The secret way to reduce your electricity bills using aircon and solar

No-one likes to come home to a house that feels like a sauna, especially if they have air-conditioning installed. And the same is true for freezing in winter. But electricity prices have risen so high, that even moderate aircon use can have a significant impact on your wallet as well as your emissions, which means many of us are reluctant to turn our aircon on until we are desperate.

There is some good news - if you have solar, you’re in luck. We have a tricky method to dramatically reduce your bills; it’s just a matter of timing, and insulation.

What many people may not know, is that air-conditioners generally have to work hardest in the period immediately after turning on from standby and then they go into more of a temperature maintenance cycle once the desired temperature is reached. This initial period is when you’ll see a huge spike in your energy use, as the aircon has to kick-start from zero, and battles to get the house to the ambient temperature set on the thermostat.

So why not set your aircon to start earlier, when you have free solar energy!

Moderate insulation
If your home is moderately well insulated, use a timer to start up your aircon when you still have solar energy in the afternoon, to do the bulk of the hard work and pre-cool your home a little bit. This is particularly useful if you have west-facing solar panels - making lots of energy in the afternoon. When you return home, you can then bring the temperature down further, but the hard work will already have been done.

Good insulation
If your house is very well insulated, you could run your aircon even earlier on a low power setting throughout the day and simply turn it off when your solar production drops away. Your house might stay cool enough throughout the evening or require only low power to remain at a comfortable temperature.

Poor insulation
But if your house is poorly insulated (e.g. you have cracks in door and window frames, or no ceiling insulation), then pre-cooling might not be helpful as it will be offset by warm air leaking in from outside. In that case, just use the aircon when you’re home and get some quotes for insulation!

Every house will be different, and the exact starting time and power settings may need to change over the course of the season, depending on your solar panel tilt and compass orientation. So experiment with different settings and watch your dashboard for the results.

Let’s look at an example:

BEFORE: This home owner turned the aircon on just after 6pm and their energy use spikes. All energy for the aircon comes from the grid, at an expensive 35c per kWh.

AFTER: The same home owner set the aircon time to come on at 4pm. Their energy use spikes, but they are using only their free solar energy!

Plus, If you are a Solar Analytics customer, you will receive a notification in your dashboard, if we detect that you are using your air-conditioner outside of your solar curve - a great reminder to get that timer working!

Solar Analytics dashboard aircon notification

And of course, on top of timing, you’ll need to cover some basics to ensure that your aircon runs as efficiently as possible. These steps will help all aircon users get more value, whether you have solar or not!

1. Remove all draughts. That means closing doors and windows, of course. But also, check for gaps under doors and use silicon sealant, or draught stoppers.

2. Keep warm electrics away from the aircon thermostat. This includes lights, computers, printers, clothes dryers, and even ovens. (Our kitchen is quite near to the thermostat, so when we are using the oven, we need to keep the door closed between the kitchen and the hallway where the thermostat is located).

3. Change the aircon filter regularly (many manufacturers recommend once a month during Summer). Build-up on the filter makes the aircon hugely less efficient.

4. Close your blinds. This one can be really painful to be diligent about, but the insulation from keeping your blinds and drapes closed really does make a difference to how hard your aircon has to work (and how much energy it uses to keep your home at the right temperature). If you are lucky enough to get sunlight in winter, by all means, keep those blinds open during sunny periods - that will help warm up your home naturally. And then shut up shop to keep the heat inside.

So there you have it. We’d love to hear from you if you think you can implement our energy-saving strategy. It would be great to see your before and after graphs! Learn more about Solar Analytics monitoring and how it can help you reduce your electricity bills.

Solar Analytics
We are Australian Photovoltaic Engineers, Software Developers, Scientists, Solar Technicians and Designers, all passionate about sustainable energy and the power of solar.
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