Do it at the same time. I would also recommend you switch of your gyser when everyone has used hot water. unplug the anything u a are not using. Switch off the lights in rooms you are not in. Have you thought of using solar power. It is way cheap and you can slash your electricity bills by 89% or even eliminate it completely. Our electricity used to be cut because we couldn't afford to pay the electricity bill sometimes, now we use solar power and man, are we glad we changed it. Yo can do it yourself to avoid paying thousands of dollars. Believe me you can do it way cheaper. read my report and see for yourself. Everyone avoids solar panels but they really save you money in the long run. It is an investment you have to think about. In the end you wont worry about high electricity bills. Believe me!!!
Install solar panels yourself :
or click my profile to read more and find links and then decide. You will be shocked how cheap it is to Do It Yourself