Big house, big bills, and the system that actually matches

By Oliver Hill

Where the power actually goes

Large family homes through Caroline Springs, Hillside and Taylors Hill tend to have three things in common that smaller houses do not: climate control that reaches the whole house, more people home at different hours, and often a pool. Those are what decide the system, not the floor area.

Before you get quoted, it is worth knowing which of the three applies to you, because they pull in different directions.

Ducted heating and cooling

Ducted systems are common in this kind of housing, and they are often among the largest loads in the house. The useful part is when they run. Cooling tends to run hardest on hot afternoons, which is when a solar array is producing most, so a lot of that consumption can be covered directly rather than bought.

Heating is less obliging. It tends to run hardest early morning and evening, on the shoulders of the solar day, and in winter when production is lowest. If your ducted system is your main heating, expect more of that load to fall outside your generation than the cooling side does. That is not an argument against solar. It is an argument for being honest about which months the system carries you and which it does not.

A pool is a large load, and an unusually flexible one

A pool pump is a real load, but it is one of the few big ones you can move. Run it in the middle of the day and most of it comes off your own roof. Run it overnight on a timer nobody has looked at since installation and you buy every unit at full price.

If you have a pool, check when the pump currently runs before you do anything else. Shifting it costs nothing and changes the value of the solar you are about to buy.

Two storeys changes the job, not just the view

Double-storey homes are common across these estates. Working at that height means more equipment and more time, and it can legitimately cost more to install the same system than it would on a single-storey house. That is a real line on a quote rather than padding, and it is worth asking an installer to separate it out so you can see it.

A big roof is not always a big array

This is the part that surprises people. Large project homes often have multiple hips and valleys, and the total roof area gets cut into faces pointing in different directions. Each face has to hold a run of panels, so a roof that looks generous can offer less continuous usable space than a plain older roof half its size. Garages, where they are part of the main roofline, sometimes add the most straightforward space on the property.

Mature estate landscaping can add to it. Trees planted when these estates were built are in some cases now big enough to shade part of a roof at some point in the day.

If you want to think about this properly before an installer visits, how much of a roof is actually usable goes through what usable area actually means.

When 10kW or 13kW starts to make sense

Bigger systems become reasonable when there is enough daytime consumption to absorb the extra generation. A household with ducted cooling, a pool and someone home during the day is a genuinely different proposition to one that is empty until six. In the first case the extra panels displace power you were buying. In the second they mostly export, and with Victorian feed-in rates where they are, exported power is worth a fraction of what you avoid paying.

Which system size suits which household works through which tier suits which household, and what a 10kW system costs in Victoria has the prices. The short version: let the consumption decide, not the roof.

If an EV is coming

An electric car adds a substantial load, and in the outer west it adds more than it would closer to town because the driving distances are longer. If you expect one in the next year or so, size for it now. A second visit to add panels costs more than including them the first time, and the roof space you want may not still be there once the first array is laid out.

Solar and an electric car in Victoria covers what it does to consumption.

What this means for a battery

Large households are often good battery candidates, but not automatically. What matters is whether the evening load is big enough to justify storing power rather than using it as it is made. A house with ducted heating running at night and people home has that shape. A house where the biggest loads are the pool pump and daytime cooling may be better served by more panels and a shifted pump timer.

If you are weighing it up, which households actually suit a battery works through the household side, and whether a battery is worth it in Victoria has the costs after rebates.

Homes across Burnside Heights, Fraser Rise and Melton West follow broadly the same pattern, though the newer the estate the smaller the lot tends to be, which changes the roof more than the bills.

Common questions