Running Reverse-Cycle Air Conditioning on Solar and a Battery in the Northern Rivers: Load Sizing, Ducted vs Split, Pre-Cooling and a Calculator

Checked and updated by our licensed electricians: October 2026

Air conditioning is the biggest load most Northern Rivers homes have, the one that sets the size of the solar and the battery, and the one that runs mostly after the sun has gone. This guide, written by local electricians who size systems around it every week, explains how much power reverse-cycle units really draw (and how to read it off the energy label), the difference ducted and split systems make, how to pre-cool a house on your own solar so the battery coasts through the evening, how we size solar and a battery around air conditioning, what happens in winter and in a blackout, and what we do and do not do. We do not sell air conditioners and we name no brands; we make the roof and the battery carry whatever you choose. The calculator at the top turns your unit, hours and habits into kWh a day and what that asks of solar and a battery. No dollar figures: the kWh and your tariff give them.

On this page: The calculator: what your air conditioning asks of solar and a battery · How much power air conditioning really uses · Reading the energy label · Ducted vs split systems in a solar home · Daytime: pre-cooling on solar · Evening and night: the battery · Sizing solar and a battery around air conditioning · Heating in winter, and the shoulder months · Air conditioning in a blackout · What we do, and the referral · Questions we get asked

Air conditioning on solar and a battery: calculator

Six taps: your unit (or plan), the season, hours a day, when it runs, your solar and whether you have a battery. The result shows on screen straight away with the daytime and evening split; sending it to your phone is optional.

How much power air conditioning really uses

The number on the box, 2.5 kW or 7 kW or 14 kW, is cooling capacity, not electricity. Modern inverter reverse-cycle units move three to five units of heat for each unit of electricity, so the electrical draw (the rated power input on the label) is roughly a quarter to a third of the capacity. Typical figures:

Two things matter more than the table. First, inverter units run near their rated input while they pull a hot room down and then throttle back to a fraction of it, so the average over an hour is well below the label; the 60 per cent we use is a working figure for a house that is already cool. Second, the set point rules everything: a unit holding 26 degrees on a 32 degree day works a fraction as hard as one holding 20. The label’s own annual kWh figure (next section) is the honest planning number.

Reading the energy label

Every air conditioner sold in Australia is tested to the Australian standard and registered at energyrating.gov.au, and carries the Zoned Energy Rating Label. It shows a seasonal star rating and an estimated annual energy use in kWh for heating and for cooling in three climate zones (hot, average, cold); the Northern Rivers reads the hot zone. The label also gives cooling capacity at 35 degrees and heating capacity at 7 and 2 degrees, and the spec sheet gives the rated power input for each. For solar and battery design, the rated input (kW) tells you what the unit asks of the inverter at once, and the annual kWh for the hot zone tells you what it asks of the roof over a year. The official advice we agree with: the most important thing is the right size for the space; an oversized unit cycles and wastes power, an undersized one runs flat out all evening.

Ducted vs split systems in a solar home

Splits cool the room you are in. Each draws 0.7 to 2.4 kW, you can run the living room on the panels in the afternoon and one bedroom on the battery at night, and a single-phase solar and battery system carries them without thought. They are the solar-friendly choice.

Ducted cools the whole house from one unit of 10 to 18 kW capacity drawing 3 to 5.5 kW whenever it runs. It gives even comfort and a tidy ceiling, and it costs more electricity than people expect, because it is cooling rooms nobody is in. Zoning (dampers that shut off bedrooms by day and living areas by night) halves that; so does a 26 degree set point. On the electrical side, ducted plus an EV charger plus a large battery is the combination that pushes a home to three-phase power, and it is the load that most often trips a single-phase battery system in a blackout when the oven is on too. If you are choosing now, size the ducted unit to the zones you will actually run, not the whole floor plan.

For a new home the choice belongs on the plans with the switchboard and the phase: see our BASIX, solar and battery guide for a new build and single phase vs three phase for solar and batteries.

Daytime: pre-cooling on solar

The best air conditioning strategy in a solar home costs nothing: use the house as the battery. From about 1 or 2pm on a hot day, when the panels are near their peak and the rooms are not yet hot, close the house up, set the unit to 24 to 26 degrees and let it run on the roof’s output. By the time the sun drops the walls, the slab and the furniture are cool and the unit either idles or goes off, with ceiling fans moving the air. Households that do this report a comfortable house into the late evening with the battery barely touched. It works in proportion to the building: insulation, shading on the western glass and ceiling fans make it work; an uninsulated room with afternoon sun on the windows gives the cool back in an hour. A Sigenergy or GoodWe system can switch a circuit on when the panels are exporting, which is a neat way to start the pre-cool automatically.

