Last reviewed: July 2026 · How we research these costs · Energy guidance: EECA — Energy Efficiency
Our old copper cylinder in Botany died on a July morning, mid-shower, and chasing down a replacement that same week taught me more about hot water than I expected to learn twice in one career. I’m Steve Mackay, a registered plumber who’s spent 19 years working across East Auckland — Botany, Flat Bush, Howick, Pakuranga — on everything from gasfitting to full cylinder swaps. If yours hasn’t died yet, you’ve got something I didn’t have that morning: time to pick a system on merit instead of panic. Here are the real numbers for the four systems Auckland homeowners actually choose between, and the trade-offs nobody mentions until the invoice turns up.
Key takeaways
- Four systems cover nearly every Auckland replacement: mains-pressure electric, gas continuous flow, hot water heat pump and solar.
- The cheapest system to buy is rarely the cheapest to run — a family of four can spend $250–$450 a year on a heat pump against $800–$1,300 for a standard electric cylinder.
- A heat pump suits Auckland’s mild climate and usually pays back its higher price in five to seven years for a busy household.
- Gas continuous flow only stacks up if you’ve already got reticulated gas at the boundary or room for LPG bottles.
- A like-for-like swap usually needs no building consent, but must be done by a licensed plumber, and any gas work by a certifying gasfitter.
- On mains-pressure cylinders a working tempering valve delivering water at 55°C is a safety essential, not an optional extra.
In this guide
- The four systems I get asked to quote
- What it actually costs installed
- How the four systems stack up side by side
- Which system actually suits your household
- Consent, gasfitting and the safety bits that matter
- Getting the most life out of whichever you choose
- The small print installers don’t always volunteer
- Questions I get asked before someone signs off
The four systems I get asked to quote
Nearly every job comes down to one of these four, and each one fits a different household and section.
- Mains-pressure electric cylinder: the default like-for-like replacement. Simple, reliable, and cheap to install if a cylinder’s already there. The running cost is where it bites.
- Gas continuous flow (instant): no cylinder taking up cupboard space and endless hot water. Needs reticulated gas or LPG bottles, which is common enough in newer Botany and Flat Bush builds.
- Hot water heat pump: pulls a fraction of the power a resistive element does. Costs more up front, pays off fastest for a household that runs a lot of hot water.
- Solar hot water: roof panels plus a cylinder. Biggest spend, slowest payback, and Auckland’s grey winters mean you’re still running an electric or gas booster regardless.
Which of the four is right for you is less about which is “best” in the abstract and more about two things: what fuel you’ve already got at the boundary, and how much hot water your household actually gets through in a day. Get those two straight in your head before you ring anyone for a quote and the shortlist usually narrows itself to one or two before a plumber has even walked up your drive.
What it actually costs installed
These are standard-swap prices from a registered plumber or gasfitter, GST included. Awkward access, relocating the unit, or bringing old wiring up to scratch will push any of them higher.
| System | Typical installed cost (incl. GST) | Typical annual running cost* |
|---|---|---|
| Mains-pressure electric cylinder (180–300L) | $2,200 – $4,500 | $800 – $1,300 |
| Gas continuous flow (instant) | $2,500 – $4,800, more if gas lines need running | varies with usage |
| Hot water heat pump | $4,500 – $8,000 | $250 – $450 |
| Solar hot water (with booster and cylinder) | $6,500 – $12,000 | varies with boost settings |
*figures are for a family of four. I’ve left gas and solar out of the direct comparison because their running cost swings too much with usage and booster settings to give one honest range — but electric versus heat pump is a fair fight, and it’s not close. The cheap option to buy is rarely the cheap option to run: a standard electric cylinder for a family of four can chew through $800 to $1,300 a year in power, against $250 to $450 a year for a heat pump doing the same job. Over a ten-year life, that gap covers the higher purchase price on its own.
How the four systems stack up side by side
Once you line them up next to each other, the choice usually sorts itself out. Here’s the same four systems laid out the way I’d sketch them on the back of a quote — what each one suits, the shape of the cost, and the one thing about each that tends to catch people out after they’ve signed.
| System | Best suited to | Cost picture | The catch |
|---|---|---|---|
| Mains-pressure electric cylinder | Light-to-moderate users and straight like-for-like swaps | Cheapest to install, dearest to run | The power bill climbs with every shower |
| Gas continuous flow (instant) | Bigger households with gas already at the boundary | Mid-range to install, running cost tracks usage | Needs reticulated gas or LPG; no stored tank to fall back on |
| Hot water heat pump | All-electric homes chasing the lowest running cost | Higher to install, cheapest to run | Outdoor unit hums and may need its own circuit |
| Solar hot water | Owners staying put long-term who want the lowest energy draw | Highest to install, boost cost varies | Still needs an electric or gas booster through grey winters |
The pattern I point out to nearly everyone is the top-to-bottom trade running through that table: the cheaper a system is to install, the more it tends to cost you every year it runs, and the reverse holds too. Electric is quick and cheap to drop in but the dearest to feed; a heat pump stings on the day but claws it back month after month. Which end of that trade suits you comes down to how long you plan to stay in the house and how much hot water actually goes through it — not to which unit looks smartest in the brochure.
