The battery sizer is a tool in Enerflo that determines and configures battery settings for a design. It generates sizing recommendations and lets reps set the battery's purpose and, for Self Consumption batteries, grid charging behavior.

The battery sizer can be accessed in two ways.

Option 1: From the design stage, click the battery icon on a completed design.

Option 2: Open the design card, open the Modify Design menu, click +Add Battery, then click the Recommendations link to open the battery sizing tool.

The Battery Recommendations section of the battery sizer includes a Purpose dropdown that determines how the battery is expected to be used. Set Purpose to Self Consumption to enable additional options, including grid charging.

Grid charging lets the battery draw power from the grid (utility imports) to supplement solar charging. This is useful in markets with expensive time-of-use rates or demand charges, such as Arizona.

Requirements: Purpose must be set to Self Consumption. The battery must be selected through the battery sizer specifically — grid charging has no effect if the battery is added to the design any other way. It works in both the Optimus proposal and the V2 deal stage. No org-level enablement is required.

To set up grid charging:

To add the battery sizer to your Optimus proposal, you will need to add the battery sizer slide to your default proposal.

Any user with admin permissions can add the slide by clicking Settings > Proposal > Optimus Templates. Click into the template you'd like to add it to, and scroll down to the slide library.

Click the + next to the Battery Sizer slide to add it to your slide deck.

The battery sizing tool's recommendation engine combines three data sources: a full year of hourly usage data (from Genability), hourly production data (from the design or PV Watts), and the specs of each available battery. The rep supplies the remaining input: how the homeowner wants to use the battery.

The left side contains the controls a rep uses to dial in the homeowner's preferences, which drive the battery recommendations. Changes made here are combined and applied together — either by clicking "apply changes" or by selecting a battery — rather than one at a time. These controls are primarily responsible for selecting the energy use the battery needs to be able to handle.

Some of this is done by targeting a specific daily value of energy use (a "worst case" scenario to prepare against), and some of this is by taking that daily usage and paring it down to just what the homeowner wants the battery to cover specifically.

The inputs a rep makes with these controls save to the design (either within the V2 design stage or the Optimus proposal) when they click "apply changes" or select a battery to use.

Summer/Winter: Selects which season's usage data the sizer uses. There is no universally right choice — it depends on when the homeowner expects to need the battery most. For example, a homeowner in a hot climate may choose summer to account for heavy AC usage, while a homeowner with electric heat may choose winter.

Purpose: Sets how the homeowner plans to use their battery. It affects which batteries the recommendation engine suggests, as well as how savings are calculated later on the deal. There are two options:

Backup: The battery is kept on hand for power outages; the homeowner does not plan to use it day-to-day. This does not reduce the homeowner's utility bill after going solar, but provides peace of mind if the grid goes down. Markets prone to weather-related outages tend to see more Backup batteries sold. For Backup, the sizer targets the day (in the selected season) with the worst solar offset, to prepare for a worst-case scenario.

Self Consumption: The battery is charged and discharged daily to reduce the homeowner's day-to-day utility usage and costs (similar to arbitrage; some lenders use the terms interchangeably). Self Consumption aims for batteries that can be charged and discharged each day so the homeowner uses as little grid energy as possible. For Self Consumption, the sizer targets the day (in the selected season) with the average offset, to meet the homeowner's most common needs.

Desired Backup Power: A slider or toggle that sets what percentage of the daily energy use the homeowner wants their battery to cover — in other words, how aggressively the battery should handle their needs. It is fully preferential, but a higher percentage results in a larger, usually more expensive, battery recommendation.

Battery Backup Hours: An hour selector that narrows the daily usage total (set by Purpose and Summer/Winter) down to the specific hours the homeowner wants the battery to cover. Like Desired Backup Power, this is preferential — a wider hour range results in a larger battery. The specific hours chosen also matter, since usage is typically higher in the afternoon than overnight. This setting also affects how the battery's performance is modeled: for Backup, these hours are when an outage is simulated, so homeowners should choose the hours an outage would inconvenience them most; for Self Consumption, these hours are when the battery discharges to avoid grid usage, so matching them to the homeowner's most expensive time-of-use rate hours maximizes savings.

The top row shows the data the sizing tool uses to generate its recommendations, based on the left-side selections:

Daily Energy Use (kWh): The sum of hourly usage for the day selected by the Summer/Winter and Purpose settings. If Desired Backup Power and Battery Backup Hours are both set to their maximum, the recommended battery is sized to this full value.

Recommended Capacity (kWh): The ideal battery capacity for the homeowner, calculated from Daily Energy Use and then reduced based on the Desired Backup Power and Battery Backup Hours settings. Available batteries have their quantities increased (especially for small, stackable batteries) to match this capacity as closely as possible.

Solar System Details: The sum of hourly production for the selected day, plus the offset percentage for that day (production divided by consumption).

Based on the left-side inputs and top-row data, the installer's available batteries are listed below, in order of cost to the homeowner for the recommended quantity. If there are more than three options, an arrow (>) lets the rep navigate to see the rest. Prices include applicable fees and are shown as price-per-watt (ppw), unless the deal is battery-only, in which case ppw is not shown.

For each battery, the rep and homeowner also see the backup hours (how many hours the battery, or batteries, can discharge during the selected hours and percentage), along with the capacity, peak output power, and warranty years from the battery's specs (adjusted for quantity where applicable).

Quantities are increased automatically as needed to meet the Recommended Capacity, but reps can manually increase or decrease the quantity based on homeowner preference. Once satisfied, the rep selects the battery to add it to the deal.