What Size Hot Water Boiler Does a Café or Office Need?

Start with cups in your busiest hour

A boiler that copes at 3pm can run dry at 10.30am. Count the tea, instant coffee, hot chocolate and americano top-ups you serve in your busiest hour, then turn that into litres.

Cups in the busiest hour	Hot water needed	Boiler class to look at
Up to 20	Up to 5 litres	Compact 3 to 6 litre boiler
20 to 40	5 to 10 litres	7 to 12 litre boiler
40 to 80	10 to 20 litres	13 to 21 litre boiler
80 or more	20 litres or more	21 litre boiler with a 3 kW element, or an undercounter system — ask us to size it

Assumptions: 250ml of hot water per cup (four cups per litre). A large mug takes more, an americano top-up less. Litres are the hour's total; the tank does not have to hold all of it, as the next section explains.

Tank size and recovery rate: the two numbers that matter

A boiler has two limits. The tank (sometimes listed as rapid draw-off) is how much ready-to-pour water you can take before it runs cool. The element, in kW, sets how fast that heat is replaced. The tank handles the rush; the element handles the hour.

Recovery can be worked out. Heating one litre from about 10°C to 95°C takes roughly 0.1 kWh, so a 1 kW element can bring up around 10 litres an hour before heat losses. Plan on about 9 litres an hour per kW: the manufacturer figures on our Instanta 1500 POU page (3 kW, 27 litres an hour, 11 litre draw-off) and Instanta 1000c page (2.25 kW, 20 litres an hour, 3 litre draw-off) sit on that line.

So: match the tank to your busiest 20 minutes and the kW to your busiest hour. A 7.5 litre tank with a 2.6 kW element pours 7.5 litres straight away, then keeps up with roughly 23 litres an hour, which is why a mid-size boiler copes with far more than its tank suggests when demand is spread out.

Which boiler size for which business

Tank and element figures from the product pages in our hot water boilers and dispensers range, with the kind of site each suits. All plumb into the mains.

Boiler	Tank or draw-off	Element	Typical fit
Instanta 1000c	3 litres (20 litres an hour)	2.25 kW, 13 amp plug	Small office kitchen or reception, steady trickle of drinks
Bravilor HWA 8	7.5 litres	2.6 kW	Office of 40 to 60 staff, café tea and americano station
Instanta 1500 POU	11 litres (27 litres an hour)	3 kW	Busy café counter, staff canteen
Bravilor HWA 12	12 litres	2.6 kW	Café or office with a sharp mid-morning peak
Bravilor HWA 14	14 litres	3.1 kW	Care home tea rounds, large office floor
Bravilor HWA 21	21 litres	3.1 kW	Canteens, event catering, 60-cup rounds

Figures are the manufacturers' statements as shown on our product pages on 4 November 2026. "Typical fit" applies the 250ml-a-cup rule: 20 cups = 5 litres, 40 = 10, 60 = 15. Worked examples: an office of 60 people on two hot drinks a day each makes 120 drinks; if half come from the boiler and 40% of those fall in the busiest hour, that is 24 cups, or 6 litres, so a 7.5 litre tank. A care home tea round of 60 cups in 30 minutes draws 15 litres faster than any element can replace it, so the tank itself must be 14 to 21 litres.

Plumbing, power and water: check these before you order

Plumbing. Every boiler above connects to a cold mains supply with an isolating valve and refills itself. Check there is a feed within reach of the worktop; our installation team can fit one if not.

Power. The two Instanta models come with a 13 amp plug, and a 2.6 kW element at 230 V draws about 11 amps, within a standard socket. A 3.1 kW element draws about 13.5 amps, above a 13 amp plug's rating, so the HWA 14 and HWA 21 may need a dedicated supply. Ask your electrician, or ask us when you order.

Water. A boiler holds water near boiling all day, which is exactly how limescale forms. In a hard-water area fit a water filter on the feed and keep a descaler to hand; our servicing page covers planned maintenance.

Do you still need a boiler alongside a coffee machine?

Usually, yes. A bean-to-cup machine makes coffee, not tea, and its hot water outlet is sized for the odd americano rather than a tea round; our guide to sizing a bean-to-cup machine for an office covers the coffee side. On an espresso bar, drawing americano water from the machine during a rush takes steam and recovery from the group heads; a separate boiler lifts that load. A filter or bulk brew machine handles jugs of coffee for meetings, but the tea and hot chocolate still come from the boiler.

Hot water boiler FAQs

How many cups of tea does a 10 litre boiler make?

About 40 cups of 250ml from the tank before it has to recover. A 2.6 kW element then adds roughly 23 litres an hour, so it keeps up with a steady 40 cups an hour or more.

Does a commercial water boiler need to be plumbed in?

The boilers in this guide all connect to a cold mains supply and refill themselves. Manual-fill urns exist, but for a site serving hot drinks all day a plumbed boiler saves staff time and cannot run dry.

Can I run a water boiler from a normal plug socket?

Models up to 2.6 kW draw about 11 amps at 230 V, so they run from a standard 13 amp socket, and the Instanta models come with a plug fitted. The 3.1 kW models draw around 13.5 amps, so they may need a dedicated supply; check with your electrician before ordering.

Do I need a water filter on a hot water boiler?

In a hard-water area, yes. Scale builds fastest in water held near boiling, and a filter on the feed plus a regular descale is far cheaper than a replacement element.