Which system actually suits your household
A retired couple in a two-bedroom Botany townhouse with light hot water use won’t get their money back on a heat pump before it’s worn out, so a straight mains-pressure cylinder swap is the sensible call. A family of five running back-to-back showers is exactly who a continuous-flow gas unit or a heat pump is built for. Already got reticulated gas at the boundary? Continuous flow is hard to beat for convenience. All-electric and chasing the lowest running cost? The heat pump wins on the numbers even though it costs more today.
One thing worth flagging on tighter Botany and Flat Bush sections: a heat pump has an outdoor unit that hums. Check where it’ll sit against your neighbour’s bedroom wall and your boundary line before you sign anything — on an infill site it matters more than most people expect.
Consent, gasfitting and the safety bits that matter
A like-for-like hot water replacement usually doesn’t need building consent, but it has to be done by a licensed plumber, and any gas work by a certifying gasfitter. New or relocated gas appliances carry their own compliance requirements — worth confirming what applies through Building Performance before work starts. Mains-pressure cylinders also need a working tempering valve to keep water delivered to the tap at a safe 55°C, which guards against both scalding and Legionella building up in the cylinder. If you’re in an older home, my rundown of common plumbing problems in older Auckland homes covers the pipework issues that tend to surface once you start pulling a cylinder out.
Getting the most life out of whichever you choose
Whichever system goes in, a bit of upkeep is the difference between reaching the far end of its life and replacing it early. On a mains-pressure cylinder the sacrificial anode is the part quietly doing the work — it corrodes so the steel tank doesn’t, and once it’s spent the cylinder starts eating itself from the inside. Having it checked partway through the cylinder’s life is cheap insurance against exactly the kind of early failure that caught me out that July morning.
The tempering valve is the other component worth keeping honest. It’s what holds the water reaching your taps at that safe 55°C, and it does wear over time — if your hot water suddenly runs hotter or cooler than it used to, that valve is usually the culprit and it’s a quick swap for a plumber. Heat pumps and continuous-flow gas units earn from an occasional service too: clearing leaves and debris off a heat pump’s outdoor unit keeps it pulling heat efficiently, and a gas unit’s burner and filters are worth a periodic look. None of it is dramatic, but it’s the quiet maintenance that decides whether you get ten years or fifteen out of the spend.
The small print installers don’t always volunteer
Ask any installer three things before you book them in: what warranty covers the unit and the workmanship separately, whether the quoted price includes removing and disposing of the old cylinder, and whether your switchboard or gas supply needs upgrading. Older Botany homes still on original wiring sometimes need a dedicated circuit run for a heat pump, and that electrical work is a separate cost that some quotes quietly leave out until the day of install.
Questions I get asked before someone signs off
Is a hot water heat pump worth it in Auckland’s climate? For a household using a decent amount of hot water, yes. Auckland’s mild temperatures suit heat pumps well — they only work harder and less efficiently in genuine cold, which we rarely get. The running-cost saving over a standard cylinder usually pays back the higher purchase price within five to seven years.
How long does a hot water cylinder last? A good mains-pressure cylinder lasts around 10 to 15 years in Auckland, sometimes longer. Our water isn’t especially hard, so it’s the anode wearing out that usually ends a cylinder’s life, not scale. If yours is past the decade mark and starting to leak or run rusty, get the replacement planned before it fails on you mid-shower like mine did.
Can I switch from electric to gas hot water easily? Only if you’ve got reticulated gas at the boundary or room for LPG bottles. Running a brand-new gas connection can cost more than the unit itself, so get that priced first. If gas isn’t already on site, a hot water heat pump is usually the smarter way to cut running costs without adding new infrastructure.
Do I need building consent to replace a hot water cylinder? A straight like-for-like swap usually doesn’t need building consent, but it still has to be done by a licensed plumber, and any gas work by a certifying gasfitter. New or relocated gas appliances carry their own compliance requirements, so it’s worth confirming what applies before the work starts.
What size hot water cylinder does an Auckland household need? It comes down to how many people draw hot water at once. A couple or small household is usually fine at the lower end of the 180 to 300 litre range, while a busy family of four or five wants the larger end — or a continuous-flow unit that never empties. Undersize it and you’ll run cold mid-shower; oversize an electric cylinder and you’re paying to keep water hot you never use. Sizing and placement get decided together, which is why a West Auckland plumber will ask about the run to the furthest tap before recommending a cylinder.