How rooftop solar makes electric floor heating close to free in Canberra

If you’ve got rooftop solar on your Canberra home, you’ve already paid for the energy that comes off the panels during the day. The trick is using it before the grid takes it back at the feed-in rate. Run your electric floor heating through the middle of the day and that’s exactly what happens. The heating runs for close to free.

We’ve been installing electric floor heating in Canberra since 1988. Over the past two or three years the question from new build clients and renovators has shifted from ducted gas or ducted reverse cycle to how do we use our solar to heat the house. Floor heating is the answer that keeps coming back, and the maths is simple enough to do on the back of an envelope.

Run the heating when the sun is shining

A 10kW solar system on a Canberra roof is generating well above what the average house uses through the middle of the day, even in winter. That extra generation goes back to the grid at a feed-in tariff of around 7 cents per kWh. You bought it for nothing and you’re selling it for almost nothing.

Run your floor heating between 10am and 3pm and the panels cover the draw. The system is heating your home on energy you’ve already paid for. Nothing leaves the meter going out.

The maths in plain numbers

Pick a typical Canberra family home with a 10kW solar system on the roof. When the floor heating is running it draws around 5kW. In the middle of a Canberra winter you’d run it about five hours a day, mostly through the middle of the day. Five hours at 5kW is 25 kWh of energy used per day.

Without solar, at the Evoenergy retail rate of 30 cents per kWh, that 25 kWh costs you $7.50 a day. Over a 30 day month that’s $225 a month just on heating. Across a four month Canberra winter from June through September you’d hand over about $900 to the grid.

With the 10kW solar setup, schedule the heating to come on between 10am and 3pm. The panels are covering the 5kW draw. The grid sees almost nothing.

The kWh you’d have exported back for 7 cents is now used in your floor where it’s worth 30 cents. Every solar kWh into the heating saves you 23 cents.

In practice a Canberra family heating their home on solar pays $30 to $80 a month for heating across the winter months, instead of $225 without panels. Over a winter that’s a saving in the order of $600 to $800 compared to a no-solar build, and several times that compared to ducted gas.

The same maths works whether you have undertile heating on a renovation or in-slab heating on a new build. As long as the heating is running during the solar window, you’re using daytime energy at the grid rate of 30 cents instead of selling it for 7.

Two paths depending on the build

If you’re renovating and the floor is already in, you’re looking at undertile heating. We use our DM20 cable in self-leveller or screed, going on top of the existing floor under tile, timber or polished concrete. DM20 is the most-specified renovator and builder product we sell. It’s quick to install, heats up fast, and gives you the same solar-offset benefit once it’s running.

If you’re pouring a new slab, you’re looking at in-slab heating. We use VCD35 cable on the upper rebar mesh at 200mm centres before the pour. You get the solar offset plus extra thermal storage, which means heat stays in the house for hours after the system has turned off.

Either way you get the same outcome. Heating that costs close to nothing through the day. Comfort that lasts through the evening. No moving parts. No gas bill.

What’s driving the shift in the ACT

A few things have landed at once.

The gas phase-out. Since late 2023 new developments in the ACT have not been connected to mains gas. If you’re building in Whitlam, Molonglo Valley, Throsby, Taylor or anywhere else in the newer estates, gas isn’t on the table. Electric is the only sensible option, and once you’re electric, floor heating on solar makes sense for the running cost reasons above.

Solar uptake is high and rising. The ACT has one of the highest per-capita rates of rooftop solar in the country. Most new builds put 6.6kW or 10kW on the roof as a matter of course. A lot of established homes have done the same in the past five years. That generation has to be used somewhere, and using it in your floor beats exporting it for almost nothing.

Grid prices are climbing. Evoenergy lifted its regulated retail rates again in July 2025 and the trajectory is up not down. Anything that lets you shift consumption off the grid and onto your own panels has gone from a nice-to-have to a real number on the monthly bill.

The architects have noticed. We work with a lot of Canberra builders and designers who specify floor heating as standard on new builds with solar, rather than as an upgrade. The combination is part of how new homes hit the seven-star NatHERS rating without overbuilding the envelope.

What to do next

If you’re building or renovating in Canberra and you’ve got solar on the roof or in the design, get a quote off us before the floors go in. We’re at 23 Winchcombe Court Mitchell, open weekdays, and we’ll turn around a takeoff and quote in two business days.

Send us the plans, tell us the rooms you want heated, and tell us what’s on the roof. We’ll do the rest.