The electrification of public transport has the potential to mitigate greenhouse gas emissions and support the electricity system, but this potential remains dependent on intra-day charging strategies. Our paper explores – using the metropolitan Melbourne bus network as an example – the trade-offs between least-cost tariff-based fleet charging against charging strategies that either minimise greenhouse gas emissions or wholesale prices. We use a counterfactual analysis across 5 years of historical (2017-2021) and 5 years of modelled (2022-2026) changes to wholesale electricity prices and emission intensities in Australia’s National Electricity Market. We find that current tariff structures with high daytime volumetric usage and demand charges mute climate and wholesale market signals. Across the years of 2017-2026, fleet charging strategies that minimise greenhouse gas emissions average further indirect emission reductions of 33.4% but incur a 103% increase in annual electricity bills. Optimising for wholesale market price signals results in an average 69% increase in bills across the same years. However as low wholesale market prices increasingly coincide with lower grid emission intensities, optimising for wholesale market price signals also leads to further indirect emission reductions that average 25.2% between 2021-2026. Given expectations of widespread electric vehicle adoption, these findings necessitate an urgent tariff reform to allow relevant wholesale price signals to pass through to electric vehicle owners.