Commercial Water Boiler Buying Guide: Autofill Sizes & Output Explained
Quick answerA small café serving 30–60 hot drinks a day is well covered by a 30L/hr wall-mounted autofill boiler. Once you're regularly queuing for the urn — church halls, staff canteens, bubble tea and coffee shops at peak service — step up to 50–70L/hr. If you don't have a spare wall or plumbing run for a wall-mounted unit, a freestanding countertop boiler gives you the same output without the install.
Run out of hot water at 8:45am on a Saturday and every order behind it stalls — the till queue backs up, the coffee machine waits on you instead of the other way round, and regulars notice. A commercial water boiler is one of the cheapest pieces of equipment in a café, yet it's the one most likely to quietly become the bottleneck if it's undersized for the till speed you actually run. This guide walks through how output and tank size are measured, how to size a boiler against your real order volume, and compares Keloo's autofill range so you can pick the right one first time.
Autofill vs manual fill — what the numbers mean
Every commercial boiler is described by two figures, and mixing them up is the single most common buying mistake:
- Output (L/hr) — how much boiling water the element can reheat and deliver per hour once it's up to temperature. This is the number that matters for a busy service, because it tells you how fast the tank recovers between draws.
- Tank capacity (L) — how much water is sitting ready to pour right now. A bigger tank buys you a deeper buffer during a sudden rush, but it's the output figure that decides whether you can keep up all morning.
All of Keloo's boilers are autofill — plumbed to a mains water line, they top themselves up automatically so you never lift a kettle or top up a manual reservoir mid-service. A manual-fill boiler is cheaper up front and doesn't need a plumbed connection, but every refill is a hands-off-the-till moment; for anything busier than a very low-volume kiosk, autofill pays for itself in the first few weeks.
How to size a boiler to your order volume
Work from cups per hour, not cups per day — a boiler only has to keep up with your peak hour, not your daily average. As a rule of thumb, each cup of tea/instant coffee or Americano needs roughly 200–250ml of near-boiling water.
| Peak-hour drinks | Approx. water needed | Recommended output | Typical venue |
|---|---|---|---|
| Up to 60 cups/hr | ~12–15L/hr | 30L/hr | Small café, office kitchen, kiosk |
| 60–150 cups/hr | ~15–30L/hr | 50L/hr | Busy café, bubble tea shop, staff canteen |
| 150–220 cups/hr | ~30–44L/hr | 60–70L/hr | Church hall, event catering, high-footfall coffee shop |
Buy a little above your calculated peak rather than exactly on it — a boiler running flat out with no headroom recovers slower as ambient water temperature drops in winter, and it gives you room to grow without replacing the unit next season.
Compare Keloo's autofill water boilers
| Model | Output | Tank | Format | Power | Price | Stock |
|---|---|---|---|---|---|---|
| 30L/Hr Wall-Mounted | 30L/hr | 6L | Wall-mounted | 3000W | £149.99 | In stock |
| 50L/Hr Freestanding | 50L/hr | 10L | Freestanding | 3000W | £149.99 | In stock |
| 50L/Hr Wall-Mounted | 50L/hr | 13L | Wall-mounted | 3000W | £179.99 | Check stock |
| 60L/Hr Freestanding | 60L/hr | 20L | Freestanding | 3000W | £179.99 | Check stock |
| 70L/Hr Freestanding | 70L/hr | 30L | Freestanding | 3000W | £199.99 | Check stock |
Stock levels change daily — the product page always shows current availability. The 50L/Hr Freestanding is Keloo's best-selling boiler by volume.
30L/Hr Wall-Mounted
£149.99
View product →
50L/Hr Freestanding
£149.99
View product →
50L/Hr Wall-Mounted
£179.99
View product →
60L/Hr Freestanding
£179.99
View product →
70L/Hr Freestanding
£199.99
View product →Find your size in 10 seconds
Plumbing, filtration & running costs
Installation
All Keloo autofill boilers need a cold mains water feed and a standard UK socket — no special wiring for the 3000W models. Wall-mounted units need a stud wall or bracket point capable of taking the filled weight; freestanding units just need worktop or floor space and clearance for the drip tray.
Water filtration
In hard-water areas (most of the UK), fit an inline scale filter ahead of the boiler. It's a £30–60 part that adds years to the element's life and keeps output consistent — scale build-up is the single biggest cause of a boiler's output figure quietly dropping over time.
Running costs
A 3000W boiler running at full output for an hour uses roughly 3kWh. In practice a boiler idles at a low holding wattage between draws, so real daily consumption is far lower than the rated power suggests — for most cafés it works out at a few pounds a week, not a day.
Frequently asked questions
Do I need a plumber to install an autofill water boiler?
Yes — autofill units connect to your cold mains supply, so a qualified plumber should make that connection (and ideally fit the inline filter at the same time). The electrical side is a standard UK plug for the 3000W models.
What's the difference between wall-mounted and freestanding boilers?
Both use the same autofill mechanism and heating element — the difference is purely footprint. Wall-mounted units free up worktop space but need a wall and bracket; freestanding units are quicker to install anywhere with a socket and a water line nearby.
How long does a 3000W boiler take to heat from cold?
Expect roughly 15–25 minutes for the full tank to reach temperature from a cold start, which is why most venues leave the boiler switched on for opening rather than powering it on and off through the day.
Can one boiler serve both a coffee machine and a tea/instant station?
A dedicated boiler is best kept for tea, instant coffee and general hot water — bean-to-cup and espresso machines have their own internal boilers built for the pressure and temperature stability espresso needs, so they shouldn't share a feed with your autofill unit.
Why is my boiler's output slower than the rated L/hr?
This is almost always limescale on the element. If output has dropped noticeably, descale the tank (or fit an inline filter if you haven't already) — a neglected element in a hard-water area can lose a third of its rated output within a year.
Compare the full range
Every Keloo boiler ships with a 12-month warranty and UK-based support.
Shop Commercial Water Boilers