Water Heating & Fuel Use Calculator

Use this calculator to work out how much heating power you need from your boiler, what outlet temperature you can achieve, and how much fuel your hot water pressure washer will use in real working conditions.

It is designed for UK contractors running diesel or kerosene-fired boilers on hot water pressure washers, van-mounted systems and softwash skids. Simply enter your flow rate, temperatures and fuel details to see an instant estimate of fuel consumption and running costs.

What this calculator can show you

• Required heating power in kW for your chosen flow and temperature rise.
• The outlet water temperature you can expect at a given kW and flow rate.
• The maximum flow rate you can run for a target outlet temperature.
• Estimated fuel consumption at 60% and 100% burner duty (litres per hour).
• Approximate cost per hour based on your fuel price per litre.
• Estimated working time per tank of fuel.

How to use it

1. Choose what you want to calculate: heating power, water temperature or flow rate.
2. Enter your inlet water temperature, the outlet temperature or flow rate you are aiming for, and the details of your boiler.
3. Add your fuel price per litre and the size of your fuel tank to see running costs and working time.
4. Click Calculate to see the results. Adjust the numbers to compare different setups (for example, higher flow vs higher temperature).

This tool is intended as a guide to help size hot water pressure washers and understand boiler fuel consumption in everyday exterior cleaning work. Actual performance will depend on the condition of your machine, burner efficiency and real-world operating conditions.