I'm with your hubby I'm afraid. Double glazing is mostly a way to deal with cold radiating into a house, and heat leaking out of the house via conduction which is not the problem in Perth. Sure it will prevent heat from radiating into the house via the windows but mostly that's not how houses heat up in Australia. What causes a house to heat up is sunlight warming up the ambient air inside the house via a greenhouse effect which double glazing will not prevent, or hot air being born into the house on the wind. So double glazing will only prevent this if you intend to shut the house up all day. In which cause it's just the lack of air movement not the insulative properties of double glazing doing that. Single glazing would also do that.

In Australia what matters most is cross ventilation in order to create a restful environment. Evaporative cooling works effectively when you have good cross ventilation as it's the evaporation of the water vapour causing the cooling effect. Additionally you do not want to shut up a house with evaporative cooling as you'll get condensation and mould inside the house.

So if you are 100% on double glazing it will only be effective with refrigerated air conditioning as it's relying on preventing air exchange between the inside and outside of the house to work and preventing conduction of ambient air temps. Double glazing is not popular here for a reason, it's the wrong solution for our climate.

Cross ventilation and proper solar management is the correct solution for our climate. So I'm with your hubby I think it's wasted money that would be better spent on controlling the direct sunlight to the home and proper ventilation.

I'm with you, black bamboo. If your windows are shaded from the summer sun, that is enough. No need for double glazing. And let's face it, in Perth, a blanket for a couple of days in winter, is a better financial alternative. In the house you had before, if it was not orientated correctly for stopping the summer sun, or not letting the winter sun in, then yes your power bills will be high, because your home was not built facing the right way.
But with this home you can make the sun work for you in winter, and stop it in summer.
Still have refrigerated air conditioning, but only use it when really required. Maybe install solar panels to cover your air con use cost, and the pool cost.

wowsers. Ahhhh so much insight and knowledge that you both have. I am really confused now. Could I sway either of you to listen to this podcast and give me your critical opinion?

https://undercoverarchitect.com/podcast-choosing-energy-efficient-glass-windows-and-doors/

I am in Brisbane and a further north town . Except for three months of the year my doors and windows are open , particularly on the North and East where most of the cooling breezes come from . Having a counter door or window on the South and West really increases the flow . I have a tint on all the Western and Southern windows in Bris and verandah in the town .I find that this ,with ceiling fans ,are usually all that I need . I do have reverse cycle which is only used for a few days in summer and winter . Curtains and blinds are made with blockout linings . We did have double glazing Northern windows on the apartment in the town because of the pub nightclub noise until 3am on weekends . I cannot see the point in a warm climate where you want windows open . Cold areas - yes , + fireplaces .There are plenty of external awnings available to cut the heat .