SIP or lumpsum: which is better?

A fair comparison starts with the same total amount. Take ₹12 lakh. One investor puts it all in on day one. Another invests ₹10,000 a month for 10 years. If the fund earned exactly the same return every year, the lumpsum would always end ahead, simply because all of the money is invested for the full period. Most of the SIP money arrives later and compounds for less time.

The SIP figures compound monthly and the lumpsum figures yearly, which is how most calculators show them. That convention slightly favours the SIP, so the gap above is, if anything, understated. The last column is the middle path: the full amount is moved in over the first year and then held. It ends close to the lumpsum because the money is fully invested after twelve months.

Real markets do not rise in a straight line. An SIP buys more units when the price is low and fewer when it is high. Over a period with falls, your average cost per unit ends up below the average price over the same months. This is called rupee-cost averaging.

Take a made-up fund whose NAV falls from 100 to 60 and recovers to 100 over 7 months. Investing ₹10,000 each month:

• The average cost per unit is ₹80, below the average NAV of ₹83.
• The SIP of ₹70,000 is worth ₹87,162 at the end, though the NAV only returned to where it started.
• The same ₹70,000 invested at the start would be worth just ₹70,000, because the fund went nowhere overall.

Now reverse the path. In a market that rises steadily, the SIP keeps buying at higher prices and the lumpsum wins. Rupee-cost averaging does not raise expected returns. What it does is reduce timing risk: you never put everything in at a peak, and the result depends less on one entry date. Since markets have tended to rise over long periods, a lumpsum invested early has more often come out ahead, but with a wider range of outcomes, including some painful ones.

An SIP is the better choice when you invest from a monthly salary, when you are new to equity and a sharp fall in the first year would make you stop, or when you want the discipline of an automatic debit.

A lumpsum is the better choice when the money is already in hand, the goal is long term (seven years or more), the fund is a debt or hybrid fund where prices move less, and you can sit through a fall without selling.

A staggered entry suits most large sums. If you receive a bonus, an inheritance or sale proceeds for an equity investment, a systematic transfer plan (STP) is a common approach. You park the money in a liquid or ultra-short fund of the same fund house and transfer a fixed amount into the equity fund every week or month, usually over 6 to 12 months. The money waiting in the liquid fund keeps earning a modest return, and you avoid investing everything at a single price.

• Waiting for a correction. Holding cash until markets fall often means missing gains that are larger than the fall you were waiting for. Pick a plan and follow it.
• Stopping the SIP in a downturn. The months of falling prices are when the SIP buys the most units. Stopping then throws away the main benefit.
• Comparing returns the wrong way. An SIP's absolute return looks lower because much of the money was invested recently. Compare SIPs using XIRR, which accounts for when each instalment went in.
• Running an STP for too long. Spreading a lumpsum over three or four years leaves most of it in a low-return fund and loses most of the advantage of investing early.

1. If you invest from monthly income, start an SIP dated just after your salary credit. That settles it.
2. If you have a lumpsum for a goal less than three years away, keep it out of equity altogether.
3. If the goal is long term and you are comfortable with volatility, invest it at once or use an STP over 6 to 12 months.
4. Check each STP transfer and SIP debit for exit loads or tax on the switch from the liquid fund.
5. Measure the result with the fund's XIRR rather than its absolute return.