Lump Sum vs. Dollar-Cost-Average: Which Wins for Your Windfall?
Example: Windfall to deploy: 100000 $ · DCA period (months): 12 · Expected annual market return: 7 % · HYSA rate while cash waits: 4.5 % · Total investment horizon: 20 years
| Lump-sum advantage over DCA | $9,273 |
| Lump-sum invested: future value | $386,968 |
| DCA path: future value | $377,695 |
| Cash earned while waiting (HYSA) | $2,471 |
Worked example
Deploying $100,000 over 12 months at 7% over a 20-year horizon: LSI grows to $386,968. DCA, with HYSA interest at 4.5% offsetting some drag, reaches $367,221. The cost of DCA behavioral insurance: $19,747. That is the price of sleeping better if markets drop right after you invest. Only you can decide if it is worth it.
Frequently asked questions
What does research say about lump sum vs. DCA?
A 2012 Vanguard study found that lump-sum investing outperformed a 12-month DCA strategy in about 67% of rolling historical periods across US, UK, and Australian markets. The average advantage was 2.3% over the DCA period — not enormous, but consistent and real.
When does DCA make sense despite the cost?
DCA is most defensible when: (1) you cannot stomach a 20–30% drop immediately after investing a large sum, (2) you plan to add regularly anyway and windfall DCA matches that rhythm, or (3) you are investing near or in retirement where sequence-of-returns risk matters most.
What should I do with cash sitting in the HYSA during DCA?
Park it in a high-yield savings account or short-term Treasuries. With rates at 4–5%, the cash drag penalty narrows considerably compared to earlier zero-rate environments. The HYSA rate input in this tool captures that offset.
Is DCA the same as systematic investing from a paycheck?
Paycheck-based investing IS DCA — and it is the right approach for ongoing contributions because you never have a lump sum to deploy. The lump-sum-vs-DCA question applies only when you receive a windfall all at once and must decide how fast to put it to work.