Kilowatts to Boiler Horsepower for Process Steam Loads

Matching a Process Steam Load to a US Boiler Catalogue

The heat load schedule for a brewery, a laundry or a food plant arrives in kilowatts: so many for the kettle, so many for the CIP set, so many for the washer. Then the quotation comes back from a North American supplier and every model in it is listed in boiler horsepower. Before you can tell whether the 40 bhp unit is right or two sizes too small, the load has to be restated in the catalogue's own currency.

Conversion factor: 1 kW = 0.101941995 bhp — divide the kilowatt duty by 9.8095. A brewhouse boil drawing 300 kW is 30.58 bhp, which is why the 30 bhp boiler on the price list is already beaten by the load and the 40 bhp model is the honest choice.

What Makes Process Sizing Different from Heating Sizing

Loads are batches, not a steady draw

A kettle coming to the boil, a retort on its come-up, a washer starting a cycle: process steam arrives in short heavy blocks and then falls away, so the number that matters is the coincident peak, not the daily average.

Catalogues climb in fixed steps

Packaged boilers come in a familiar ladder — 15, 20, 30, 40, 50, 60, 80, 100 bhp — so a converted duty almost never lands on a model. Knowing where it falls between two steps is the whole decision.

Feedwater temperature moves the real output

A plant returning hot condensate gets far closer to the catalogue figure than one making up with cold town water, which is why the return rate belongs on the sizing sheet next to the kilowatts.

Room to grow costs less now than later

A step up in boiler size is a modest premium at the order stage; adding a second boiler and a second flue two years into production is not. Convert the planned line as well as the current one.

Working a Load Schedule into a Boiler Order

Take the schedule one user at a time, then deal with the total. The converter is quickest if you go line by line rather than trying to do the arithmetic in your head at the end.

Put each steam user's duty in as kilowatts

Enter 150 for the CIP set, 300 for the kettle, 500 for the tunnel washer. The bhp equivalent updates while you type, and spaces or a comma decimal separator in a pasted figure are handled without complaint.

Convert the coincident total, not the arithmetic total

Add only the users that genuinely run together, apply your diversity judgement, then convert that figure. Converting each line separately and summing the bhp gives the same answer — but converting an unrealistic total buys an unrealistic boiler.

Flip direction when the supplier answers in bhp

The swap button (↔) turns the page into bhp → kW, so a 60 bhp offer can be checked against your kilowatt schedule in one move rather than being re-entered.

Copy the plain figure onto the enquiry

Copy places the number alone on the clipboard, with no unit and no thousands spacing, ready for the sizing sheet or the specification you are sending out. Ctrl + C in a field does the same thing.

The converted figure is the duty, not the purchase: a load of 30.58 bhp does not mean a 30 bhp boiler will cover it. Once you have the number, round up to the next catalogue step and check the turndown at the bottom of your load range.

Process Steam Users and the Boiler Size They Point To

Representative steam duties from brewing, food and commercial laundry work, converted to boiler horsepower and set against the packaged size a single-user plant would order.

Steam user	Duty	In boiler horsepower	Nearest catalogue step
Steam press and finishing table	60 kW	6.12 bhp	15 bhp — the smallest packaged unit
Jacketed cooking kettle, 300 L	100 kW	10.19 bhp	15 bhp
CIP set, caustic heating	150 kW	15.29 bhp	20 bhp
HTST pasteuriser	250 kW	25.49 bhp	30 bhp
Brewhouse kettle at the boil, 20 bbl	300 kW	30.58 bhp	40 bhp
Retort, come-up and hold	400 kW	40.78 bhp	50 bhp
Tunnel washer, continuous batch	500 kW	50.97 bhp	60 bhp
Small brewery, coincident plant load	750 kW	76.46 bhp	80 bhp

Two things stand out. First, nothing lands on a catalogue size — every row rounds up, and the gap between the duty and the model you buy is real spare capacity you should be aware of rather than surprised by. Second, the bottom row is not the sum of the rows above it: a brewery running a kettle, a CIP set and a few smaller users does not fire them all at full duty in the same minute, and sizing on the arithmetic sum would land you two catalogue steps too high with a boiler that spends its life short-cycling.

What Helps When the Enquiry Is Being Written

Type a duty, read the boiler size beside it

The pair of fields updates on every keystroke, so a whole schedule of users can be walked through in one sitting without clearing or re-entering anything.

Turn a bhp offer back into schedule units

Suppliers reply in boiler horsepower; the swap arrows put their model straight back into the kilowatts your process engineers wrote the load in.

kcal/h and BTU/h duties from the same field

Older equipment data sheets quote heat in kcal/h and US ones in BTU/h. Both are in the searchable dropdown, so a mixed schedule needs only one page.

Numbers that paste into the sizing sheet

Up to eight decimals on screen with thousands spaced for legibility, and a copy button that strips it back to something a spreadsheet cell will accept.

Process Boiler Sizing Questions

Do I add up every steam user on the plant to get the boiler size?

Only the ones that can peak together. A brewery boils one kettle at a time and the CIP set usually runs after the brew, not during it; a laundry, by contrast, starts everything at seven in the morning and holds it there. Build a simple hour-by-hour picture of the shift, find the worst coincident hour, and convert that. Sizing on the arithmetic sum of every nameplate is the most common way plants end up with a boiler two steps too large.

How much does condensate return change the size I need?

A great deal. Returning condensate at 80–90 °C means the boiler only has to lift feedwater the last stretch to steam; making up with 10 °C town water means it lifts the whole way, and the same shell delivers noticeably less steam per hour. A plant with a good return rate can sit at the catalogue figure; one that dumps its condensate should assume roughly a tenth less real output, plus the water treatment and blowdown that come with constant fresh make-up.

Why do North American suppliers still list boilers in horsepower at all?

It is an inherited trade convention that stuck because the whole supply chain speaks it. Insurance inspection scopes, operator licensing thresholds in some states, feedwater and blowdown accessory sizing, even the way service companies price a call-out are all pegged to the bhp number. A supplier who relabelled the range in kilowatts would be the only one in the conversation using them, so the unit survives long after the reasoning behind it stopped mattering to the buyer.

What turndown should I ask for once I know the duty?

Compare the peak you converted with the quietest part of the day. A plant peaking at 50 bhp but idling at 5 bhp overnight needs about 10:1, which means a modulating burner rather than the on/off or high/low arrangement supplied as standard on small packages. Without it the boiler cycles on and off all night, wasting fuel on purge and pre-purge and putting thermal stress into the shell. Where a single burner cannot cover the range, two smaller boilers in lead–lag often beat one large one.

The peak only lasts ten minutes. Must the boiler cover it?

Not necessarily, and this is where a lot of money is saved. A short, predictable spike — a kettle come-up, a retort venting — can be ridden out by stored energy instead of installed capacity: a steam accumulator, a larger receiver, or simply staggering the batch start so it does not collide with the wash cycle. Convert both figures, the true peak and the sustained load, and put them side by side in the enquiry. A supplier can then quote against the load your plant actually has rather than against its worst ten minutes.

Kilowatts to Boiler Horsepower