Evening and night: the battery

Whatever is left after pre-cooling is the battery’s job. A single split averaging about 0.6 kW through an eight-hour night is about 5 kWh, which a 16 kWh GoodWe or 18 kWh Sigenergy carries along with the rest of the house. Two or three splits is 10 to 14 kWh; ducted for the whole house on a hot night is 20 to 30 kWh, which is a large battery or a shorter run and is exactly why pre-cooling matters. Two rules for the design: the battery’s kWh is sized to the evening air conditioning plus the normal evening load (8 to 12 kWh for most homes), and the inverter’s kW is checked against the unit’s rated input plus the kettle and the oven; a single-phase home battery system supplies about 5 to 10 kW at once.

Sizing background: what size battery do I need? and the Northern Rivers home battery buyer’s guide.

Sizing solar and a battery around air conditioning

1. Split the air conditioning into day and evening kWh from the unit’s rated input, your hours and when you run it (the calculator does this).
2. Solar carries the daytime share plus the house. Each kW of panels makes about 3.8 kWh on an average day here, two thirds of it between 10am and 4pm, and more on the clear summer days when the air conditioning runs; a medium split barely registers, ducted wants a 10 kW or larger system.
3. The battery carries the evening share plus the normal evening load, in GoodWe 8 kWh or Sigenergy 9 kWh modules, with the inverter’s kW checked against the unit’s rated input.
4. Check winter. The same unit heats in July on about 30 per cent less solar; a roof that fills the battery in June with the heating running is the real test.
5. Design the habits in: pre-cool from early afternoon, 24 to 26 degrees, zoning, fans, shading. They are worth a battery module.

Put your own numbers in with the solar and battery price calculator and how big a solar system do I need?.

Heating in winter, and the shoulder months

Reverse-cycle is also the efficient way to heat a Northern Rivers home for the few cold weeks: the same three to five units of heat per unit of electricity, no flue, nothing in the room. The pattern flips: heating runs in the early morning and the evening, exactly when the solar is weakest and the battery is doing the most, so the winter test is whether the roof refills the battery by mid-afternoon on a short June day with the heating on. In the long shoulder months the unit runs little, and a solar home exports most of its output; that is when a battery’s job is the evening lights and cooking rather than the weather.

Air conditioning in a blackout

A home battery system set up for whole-home backup runs the air conditioning in an outage, with two limits. Energy: a 16 to 27 kWh battery running one split (about 0.6 kW average) plus the fridge, lights and a pump lasts most of a night and resets on the next sunny day; ducted for the whole house drains it in a few hours. Power: a single-phase system supplies about 5 to 10 kW at once, so run one unit at a time and not with the oven. A three-phase ducted unit is a special case: the most common battery backup systems cannot run a three-phase motor load at all, so in an outage it stays off unless the backup is designed for it from the start. In the heatwave-then-storm pattern we get, the sensible plan is a cool house before the storm and one bedroom unit after it.

Work it out for your own appliances with the blackout battery runtime calculator, and compare the options in generator or home battery for Northern Rivers blackouts.

What we do, and the referral

Sun Connect Solar is a solar, battery and EV charger electrical contractor. We design the solar and the battery to carry your air conditioning, run the dedicated circuits, set the battery schedule and the export-triggered pre-cool, and advise on single or three phase. We do not sell or install air conditioners and we recommend no brand; the energy label and a good air conditioning installer do that. If you tick the box in the calculator, we pass your details to a local air conditioning installer we work with so they can quote the unit, and we may receive a referral fee for the introduction, which does not change the price you pay. If you do not tick it, your details stay with us and we only send you the result and this guide.

Questions we get asked

Can solar panels run my air conditioner?

Yes, during the day. A medium split system (3.5 to 5 kW of cooling) draws about 1 to 1.2 kW at full tilt and well under that once the room is at temperature, so a 6.6 kW solar system making 3 to 4 kW at midday carries it with room for the house. A ducted system for a whole home draws 3 to 5 kW when working hard, which is most of what a 6.6 kW system makes and comfortable for a 10 to 13 kW system. The catch is timing: most air conditioning runs in the evening, after the panels have stopped, which is where a battery (or pre-cooling the house from mid-afternoon) comes in.

How much power does a reverse-cycle air conditioner use?

Read the rated power input on the unit’s label or spec sheet, not the cooling capacity. Modern inverter units deliver three to five units of cooling or heating per unit of electricity, so a 2.5 kW unit draws about 0.7 kW, a 3.5 to 5 kW unit about 1 to 1.4 kW, a 7 kW unit about 2 kW, and ducted systems about 3 kW (10 kW) to 5 kW (16 kW or more) at full output. Once the room is at the set temperature an inverter unit throttles back and the average draw over an hour is around 60 per cent of that. The Zoned Energy Rating Label gives an estimated annual kWh for your climate zone; the Northern Rivers sits in the hot zone.

