With its cars famed for rapid acceleration, it may be no surprise that the same can sometimes be true of the Tesla (NASDQ: TSLA) share price. Tesla stock is up 71% in the past year (in fact, it has jumped almost that much in the past couple of months alone).

The long-term record is even more impressive.

One thousand pounds invested five years ago would have bought Tesla stock now worth almost £13,000 (excluding currency movements during that period).

That is an incredible record.

But, with the company reporting its first ever fall in annual car sales last year and a number of risks looming large, could the best days of Tesla stock now be in the rearview mirror?

Reasons to be fearful

I see quite a few elements of the current Tesla investment case that concern me.

For beginners, that decline in annual sales.

To keep things in perspective, it was small (around 1%) and comes after years of strong growth at the carmaker. Still, it could be an indication that some long-term risks are now coming home to roost.

One that concerns me as a potential Tesla investor is the sheer number of companies now making and selling electric vehicles at volume.

Tesla was once the clear leader in this space if ignoring long-established companies like Toyota. But a host of other companies have been closing in fast. Indeed, last year Chinese electric vehicle maker BYD sold more than double the number of cars Tesla did.

Such competition leads to downward pricing pressure, meaning profit margins in the industry could be squeezed.

A lot of rivals are loss-making but Tesla has been profitable in recent years. With growing competition, though, that could change.

Another risk is possible reduction or elimination of tax credits in key markets like the US. That could further hurt demand.

Tesla is here for the long term

However, it is important to bear a few things in mind.

Tesla remains a key player (arguably the key player) in its space. Its brand is strong and it has a large installed user base. Its ability to innovate continues to help set it apart from many rivals and gives it pricing power.

The company is well-established, selling tens of thousands of vehicles each week even before it taps markets like driverless taxis. It is also profitable.

On top of that, vehicles are not the only game in town. Energy storage is a large and growing business for the company.

In the most recent quarter, energy storage deployments were 31.4 GWh. The company is making impressive progress on its ambitious long-term target of producing 1 TWh of energy storage per year.

The current valuation looks high to me

On balance, then, I see a lot to like here even considering the risks.

But Tesla stock trades on a price-to-earnings ratio of 113. Allowing for its growth prospects, that still strikes me as unreasonably high — and far beyond what I would be willing to pay.

So while Tesla’s best days may yet be ahead of it – and ultimately its future valuation could justifiably be higher than it is today —  I reckon the stock price has got far ahead of itself for now.

I have no plans to buy.