If a battery adder appears as a negative amount on TPO (lease/PPA) proposals but a positive value on cash proposals, this is because battery adder pricing calculations interact differently with TPO vs. cash pricing logic. It is not caused by a misconfiguration in the adder's pricing settings.
On a TPO deal, the finance company pays out based on a fixed rate per watt for a 'standard' install. That rate is baked into their underwriting model and doesn't change deal to deal — it's not tied to what a specific project actually costs to build.
Adders exist because some projects cost more than standard: a main panel upgrade, extra roof planes, critter guard, tree trimming, whatever the site requires. None of that is reflected in the finance partner's flat per-watt rate.
So here's the math in practice as an example. If the TPO payout on a project is $10,000, and the project needs a $1,200 MPU adder, the model deducts the adder cost from the payout ($10,000 - $1,200 = $8,800). Now, the payout reflects the real net economics of that specific project rather than a flat number that ignores what it actually took to build.