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.

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

60

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 default are required.

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

Function parameters

The following parameters can be provided to this filter.

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.

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

30

Sum with a start value

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

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

160

Try it yourself

Ready to test this? Open Developer 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.

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

47.83

Total brightness of all lights that are on

Sum the brightness attribute across active lights.

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

447

Calculate total daily cost

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

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

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.

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.