The “best” hot water system changes a lot depending on household size. Not because the technology is different, but because your hot water habits are different.
With two people, you can usually avoid overlap. With five people, overlap is hard to avoid, especially in the morning when showers, taps, and appliances can all run close together. That peak demand is what makes a system feel reliable or disappointing.
| Household | Best starting picks | Why they tend to work |
| 2 people | Continuous flow (16–20 L/min), or electric storage (125–160L), or gas storage (90–135L) | Lower peak demand, fewer simultaneous showers |
| 5 people | Continuous flow (26+ L/min), or storage (250–400L), or heat pump (300L+) | Higher peak demand, shower overlap is common |
If two showers can run at once in your home, size for that first. It’s the most common reason people “run out” even when the system looks big enough on paper.
2 people, continuous flow: Rheem 16L natural gas https://australianhotwater.com.au/product/rheem-16-litre-natural-metro-natural-gas-hot-water-system-price-installed-ed/
2 people, electric storage: Rheem 125L electric https://australianhotwater.com.au/product/rheem-125-litre-electric-hot-water-system-price-installed/
5 people, continuous flow: Rheem 26L natural gas https://australianhotwater.com.au/product/rheem-26-litre-natural-gas-hot-water-system-price-installed/
5 people, large storage: Dux 315L electric https://australianhotwater.com.au/product/dux-315-litre-electric-hot-water-system-price-installed/
5 people, heat pump: Sanden Eco Plus 315L https://australianhotwater.com.au/product/sanden-eco-plus-315-litre-heat-pump-price/
The one thing that decides the winner: shower overlap
| Question | If “No” | If “Yes” |
| Do you regularly run two showers at the same time? | You can often choose a smaller, simpler system | You need higher output (L/min) or a bigger tank buffer (or both) |
This is why a family of four in a one-bathroom unit can be fine with a smaller system, while a similar-size household in a two-bathroom home might struggle.
Instant/continuous flow options: https://australianhotwater.com.au/hot-water-systems/type/instant-hot-water/
Electric storage options: https://australianhotwater.com.au/hot-water-systems/type/electric-hot-water/
Peak demand made simple (how to estimate it)
| What might run at the same time | Typical flow rate |
| Standard shower | 8–12 L/min |
| High-flow / rainfall shower | 12–16 L/min |
| Kitchen tap | 6–8 L/min |
| Bathroom basin | 4–6 L/min |
How to use this: think about your busiest 60–90 minutes and add up what can run together. Two showers alone can push you into 20–30+ L/min territory, before taps are even counted. That’s why families often need either a high-capacity continuous flow unit or a larger storage system.
If your household is closer to “one shower at a time”: Rheem 16L continuous flow https://australianhotwater.com.au/product/rheem-16-litre-natural-metro-natural-gas-hot-water-system-price-installed-ed/
If your household is closer to “two showers at once”: Dux 26L continuous flow https://australianhotwater.com.au/product/dux-26-litre-natural-gas-hot-water-system-price-installed-installed/
System showdown table (what works best for 2 vs 5 people)
| System type | What it’s like at home | Best for 2 people | Best for 5 people | Most common mistake |
| Continuous flow | Hot water on demand (when sized right) | Great if you mostly run one shower at a time | Great if sized for overlap (often 26+ L/min) | Choosing a unit sized for one shower, then getting temp drops |
| Electric storage | A “tank” of hot water that refills over time | Simple and cost-effective when demand is low | Works if the tank is large enough for the morning rush | Installing a standard mid-size tank and expecting it to feel unlimited |
| Gas storage | Tank system with faster recovery than electric | Strong option where gas is available | Good when you want a buffer plus quicker bounce-back | Underestimating overlap (you can still drain a tank) |
| Heat pump | Efficient electric tank (steady recovery) | Great for lower running costs when sized properly | Great if you size up for peak periods | Undersizing because “it’s efficient” (efficiency isn’t peak output) |
Continuous flow (2 people example): https://australianhotwater.com.au/product/rheem-16-litre-natural-metro-natural-gas-hot-water-system-price-installed-ed/
Continuous flow (5 people example): https://australianhotwater.com.au/product/rheem-26-litre-natural-gas-hot-water-system-price-installed/
Electric storage (2 people example): https://australianhotwater.com.au/product/rheem-125-litre-electric-hot-water-system-price-installed/
Electric storage (5 people example): https://australianhotwater.com.au/product/dux-315-litre-electric-hot-water-system-price-installed/
Gas storage (family example): https://australianhotwater.com.au/product/rheem-170-litre-natural-gas-hot-water-system-price-installed/
Heat pump (2 people example): https://australianhotwater.com.au/product/sanden-eco-plus-250-litre-heat-pump-price/
Heat pump (5 people example): https://australianhotwater.com.au/product/sanden-eco-plus-315-litre-heat-pump-price/
Recommended sizing (simple starting points)
For 2 people
| Home setup | Continuous flow | Electric storage | Gas storage | Heat pump |
| 1 bathroom, minimal overlap | 16–20 L/min | 125–160L | 90–135L | 200–250L |
| 2 bathrooms, low overlap | 20–26 L/min (if needed) | 160–250L | 135–170L | 250–300L |
Continuous flow (16L): https://australianhotwater.com.au/product/rheem-16-litre-natural-metro-natural-gas-hot-water-system-price-installed-ed/
Electric (125L): https://australianhotwater.com.au/product/rheem-125-litre-electric-hot-water-system-price-installed/
Heat pump (250L): https://australianhotwater.com.au/product/sanden-eco-plus-250-litre-heat-pump-price/
For 5 people
| Home setup | Continuous flow | Electric storage | Gas storage | Heat pump |
| 2 bathrooms, overlap likely | 26+ L/min | 250–315L | 170–250L | 300L+ |
| 3 bathrooms, overlap common | 26+ L/min (may need planning or multiple units) | 315–400L | 250L+ | 300L+ (consider higher recovery/boost options) |
For a two-person household, the best hot water system is usually the one that’s sized sensibly and doesn’t make you pay for capacity you’ll rarely use. In most cases, that means a smaller continuous flow unit or a modest storage system that comfortably handles one shower at a time.
Continuous flow (26L): https://australianhotwater.com.au/product/rheem-26-litre-natural-gas-hot-water-system-price-installed/
Storage (250L electric): https://australianhotwater.com.au/product/rheem-250-litre-electric-hot-water-system-price-installed/
Storage (315L electric): https://australianhotwater.com.au/product/dux-315-litre-electric-hot-water-system-price-installed/
For a five-person household, “best” usually means planning for overlap. If multiple showers can run in the same window, you’ll get the most reliable results from a higher-capacity continuous flow system or a larger storage tank (including a correctly sized heat pump) that can handle the morning rush without temperature drops.If you want help choosing the right option for your home setup, you can compare system types here, or get in touch with us today to speak with an expert.