Gas Hot Water System Cost: Storage vs Continuous Flow
What a gas hot water system costs installed, storage versus continuous flow, and the gas fitting, flue and compliance extras that change a quote.
A gas storage hot water system typically costs $2,100 installed, and a continuous flow unit $2,250, both including GST. Across all system types, a typical replacement runs $1,650 – $2,750, so the gas options sit within that spread. The gap between two gas quotes usually comes from the extras, not the unit.
Storage vs continuous flow: installed prices
| Material | Typical | Usual range | Lifespan |
|---|---|---|---|
| Electric storage (250-315 L) | $1,600 | $1,250 – $2,100 | 8-12 years |
| Gas storage (135-170 L) | $2,100 | $1,650 – $2,750 | 8-12 years |
| Continuous flow gas (20-26 L/min) | $2,250 | $1,750 – $2,950 | 12-20 years |
Our figures assume a straight swap, with the old unit removed and the new one connected. They include the unit, labour, fittings and GST. We build them from labour hours multiplied by local rates, plus materials, then check the result against market prices and real quotes.
Which one suits your household
Gas storage (135–170 L) keeps a tank of heated water ready. It is simple, familiar and often the easiest like-for-like swap. The trade-off is standing heat loss, because the tank keeps reheating whether you use the water or not. A household with a few showers back to back can also run the tank out.
Continuous flow (20–26 L/min) heats water only when a tap opens. There is no tank to run out, so it suits large households and long showers. It also takes up less room, usually on an outside wall. The unit price often differs from storage, but a tighter fit with your existing pipework can change the total. Check the flow rating against how many outlets you run at once.
A simple rule of thumb:
- Choose storage if you want a like-for-like swap in the same spot and a modest household.
- Choose continuous flow if you want endless hot water, or you are short on space.
- If neither suits, compare electric storage in the table above. It avoids the gas work, though running costs differ.
The extras that turn up on gas quotes
The unit price is rarely the whole story. Ask your installer whether each of these is included or itemised:
- Gas fitting. A new gas line, a longer run, or a larger-bore pipe to feed a continuous flow unit can add to the bill. Gas work must be done by a licensed tradesperson.
- Flue. A continuous flow unit mounted in a new spot may need a different flue route or terminal clearances. A like-for-like swap in the same spot is usually cheapest.
- Relocation. Moving the unit from where the old one sat means new pipework for gas, hot and cold water.
- Compliance. Plumbing and gas work needs licensed trades under state licensing. Ask for the licence details and whatever compliance paperwork applies in your state.
- Valves and fittings. Tempering valves, pressure-limiting valves and isolation valves are sometimes extra lines on a quote.
- Old unit disposal. Usually included, but confirm.
- Electrical. Many gas units still need a power point nearby for the ignition and controls. If one is not there, a licensed electrician has to add it.
A quote that looks cheap often leaves several of these out. A fixed price covering all of them is easier to compare.
When the swap is not like-for-like
Our changeover option shows how much a switch can move the price. Moving from gas to a system that needs a dedicated electrical circuit adds electrical work, and the electric storage figure with a new circuit is $2,400. Compare that with the same-spot figure of $2,100. If your quote is far above the typical range for your system, ask which of the extras above explains it.
Is it worth looking beyond gas?
It is worth pricing alternatives before you commit. A heat pump hot water system costs more upfront, with a typical installed price of $4,500. Heat pump hot water prices are usually quoted after STCs (small-scale technology certificates), a federal discount that steps down each year until the scheme ends in 2030. Check that any heat pump quote you receive shows the discount, so you compare like with like. See our guide: Heat pump hot water.
If you have or are considering rooftop panels, our solar guide shows how that fits with electric hot water: Solar panels.
For the full picture on swapping any system, including electric storage, see Hot water system replacement.
How to get a fair quote
- Get at least three quotes for the same system type and size.
- Ask each installer to list gas fitting, flue, valves, disposal and compliance work separately.
- Confirm that quotes include 10% GST, as ours do.
- Check the installer's licence for plumbing and gas fitting.
- Run the quotes through our quote checker ("is my quote fair" tool) to see how each sits against the typical range.
Treat the quote checker as a guide, not a verdict. Site conditions such as access, a long gas run or a tricky flue can justify a higher price, as long as your installer can explain why.
The bottom line
For a like-for-like swap in the same spot, expect installed prices near the typical figures above. Costs rise when the unit moves, the flue changes or new gas or electrical work is needed. Decide on the system type first, then compare itemised quotes.