The established companies in this field, like Abengoa, Bright Source, Sener and Solar Reserve,  all apply the heliostats as big as possible in order to be cost-effective.
The mirror sizes vary from 16-170 m2.
A 100 MW powerplant needs about 1.000.000 m2 of mirrors. So it requires 60.000 to 8.000 heliostats.

According to the concept of Sun2Point, heliostats can be as small as 2.3 × 2.3 m. Due to current mechatronic technologies small heliostats can be installed on site much cheaper per m2 than the large ones. Using small heliostats with the Sun2Point measurement device yields financial profits:

1. -the support frame uses less material per m2 than the large counterparts.
2. -it is possible to assemble the small heliostat manually on site.
3. -the small heliostats are produced in a mass manufacturing plant at a distance from the site.
4. -a small ground anchor fixes the heliostat to the ground.
5. -all calibration is done in the factory.
6. -for starting proper operation only the direction to the tower needs to be supplied.
7. The installed cost will be below 80€/m2.

The heliostat field for a 100 MW powerplant consists of about 193.000 small heliostats. The exact number depends on the expected average DNI and site specific requirements.