> For the complete documentation index, see [llms.txt](https://docs.betterbuilding.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.betterbuilding.io/user-guide/workflows/energy-efficiency/advanced-hvac/customise-fan-performance-curves.md).
# Customise fan performance curves
The EnergyPlus Fan performance curve is a table that describes how electric power consumption varies with air flow rate. For more details, we recommend reviewing the [EnergyPlus documentation](https://bigladdersoftware.com/epx/docs/22-2/input-output-reference/group-fans.html#fanvariablevolume). The observable effect of a custom fan performance curve will be in the annual energy consumption for the air-conditioning fans.
Advanced HVAC allows for custom fan performance curves to be modelled on all HVAC fans. In this example, we model a typical static pressure reset fan curve on an Air Handling Unit fan, per the following coefficients.
$$
P
fan
\=0.0012−0.0579⋅PLR
fan
+0.5864⋅PLR
fan
2
+0.41712⋅PLR
fan
3
$$
{% hint style="success" %}
Customise fan performance curves on an Air Handling Unit fan by selecting a ‘Air Handling Unit’, then the 'Supply Air Fan', and then 'Customise Curves'. Next, select 'Electric Power Function of Flow Fraction' and 'Quartic Curve'. Lastly, enter the coefficients of the fan performance curve. Hit 'Update, then 'Save'.
{% endhint %}
---
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