Emergency fund yield index
What should an emergency fund earn? $968
Using a $25,000 example, 0.38% APY earns $95 per year while 4.25% earns $1,063.
Bottom line
Emergency fund yield index is worth fixing when the cash is not needed for daily bills.
Keep enough in checking for near-term transactions, then move surplus cash into a liquid, insured account or a deliberate cash ladder.
Next calculation
Taxes can change the high-yield savings vs T-bill winner.
If the cash is taxable and your state income tax rate is meaningful, compare after-tax yields before deciding between HYSA and Treasury bills.