National Grid (LSE:NG.) shares have been on quite a rollercoaster ride over the last five years. Yet despite constantly swinging up and down, the energy infrastructure enterprise has seen its market-cap trend upwards. And with dividends still flowing into the pockets of shareholders every year, investors have reaped positive returns.

Combining the 23% share price gains since July 2020 with ongoing dividend payments means that a £1,000 initial investment’s now worth around £1,300. That roughly works out to a 5.4% annualised gain, which is hardly groundbreaking. But for conservative investors looking to protect their wealth rather than grow it, National Grid’s proven to be a good parking spot for capital so far, staying largely ahead of inflation.

Of course, the question now is, can it continue to deliver similarly robust returns moving forward?

Looking to the future

The firm has begun executing an ambitious five-year infrastructure upgrade plan, with £9.8bn already spent in its 2025 fiscal year (ending in March). This expansion of assets, paired with favourable US regulatory shifts and flat controllable costs, resulted in underlying profit growth exceeding analyst expectations.

At the same time, successful capital raises, while dilutive for shareholders, have allowed the company to kick-start its debt reduction programme. Needless to say, this is all pretty positive news. And if it’s a sign of what’s to come as the firm progresses with its new strategy, the current upward trajectory of National Grid shares could start to accelerate. At least, that’s what the current analyst forecasts are suggesting.

While there’s a range of opinions, the average consensus projection for the National Grid share price is that it could reach 1,192p by this time next year. That represents a potential 15% gain in just the next 12 months. And with dividends expected to continue, there’s an extra 4.5% yield on the table as well. In other words, that initial £1,000 investment could soon be worth closer to £1,554.

Taking a step back

As encouraging as this outlook seems, there are some critical risks to carefully consider. And arguably the most prominent is execution risk.

In total, National Grid intends to invest £60bn by March 2029. Executing projects on this scale is notoriously challenging and susceptible to delays, cost overruns, and mismanagement. And with shareholders likely to be diluted even further in the future, National Grid shares could be kept on a short leash if it can’t continue to hit planned milestones.

Delays aren’t just problematic in terms of potential share price volatility but also debt burdens as well. A big driver of executing this plan is to deliver a rebound in free cash flow generation, as modern energy infrastructure is more efficient. But if those benefits fail to materialise, management’s ability to continue paying off its debts while growing dividends could come into question.

Put simply, despite being a FTSE 100 stalwart, National Grid’s carrying notable risk at the moment. And investors will need to consider these factors carefully before adding it to their investment portfolios.