": "Kitchen"}
datetime and timedelta: a date and time, and a duration. For details, refer to Dates and times.
None: no value
Any: any type of value

Some signatures use special forms:

*args means you can pass any number of values, separated by commas. For example, average(1, 2, 3).
value | name(...) means the function is a filter. The value before the | is passed to the filter as its first parameter. Some filter signatures, like the round example, show this value as the first parameter between the parentheses instead.

sum(
    value: list,
    attribute: str | None = None,
    start: int | float = 0,
) -> int | float

Function parameters

The following parameters can be provided to this filter.

value list Required

The list of values to sum. Items should be numeric.

attribute string (Optional)

If provided, this attribute is extracted from each item and summed. Useful for summing a property from a list of objects without needing a separate map call.

start float (Optional, default: 0)

A starting value for the sum. Defaults to 0.

Good to know

An empty list returns 0 (or the start value if you provided one) rather than raising an error.
Every item in the list needs to be numeric. If states or attributes might be strings, pipe them through map("float") or map("int") first.

Sum with attribute

Instead of using map(attribute=...) followed by sum, you can pass the attribute name directly to sum.

Template

{% set items = [{"name": "a", "value": 10}, {"name": "b", "value": 20}] %}
{{ items | sum(attribute="value") }}

Result (integer)

Sum with a start value

Use the start parameter to add an offset to the total.

Template

{{ [10, 20, 30] | sum(start=100) }}

Result (integer)

Try it yourself

Ready to test this? Open Settings > Tools > Template, paste the example into the Template editor, and watch the result update on the right. Edit the values to see how the function adapts to your own entitiesAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more].

More examples

Real scenarios where this function comes up in automations and templates. Copy any example and adapt it to your setup.

Total energy consumption across meters

Sum the state values from multiple energy sensors.

Template

{{
  expand("sensor.energy_meters")
  | map(attribute="state")
  | map("float")
  | sum
  | round(2)
}}

Result (float)

47.83

Total brightness of all lights that are on

Sum the brightness attribute across active lights.

Template

{{
  expand("light.home_lights")
  | selectattr("state", "eq", "on")
  | map(attribute="attributes.brightness")
  | sum
}}

Result (integer)

Calculate total daily cost

Multiply each sensor’s consumption by a rate and sum the results.

Template: Total energy cost

{% set rate = 0.25 %}
{{
  expand("sensor.energy_meters")
  | map(attribute="state")
  | map("float")
  | sum
  | multiply(rate)
  | round(2)
}}

Result (float)

11.96

Still stuck?

The Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with your template and expected result, or share on our subreddit /r/homeassistant.

Tip

AI assistants like ChatGPT or Claude can also explain or fix templates when you describe what you want in plain language.

Related template functions

These functions work well alongside this one:

Average (arithmetic mean): average - Calculates the arithmetic mean of a list of values.
Minimum value: min - Returns the smallest value from a list of values.
Maximum value: max - Returns the largest value from a list of values.
Transform list items: map - Applies a filter to each item or extracts an attribute from each item in a list.

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