Gas is sold in megajoules (MJ) and electricity in kilowatt-hours (kWh). The running cost is simply usage × tariff. What makes the comparison tricky is that electric appliances — especially heat pumps — extract more usable heat per unit of energy than gas appliances.
A heat pump hot water system uses a refrigerant cycle to move heat from the air into the water. It delivers roughly 3 units of heat for every 1 unit of electricity consumed — a coefficient of performance (COP) of ~3. The 2.5 kWh/day default already reflects this real-world COP, compared to the 18 MJ/day a gas storage heater consumes.
Reverse-cycle A/C (split system or ducted) works the same way for heating. A typical system achieves a COP of 3.5–5 in mild conditions — dramatically outperforming gas heating, which loses 15–20% of its energy up the flue. The 15 kWh/day default reflects a medium-sized ducted system for a 4-bedroom home running on a cool day.
For cooking, the efficiency gap is smaller. Gas hobs are around 40–55% efficient (much of the heat escapes around the pot); induction is 85–90% efficient. The 3 MJ/meal vs 0.4 kWh/meal defaults already reflect these efficiencies.