How to model battery and inverter end-of-life (EOL) and replacement costs

OpenSolar now supports expanded end-of-life (EOL) modelling options for batteries and inverters. This includes the ability to automatically replace equipment once it reaches end of life and incorporate replacement costs into your long-term financial forecasts.

These enhancements allow you to define what happens when:

• An inverter reaches the end of its warranty period

• A battery reaches the end of its warranty period

• A battery reaches its maximum warranted cycle count (total discharge in kWh)

When replacement is enabled, OpenSolar applies the selected replacement cost method and adjusts the cost using your project’s inflation assumptions.

Replacement Cost Options

When configuring replacement for a battery or inverter, you can choose from the following cost methods. All costs are entered in today’s dollars (pre-inflation) and then adjusted using your project’s inflation settings at the time the replacement occurs.

1. Component Cost (Pre-Inflation)

Use the hardware cost already stored in OpenSolar for that component (in today’s dollars).
OpenSolar will:

• Apply your configured inflation rate

• Calculate the inflated cost at the time of replacement

• Include that cost in the project’s financial model

This option is useful when your hardware pricing is already maintained within OpenSolar.

2. Manual Cost (Pre-Inflation)

Enter a fixed replacement cost in today’s dollars.
OpenSolar will:

• Apply inflation to that amount

• Insert the inflated replacement cost into the financial forecast in the replacement year

This option is useful if you want a custom flat replacement cost that differs from the system hardware pricing.

3. Cost per kW / kWh (Pre-Inflation)

Set a replacement cost based on:

• $/kW (typically for inverters), or

• $/kWh (typically for batteries)

OpenSolar will:

• Multiply the rate by the system size

• Apply inflation

• Include the resulting inflated amount in the replacement year

This option is useful when you expect future pricing to scale with system capacity.

Inflation Settings

You can modify the inflation rate used in your financial assumptions. This can be done from the control > design and hardware > setbacks and design settings. From there, edit your template and expand the simulation settings to find the inflation information. 

• Positive inflation increases future replacement costs.

• Negative inflation can be applied if you expect hardware costs (such as batteries) to decrease over time.

This gives flexibility to reflect realistic market expectations in your modelling.

How End-of-Life Is Determined

EOL modelling differs slightly between inverters and batteries.

Inverter End-of-Life Modelling

An inverter is considered to have reached end of life once its warranty period expires.

At that point:

• The inverter is removed from the project simulation.

• If replacement is enabled, a new inverter is added and the replacement cost is applied.

• If replacement is not enabled, the specific inverter component is removed from modelling.

• Standard inverter losses continue to be applied to the project going forward.

This ensures production modelling reflects the absence or replacement of the inverter after warranty expiry.

Battery End-of-Life Modelling

Batteries can reach end of life based on:

• Total discharge cycle count (kWh throughput)

• Warranty period (years)

• Whichever occurs first

Once EOL is reached, the battery is removed from the project simulation unless replacement is enabled.

There are three available EOL scenarios:

1. Cycle Count (Default)

Batteries are typically warrantied to a total energy throughput (total discharge in kWh).

OpenSolar:

• Models the battery’s expected usage over time

• Tracks cumulative discharge

• Marks the battery as EOL once the warranted throughput is reached

This is the current default modelling method.

2. Warranty Years

Similar to inverter modelling:

• The battery is considered EOL once the warranty period (in years) has passed

• The battery is removed from the simulation at that time unless replacement is enabled

3. Lower of the Two

The battery reaches EOL at whichever occurs first:

• Maximum warranted cycle count, or

• Warranty period (years)

This provides a more conservative modelling approach.

Updating Your Default EOL Modelling Settings:

Follow these steps to configure your hardware end-of-life defaults:

Step 1

Navigate to Setback & Design Settings, then open Simulation Settings.

Step 2

Locate the Hardware End of Life Modelling section.

Step 3

Select your preferred Battery EOL simulation method.

Step 4

Configure your Battery Replacement Modelling settings and choose your preferred Cost Method.

Repeat the same steps for your Inverter settings.

If you need assistance, hover over the tooltips within OpenSolar. Each option includes guidance explaining how it impacts system simulation and financial modelling.