The average Stocks and Shares ISA for people aged 45 to 54 is estimated to be £25,362.

But how much could it be worth over the next decade? To calculate this, we would have to make the following assumptions:

• Initial investment: £25,362
• Average annual return: 8%
• Investment period: 10 years
• No additional contributions
• Dividends reinvested
• No taxes payable on ISA wrapper

Please note that tax treatment depends on each client’s individual situation and may change in the future. The content of this article is for informational purposes only. It is not intended to be and does not constitute any form of tax advice. Readers are responsible for conducting their own due diligence and obtaining professional advice before making any investment decisions.

I calculate that on a compound growth basis the portfolio could grow to around £54,754. This is more than double the original amount.

Of course, future profits are never guaranteed. Markets move up and down, especially in the tiny term. That said, history shows that patient investors who continue to invest in high-quality companies should benefit from long-term stock market growth.

But which quality companies can facilitate generate these returns?

Can the National Power Grid still be an attractive investment?

One stock that many income-oriented investors continue to watch is National Network (LSE:NG.). The company operates critical electricity and gas infrastructure across the UK. Because these assets are vital to everyday life, revenues are typically more predictable than for cyclical businesses.

National Grid has long been popular with dividend investors due to its history of shareholder payouts and defensive nature. It currently offers a dividend yield of 4.1% with a forecast dividend growth of 2.4%.

Looking ahead, the ongoing shift towards electrification, renewable energy projects and grid modernization could also create opportunities for future growth.

Please remember that we operate in a highly regulated industry where rules are subject to change. Together with higher interest rates, this could impact future earnings and shareholder returns.

In my opinion, the biggest attraction is the combination of steady cash flow and reliable dividend income. While it’s unlikely to deliver explosive growth like some AI tech stocks, investors looking for reliability may find this business model attractive.

Is it time to consider a larger Stocks and Shares ISA?

An ISA offers tax-efficient growth, flexibility and the ability to build wealth without capital gains or dividend tax liabilities. Even relatively modest sums can potentially grow to surprisingly gigantic amounts over a decade or more.

The numbers become even more attractive if fresh cash is deposited during the working years. For example, assume that the above investor makes one change to the assumptions listed. This time they are adding and investing an extra £3,000 a year.

I calculate that after 10 years the investor could have a total pot worth around £98,213.

I think investors may be underestimating how powerful the effects of modest investments combined with the magic of compounding can be. Patience and regular contributions can significantly strengthen your retirement finances.

In addition to companies like National Grid, owning a range of quality growth stocks can significantly boost your portfolio’s annual returns. For example, Alphabet (NASDAQ:GOOGL) i Apple (NASDAQ:AAPL) have returned 26% and 29% per year, respectively, over the last decade.

All things considered, I don’t think the real question is whether a Stocks and Shares ISA can facilitate you build wealth. It’s about whether investors are making the most of the years leading up to retirement. And if not, what opportunities might they be missing today?

Should you invest £5,000 in National Grid Plc now?

If investing expert Mark Rogers and his team have stock advice, it can pay to listen. After all, Twelfth Magpie’s flagship Share Advisor newsletter, which it has run for almost a decade, provides thousands of paying members with the best share recommendations from across the UK and US markets.

Mark believes there are 6 standout stocks that investors should consider buying right now. Want to check if National Grid Plc is on the list?

Harshil Patel owns shares in Apple and Alphabet.