Are 7.2KW hob and 3KW oven should be on separate circuits?

Usually the oven and the hob are combined in the UK. If the oven and hob are built into a single unit, it might not be feasible to put them on separate circuits. In such cases, the combined load would need to be considered.

Not necessarily. Both appliances can share a 32A circuit wired in 6mm2 cable. You could put both their own circuits for convenience of maintenance or in the event of one developing a fault, but personally I always share the circuit. Technical guidance states up to 15kW total load can be managed on a standard cooker circuit.

The main issue is what does the manufacturer say. Normally a 3kw oven needs a separate 20a Circuit because a 3kw load on a 13a socket can over time overload the socket leading to an electrical fire. Most ovens are 2.2kw to 2.5kw. Self cleaning ovens use lots of power to clean themselves hence the 3kW rating.

I would always run separate circuits for these. There’s not to say you can’t or anything inherently bad about using same circuit but for me better dividing the circuits. If the circuit ever develops an issue you’d lose both cooker and hob. Microwave dinners it is!! Plus putting both on the same circuit you’re looking at 45A protective device and cables anything north of 10mm depending how it’s installed. Can be a pain to second fix at times..particularly if the client wants the isolator hidden in the back of a cupboard.

Yes separate, I always put hobs and ovens on separate circuits as hobs are bigger loads than ovens because of this they’ll have different cable sizes. It also beneficial to have them separate because if they are on one circuit and one of them is faulty and trips the protective device than you are without both hob and oven.