Will a home battery run the air conditioning at night?

A single split, yes, all night. Work it out from the rated input: a 1 kW unit averaging about 0.6 kW while holding temperature uses about 5 kWh over an eight-hour night, so a 16 kWh GoodWe or 18 kWh Sigenergy battery runs it and the rest of the house comfortably. Ducted for a whole house on a hot night is 20 to 30 kWh, which is a large battery or a shorter run, which is why we pre-cool on solar and let the thermal mass carry the evening. A single-phase battery system supplies about 5 to 10 kW at once, so a big ducted unit starting with the oven on can trip it; in a blackout run the air conditioning on its own.

What is pre-cooling and does it work?

Running the air conditioning from early or mid-afternoon on your own solar so the house, its walls, slab and furniture are cool by the time the sun drops, then letting the unit idle or switching it off for the evening. Households that do it report the house staying comfortable well into the night with the battery barely touched. It works best in a well-insulated, shaded home with ceiling fans to move the cool air; a tin shed with no insulation gives it back in an hour. Set the thermostat to 24 to 26 degrees rather than 20 and the unit runs at a fraction of its input.

Ducted or split systems for a solar home?

Splits are the solar-friendly choice: you cool the room you are in, each unit draws 0.7 to 2 kW, and you can run the living room from the panels in the afternoon and one bedroom from the battery at night. Ducted gives whole-house comfort and a tidier look but draws 3 to 5 kW whenever it runs, so it needs a bigger solar system, a bigger battery, zoning so you are not cooling empty rooms, and often three-phase power when it shares the house with an EV charger and a large battery. Either way the energy label’s rated input and annual kWh tell you what you are buying.

Does air conditioning change the size of solar system I need?

It is usually the single biggest variable. A medium split used five hours a day adds roughly 3 to 4 kWh a day, mostly in the evening; a ducted system used eight hours on hot days adds 15 to 25 kWh a day on those days. We size the solar for the daytime share plus the house, and the battery for the evening share plus the normal evening load, then check that the roof can fill the battery in winter when the air conditioning is heating instead. The calculator on this page gives the first numbers; a site visit and your bills give the real ones.

Does Sun Connect Solar install air conditioners?

No. We are solar, battery and EV charger electricians; we design the solar and battery to carry your air conditioning, run the dedicated circuits, set up the timers and the battery schedule, and advise on single or three phase. We do not sell or install air conditioners and we name no brands. If you tick the box in the calculator we pass your details to a local air conditioning installer we work with so they can quote the unit, and we may receive a referral fee for the introduction, which does not change your price; if you do not tick it, your details stay with us.

How does a battery cope with a heatwave?

A heatwave is the one time the evening load is biggest and the day’s solar is also biggest, so a well-sized system handles it: pre-cool hard from 1 or 2pm on the panels, run the battery through the evening on the rooms you are using, and let the unit idle overnight at 26 degrees. The storm that often follows is a different problem: see our blackout battery runtime calculator for what the battery runs when the grid is out, and remember that in an outage the air conditioning runs one unit at a time.

Sources

SolarQuotes: “Air conditioning: how to choose the right system in Australia”, “Evaporative cooling vs reverse cycle air conditioning” (reverse cycle is the better choice with solar, better again with a battery; pre-conditioning on a timer), “The air con efficiency rating you should really care about”, “Air conditioners will heat your home cheaper than gas” and “Do you really need a 3-phase battery to back up your 3-phase home?” (common backup systems cannot run a three-phase load); Australian Government energyrating.gov.au: Zoned Energy Rating Label guidance for air conditioners (zones, annual kWh, capacity at 35, 7 and 2 degrees, AS/NZS 3823.2 testing); EcoGeneration, “The aircon-solar mismatch” (how inverter units behave electrically); CHOICE air conditioner running-cost method and tests; Renew magazine pre-cooling case studies; Victorian Government home heating and cooling buyer’s guide; makers’ published rated power inputs for typical split and ducted capacities; our own blackout and battery sizing calculators for the household figures. Full list in our research note. Checked October 2026.

More from Sun Connect Solar

• All our free solar and battery calculators
• How long would a battery run my house in a blackout?
• What size battery do I need?
• Running your pool on solar
• How big a solar system do I need?
• BASIX, solar and batteries for a new build
• Northern Rivers home battery buyer’s guide
• Home battery installation in the Northern Rivers