Choosing the right size hot water system for your Joondanna home stops cold showers during busy times & avoids paying for capacity you don’t use. Focus on people, bathrooms, what runs at the same time, & how quickly the system recovers.
What “right size” means
A system is right when it:
- Keeps showers hot in the busiest hour (often mornings).
- Handles two things at once (e.g., two showers, or a shower & kitchen tap).
- Recovers fast enough for the next person.
- Doesn’t waste money on oversize equipment.
Step-by-step sizing
- Count people & bathrooms
More people & bathrooms usually mean more overlap. Teenagers & guests increase demand. - Map the busiest hour
List what actually runs together: showers, bath fills, kitchen tap, basin, dishwasher, washing machine. If two showers often overlap, size for that as a minimum. - Pick a system type to match your pattern
- Instantaneous (continuous-flow): heats water as you use it. Good when space is tight & showers overlap.
- Storage (electric, gas, heat pump): keeps hot water in a tank. Good for back-to-back use.
- Solar + booster: lowers bills but still needs the right tank for mornings & winter.
- Instantaneous (continuous-flow): heats water as you use it. Good when space is tight & showers overlap.
- Allow for winter
Mains water is colder in winter, so systems work harder. Add a small buffer so performance stays steady on chilly mornings. - Use simple upgrades
Water-saving shower heads reduce peak demand while keeping comfort high, which can let you choose a smaller, cheaper system.
Quick size guide (rules of thumb)
- 1–2 people, 1 bathroom, one shower at a time
Instantaneous: small unit
Storage: 125–160 L - 3–4 people, 1–2 bathrooms, two showers may overlap
Instantaneous: mid-size unit
Storage: ~250 L - 4–6 people, 2+ bathrooms, frequent overlaps or bath use
Instantaneous: large unit (or two smaller in parallel)
Storage: 315–400 L - Studio/granny flat, 1 person
Instantaneous: compact unit
Storage: 80–125 L
(If two showers plus a kitchen tap often run together, move up one size.)
Instantaneous vs storage: which suits you?
- Instantaneous (continuous-flow):
Pros: effectively endless hot water within unit capacity, small footprint.
Check: choose a unit that covers your busiest overlap (e.g., two showers). - Storage (electric, gas, heat pump):
Pros: strong for back-to-back use; simple to understand.
Check: pick a tank that covers your first busy hour, & confirm the heater recovers fast enough for the next round. - Heat pump (storage type):
Pros: lower running costs than standard electric.
Check: outdoor space & noise placement on smaller blocks. - Solar + booster:
Pros: lower bills across the year.
Check: roof space, shade, & a tank size that fits the morning routine.
Common mistakes
- Buying by bedroom count instead of real overlap.
- Choosing an instantaneous unit that’s too small for two showers at once.
- Picking a storage tank that can’t handle three back-to-back showers.
- Ignoring likely changes (teens, an added ensuite, or short-stay guests).
- Poor siting (venting, clearances, or noise) that limits performance.
Simple scenarios
- Two-person villa, one bathroom: one shower at a time → small instantaneous or 125–160 L storage.
- Family of four, two bathrooms: two showers often overlap → mid-size instantaneous or ~250 L storage.
- Five or six people, 2.5–3 bathrooms, bath on weekends: frequent overlaps → large instantaneous (or two smaller) or 315–400 L storage.
- Single-occupant studio: compact instantaneous or 80–125 L storage.
Cost-smart tips
- Fit water-saving shower heads to lower peak demand & system size.
- If space limits tank size, choose faster-recovery models instead of a bigger tank.
- Insulate long hot-water runs to cut heat loss.
- Compare life-cycle cost (purchase + running), not just the ticket price.
Conclusion
Size to the real peak, not guesswork. Count people, map overlaps, choose a system that meets the busiest hour, allow a winter buffer, & check recovery. For selection, installation & compliance in the area, a licensed Plumber Joondanna can confirm the right size for your layout, bathrooms & busy hours. For repairs, upgrades or urgent issues, a Hot water Plumber Joondanna can match real-world use to the correct capacity so you avoid cold showers & overspend.