A solar hot water system is the original certificate product. It was creating STCs before rooftop PV took off, and in 2026 it still does. What has changed is the surrounding picture: heat pumps have taken most of the new-installation market, state programs have been reshaped around them and the federal count falls every year as the scheme runs down.
Our earlier guide to the solar hot water rebate explains the three layers and how to read a quote. This article is a national map for 2026: what applies everywhere, what depends on your state and how to compare a solar thermal quote with a heat pump quote on equal terms.
The federal layer applies everywhere
Registered solar water heaters earn STCs, whichever state you are in. The count is set by the model’s registered rating, your hot water climate zone and the deeming period, and the certificates are normally assigned to the installer, who shows the value as a discount. At the time of writing STCs have been roughly $38 to $40 each.
Take an illustrative system that registers 30 STCs for its zone and install year. At $38 to $40 that is $1,140 to $1,200. A heat pump registering 25 would be $950 to $1,000. The difference is small. What decides which is cheaper in practice is the gross price, the site and the running cost, not the certificate line. Remember these counts are illustrations. Use the register and your trader’s calculator for the real figure. See how many STCs a heat pump earns and heat pump STC calculator.
The deeming clock
For hot water the deeming runs to the end of the scheme in 2030, so each year the count for the same product falls. There is no mid-year step to worry about for hot water in the way there is for batteries, but the principle is the same: later installs earn fewer certificates. For a household deciding between buying this year and next, an illustrative 30-STC system might drop to a figure in the mid-20s, which at $39 is a loss of a couple of hundred dollars. Ask the installer to recompute for next year rather than guess.
State-by-state map
State programs change, so this table describes the mechanism and tells you where to look rather than quoting amounts.
| State or territory | What may sit on top of STCs | Where to check |
|---|---|---|
| Victoria | VEECs under Victorian Energy Upgrades; Solar Victoria rebate with a household income cap of $150,000 from 1 July 2026 | Essential Services Commission; Solar Victoria |
| NSW | ESCs under the Energy Savings Scheme; PRCs under the Peak Demand Reduction Scheme where an activity applies | IPART; NSW Government |
| South Australia | A state energy productivity scheme may support efficient hot water upgrades | SA energy department |
| ACT | An ACT energy efficiency scheme has supported hot water upgrades | ACT Government |
| Queensland, WA, Tasmania, NT | Federal STCs are the main layer; local or retailer offers may exist | State energy department pages |
Treat the lower rows as prompts to check rather than a promise. Victoria and NSW are covered in detail in our Victorian guide and our NSW guide.
Solar thermal versus heat pump on a rebate basis
A fair comparison puts both on net price and running cost.
| Question | Solar thermal | Heat pump |
|---|---|---|
| STC eligibility | Registered model, correct zone | Registered model, correct zone |
| Roof dependence | Needs good sun-facing space | None |
| Cold-climate performance | Needs boosting in poor sun | Works in most climates, check the model’s specification |
| State incentives | May qualify under state activities | Often the focus of state activities |
| Running cost | Low where sun is good, plus boosting | Low, using a share of the electricity of an element |
Where a state scheme targets heat pumps, the solar thermal option can miss a layer that the heat pump gets. Before deciding on technology, ask for both quotes with every incentive itemised.
Eligibility basics
For STCs a solar water heater needs the exact model on the CER register on the install date, correct classification as new, replacement or additional and a compliant installation by a licensed plumber with the right paperwork. See what makes a solar water heater eligible and which hot water systems are eligible for STCs.
From the desk: a quote that says “government rebate included” without a certificate count is unfinished. Ask for the STC count, the dollar value per certificate and the date it was calculated. Counts are easy to check and prices move, and an honest installer will show both.
For installers
Solar thermal volumes are lower than heat pump volumes, but the claim is the same: model, zone, installation type, photos, serials and a signed assignment form. Build one checklist for every hot water job and lodge complete claims. Our hot water STCs page shows how we settle them, and the pricing page lists the daily rate.
Choosing between solar thermal and a heat pump on a real roof
A solar water heater depends on a sunny, unshaded roof and a household with regular hot water use. A heat pump works where the roof cannot. If your roof faces south, is shaded by trees or is full of solar panels, solar thermal is a hard sell. If you already have a large PV system and a good export tariff, a heat pump that runs at midday can use your own power. If you have a family at home during the day and a suitable north-facing roof, solar thermal can be very efficient. The rebate is not the deciding factor, because the certificate line is similar. Ask each installer for the estimated annual running cost on your tariff, with the assumptions written down.
What to ask about the warranty
Both technologies are long-lived, and the warranty matters more than a few hundred dollars of rebate. Ask for the warranty on the tank, the collectors or compressor, and the labour, and ask who stands behind it if the installer stops trading. Our answer on what happens if an installer goes bust covers the certificate side of that risk. The rebate arrives as a discount on day one, and a warranty arrives as a promise for years, so it deserves equal attention.
What to do next
- Get two quotes, one solar thermal and one heat pump, with each incentive itemised.
- Check your state’s page for any program that sits on top of the STCs.
- Ask the installer to recompute the STC count for next year.
- Read the national pillar at /hot-water/ and the hot water resources.
For the wider hot water picture, see the hot water hub.