We present the results of GENE gyrokinetic calculations based on a series of JET-ILW type I ELMy H-mode discharges operating with similar experimental inputsbut at different levels of power and gas fuelling. We show that turbulence due to slab electron-temperature-gradient modes (sETGs) produces a significant amount of heat flux in four JET-ILW discharges, and, when combined with Neoclassical simulations, is able to reproduce the experimental heat flux for
the two low gas pulses. The simulations plausibly reproduce the high-gas heat fluxes as well, although power balance analysis is complicated by short ELM cycles. By independently varying the normalised temperature gradients (ω T e ) and normalised density gradients (ω n e ) around their experimental values, we demonstrate that it is the ratio of these two quantities η e = ω T e /ω n e that determines the location of the peak in the sETG growth rate and heat flux spectra. However, only increases in ω T e produce appreciable increases in the sETG growth rates, as well as the largest increases in turbulent heat flux. The heat flux increases rapidly as ω T e increases above the experimental point, suggesting that sETGs limit the temperature gradient in these pulses. Multiple sETG eigenmodes with varying parallel wavenumbers are present linearly, and similar structures are found in nonlinear simulations which contribute significantly to the heat flux. Of these structures, modes with increased parallel wavenumber become more prevalent as ω T e is increased, enhancing turbulent transport and contributing to increased profile stiffness.