UK Pound-Cost Averaging (2026/27): Lump Sum or Drip-Feed?

Q What is pound-cost averaging?

Investing a fixed amount at regular intervals, typically monthly, instead of investing a lump sum at once. Because the amount is fixed, it buys more units when prices are low and fewer when they are high. It is called dollar-cost averaging in the US. Anyone paying a set amount into an ISA or pension each month from their salary is already pound-cost averaging.

Q Does pound-cost averaging beat lump-sum investing?

On average, no. Vanguard's February 2023 paper compared investing a lump sum at once with splitting it into three equal parts invested a month apart, measuring wealth one year later. Using the MSCI World index for 1976 to 2022, the lump sum came out ahead 68% of the time; for the UK, using the FTSE All-Share for 1986 to 2022, 68.1% of the time. The paper links this to shares and bonds having outperformed cash over most of the period, so money invested earlier usually had longer to earn that extra return. Cost averaging did better in periods when prices fell soon after the start.

Q So why do people still drip-feed?

Mainly behaviour. Vanguard's paper suggests cost averaging might be considered by investors with a very high aversion to risk and losses who would otherwise be tempted to keep a lump sum entirely in cash - and on its figures, cost averaging beat staying in cash 69% of the time. Spreading the entry can make a large fall straight after investing easier to live with, which can stop someone selling at the bottom. And if you are saving from salary, there is no lump sum to invest anyway.

Q When should I use a lump sum rather than drip-feeding?

If you have a long horizon and could sit through a sharp fall without selling, the evidence favours investing the lump sum. Easing in may suit you if a large immediate paper loss would cause you to abandon the plan, or if you are moving savings from cash into shares for the first time. Either way, check the money is not needed in the short term, and remember the £20,000 annual ISA allowance limits how much you can shelter from tax in one year.

Q How long should a drip-feed period be?

Vanguard found that the longer the averaging period, the more of the expected return is given up while money sits in cash: in its simulations of a $100,000 investment, the median shortfall against a lump sum was $504 for a three-month split and $1,491 for a six-month split. If you do ease in, a short period gives up less. For regular monthly saving from income, the question does not arise - you invest each contribution when you have it.

Q Does drip-feeding work for funds and ETFs?

Yes, but check the costs. With funds, regular contributions usually buy units at the next daily price. ETFs trade on an exchange; some platforms offer free or low-cost regular investing into them while others charge a dealing fee per trade, which can be expensive relative to a small monthly amount. Compare the platform's regular-investing and dealing charges before choosing.

Q Should I try to "buy the dip"?

Waiting for a fall is a form of market timing, which is hard to do consistently, and money held back in cash while you wait gives up return in the same way as a long averaging period. A simpler approach is to keep regular contributions going whatever the market is doing, and if you have extra money to invest, invest it when you have it rather than holding it back for a better entry point that may not come.

Q Does averaging apply to retirement saving?

Yes - regular workplace pension and personal pension contributions are averaging into the market throughout your working life. Near and in retirement the problem reverses: withdrawals from a falling portfolio can do lasting damage (sequence-of-returns risk). Some retirees hold a cash reserve so they are not forced to sell after a fall, and some pension funds are designed to move gradually from shares towards bonds and cash as retirement approaches ("lifestyling"). Check what your own fund does - many funds keep a fixed mix whatever your age.