With household bills still feeling painfully high and inflation continuing to squeeze disposable income, I think many investors are asking whether an ISA could one day cover a major cost like energy bills.
According to EDF Energy, the average UK household currently pays around £137 a month under the latest Ofgem price cap. That works out at more than £1,600 a year — a meaningful expense for most households. So how big would an ISA need to be to cover that for life?
Crunching the numbers
To keep things simple, an investor is assumed to want to cover a £1,644 annual energy bill using income from an ISA invested in a broadly diversified portfolio.
A commonly used rule of thumb is that around 4% of a portfolio can be withdrawn each year without running it down too quickly over the long term. It’s not perfect, but it provides a useful starting point.
On that basis, an ISA would need to be worth £41,100.
Put another way, this isn’t about building a life-changing fortune. It’s about building a relatively modest pot that could potentially cover a very real and recurring household cost.
Of course, markets won’t move in straight lines and returns will vary year to year. But it does suggest the gap between having nothing and an income stream that covers a key bill may not be as wide as it first appears.
Index tracker
One simple way to approach this would be using a low-cost FTSE 100 ETF inside an ISA, such as the iShares Core FTSE 100 UCITS ETF, (LSE:ISF), which tracks the UK’s largest companies in a single, diversified investment.
At the time of writing, it offers a trailing 12-month yield of 2.9%. Based on that yield, an investor would need a significantly larger ISA pot to generate £1,644 a year in income.
But there is another route — picking individual dividend-paying stocks. This approach does require more effort and research, and it comes with less diversification. However, in return, it can offer the potential for a higher income stream than a broad market tracker.
Stock pick
Aviva (LSE:AV.) offers a forward dividend yield of 6.6%, which immediately puts it in the higher-income bracket of the FTSE 100. The key question for investors is whether that level of income is sustainable.
The good news is that the dividend is not being driven by a single, fragile source. Aviva has been steadily reshaping its business model towards more capital-light areas such as wealth, retirement, and fee-based insurance services.
That shift matters. It means the dividend is increasingly supported by recurring earnings rather than cyclical insurance profits, which should make it more resilient over time.
Recent performance also suggests momentum is building across the group, with management already delivering on medium-term targets ahead of schedule.
That said, risks remain. Insurance results can still be affected by claims inflation, while investment returns remain sensitive to bond markets and broader economic conditions.
Overall, I think the stock’s yield looks well supported by a more diversified and resilient earnings base. If management continues to execute at this pace, it could become exactly the kind of income-generating stock that helps an ISA cover rising costs like energy bills faster than many investors expect.
