Why solar and air conditioning suit each other

An air conditioner is at its most useful on a hot, sunny afternoon, which is when rooftop solar panels produce the most electricity. Power you make on your own roof and use straight away is power you do not buy from the grid, so the more of your cooling you run in daylight, the less you pay for.The same holds in winter. A reverse cycle air conditioner heats as well as cools, and a clear winter day still gives the panels a few good hours around the middle of the day. Heating the house then, on your own power, costs less than heating it after dark on grid power.

How a heat pump makes electricity go further

Most home air conditioners are heat pumps, and most are reverse cycle, so they both heat and cool. A heat pump does not make heat the way a bar heater does. It moves heat from one place to another, using the same refrigeration process as your fridge. A reversing valve switches it between cooling, which moves heat out of the house, and heating, which brings heat in from the outside air.Moving heat takes far less electricity than making it. An electric heater turns one kilowatt of electricity into one kilowatt of heat. A heat pump air conditioner turns one kilowatt into about three kilowatts of heat. With solar, the panels supply the electricity and the heat pump makes each unit of it go about three times as far. There is more on the process in the Education Centre.

When to run it so the panels do the work

In summer, pre-cool the house in the afternoon. Turn the system on before the rooms get hot, while the sun is still on the panels. A system holding a set temperature uses less power than one working flat out to pull a hot house down, and it runs more efficiently while the outside air is cooler.In winter, run the heating in the middle of the day, when the panels are producing, and close the curtains at night to keep the warmth in.In hot weather, set the thermostat to 25 degrees or higher, and in cold weather to 18 to 20 degrees. The RET Good Energy Practice Guides put the cost of each degree beyond that at up to 10 per cent of the heating or cooling part of your bill.Close doors and vents to rooms you are not using, keep windows and doors shut while the system runs, and use the zones on a ducted system.

Lower emissions and less exposure to price rises

Solar power produces no emissions while it runs. Every hour of cooling or heating your panels cover is an hour you are not drawing from the grid, so the more of your air conditioning you run on daylight, the lower your household's emissions.The same shift protects your bills. Electricity prices in Australia have risen. Power from your own roof is not affected by the retail price, so a household that runs its air conditioning largely on solar has less of its comfort tied to what the grid charges. You still buy grid power at night and on overcast days.What matters is when you run the system and how efficient it is. On the Energy Rating Label, more stars means more efficient.

Government incentives may apply

Government schemes for rooftop solar and for efficient heating and cooling systems have existed at federal and state level, and they change. They are not listed here because they go out of date. Before you sign, check the current federal and NSW schemes yourself, and ask the dealer which apply to the system being quoted.An incentive lowers the purchase price, not the running cost, so it should not change the size or type of system you choose. A quote from an accredited member sets out the price and payment schedule in writing, so any rebate or discount should appear there, not as a verbal promise.

If the installation falls short

Adding solar does not change who is responsible for the installation. If a new domestic installation by an accredited member falls short of the ACDA Standards, the ACDA Guarantee applies. It is a written workmanship guarantee on new domestic installations by an accredited member, for contracts up to $25,000 including GST. ACDA engages an independent Chartered Engineer to investigate, report and advise, and arranges for defects to be corrected. It is not an equipment warranty, which stays with the manufacturer, and it is not a price guarantee. It sits alongside your rights under Australian Consumer Law.To raise a concern, complete the Dispute Resolution Form with your details, the member's details, what was installed and when, and what the problem is. Attach your quote, invoice and any photographs, and send it to the Dispute Resolution Committee at PO Box 253, Emu Plains NSW 2750, or [email protected]. Your solar system is a separate contract with its own installer, and a problem with the panels goes to them.

Before you sign

• The quote shows the calculated heating and cooling capacity, worked out by an approved method.
• You have checked the current federal and NSW schemes and asked which apply to the quoted system.
• Any rebate or discount is written into the price and payment schedule, not promised verbally.
• The system is reverse cycle, so winter daytime solar can run the heating too.
• You know how to set a timer or schedule so the system runs while the panels produce.

Every accredited member puts the calculated capacity your home needs in a written quote, so the system you run on solar is sized for the house. Check the business is a current member before you sign.