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How I can calculate or find a value for the start-up cost of a natural gas boiler? The boiler will have a capacity of about 700 kW and is intended for heating the water for a greenhouse.

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For accurate cost estimation you will need to find a vendor and have them supply you a "budgetary quote" for your 700 kW boiler. The vendor can usually get this type of quote to you more quickly than a firm quote because they are not held to that price or terms; though I find that frequently the price is the same when we go to purchase.

When I need an estimate in the next 10 minutes I try to find something on the internet with a price that I can scale. I find a unit closest to the type and capacity I need. Usually economy of scale ensures that I over estimate, but it doesnt hurt to give yourself some safety factor.

574,000 BTU Boiler for 14,000USD
700 kW is 2,390,000 BTU
2,390,000 BTU / 574,000 BTU = 4.16
4.16 * 14,000 USD = 58,240 USD
58,240 USD * 1.2 safety factor = 70,000 USD

Obviously you will have to do this for all your major components, piping, etc.

For installation costs you typically estimate some number of labor hours and multiply by your "shop rate." Accounting should be able to give you this number as it factors in all employee costs like benefits, vacation, training, tool overhead costs, etc.

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  • $\begingroup$ Thank you very much for your detailed answer. With start up cost I refer to the costs which are incurred in the transition to the steady state, etc. fuel costs during the starting up of a boiler which before had turned off. $\endgroup$ – user5026 Jan 11 '17 at 8:29
  • $\begingroup$ Gotcha. In that case your are basically looking for an efficiency calculation. Since this will vary greatly by boiler design and quality you will need to measure it empirically. Kw of heat out/ Kw of gas input = efficiency. Lets say you calculate it at 1 minute and 5 minutes from start. For 0 to 1 minute you multiply 1 minute x (1 - efficency) x gas flow. For 1 to 5 minutes you multiply 4 minutes x (1 - (efficency@1+efficency@5) /2) x gas flow. Add these two together and it will give you wasted gas during startup. Multiply that by your cost per volume of gas. Make sure to watch your units. $\endgroup$ – ericnutsch Jan 12 '17 at 16:38

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