SavingsCELO has a very simple design from the user's perspective:
User can deposit X amount of CELO to receive back Y amount of sCELO tokens.
After some time passes, user can return Y amount of sCELO tokens to redeem >X amount of CELO tokens back.
NOTE: Deposits are instant but redemptions are delayed by the unlocking period (3 days on Mainnet).
While the number of sCELO tokens a user holds doesn't change over time, the value of sCELO vs CELO increases as voter rewards come in. When a user eventually redeems their sCELO for CELO they will receive roughly the same amount of CELO back as if they had staked it on a validator group. sCELO interest accrual mechanism is very similar to how Compound cTokens work.
CELO -> sCELO conversion rate is calculated as:
Current total sCELO supply / Current total CELO deposited in SavingsCELO contract