A "power surge" is an oversupply of voltage from a power company that can last up to 50 microseconds.
The expensive plant which is a good idea to use is Aspearagus, as you start off with 150 sun. Avoid collecting any sun or it will reach to 200. Keep collecting sun until it reads "175." Before reaching 200, avoid moving your cursor over the sun. It is wise to either power up your Peashooters or other shooting plants. It is also best to power up your Aspearagus because it can knock out zombies quickly. Avoid moving your cursor over the sun until you receive Power Surge after destroying the last zombie.