A thermal inkjet printhead with generally planar heater elements disposed in respective bubble forming chambers, whereby the area of each heater is less than 300 μm2. The heater area influences the energy required to heat the heater volume up to the fluid superheat limit; the energy required to heat the protective coatings covering the heater to the superheat limit; the heat that diffuses into the underlayer prior to bubble nucleation; and, the heat that diffuses into the ink prior to bubble nucleation. Reducing the surface area of the heater reduces all of these terms and has a significant impact on the energy required to form a bubble and eject ink.