How much faster can my commute be if I use a power meter? When biking to work, my routes have have stop signs, stop lights, and other interruptions every few blocks or so.

My understanding is that if I reach my power at target heart rate soon after stopping so that I still save glycogen, my commutes would be faster. I'm commuting five days a week. How effective is it really in practice? How much would I expect my average speed to increase?

Update with examples.

After stopping at stop signs, I plan to accelerate by keeping my power around 150W depending on my fitness.

After stopping at traffic lights, I plan to gradually raise my power to 150W because my heart rate would drop.

In both cases, my heart rate shouldn't exceed 180-age. With power, I know that I'm not overshooting it.

Update: Sample morning race to work ride in response to a comment.
With that many interruptions your own performance is unlikely to make much difference to your commute times. Sprinting for the lights, when safe, is much more likely to help. If it's mostly stop signs rather than lights, getting going fast might help but you don't need a power meter to tell you that. For me, leaving a few minutes later in the morning makes much more difference - not only are there more cars going my way and holding me up, but there are more coming the other way on narrow roads so passing the queues becomes harder. Bin day or a badly parked delivery van jump out of a list of timings. 

You don't say anything about the distance and time but I assume you measure it. Have a look at the variability over recent rides, and try changing a few variables - can you even tell the difference between holding back until the fast bits, and going at everything hard?

A power meter is a training tool, and while you can incorporate commutes into a training plan that doesn't sound like what you're doing. Personally I prefer not to have a screen when commuting in case I look at it; I'd rather keep my eyes on the road. But maybe your commutes are in more benign conditions.