LPG Water Heating Calculations

[mcmurphy]

Can someone please verify the following calculations for my hydronic heating.

The heating load is approx 45kw per hour

Using LPG as natural gas is not available:

I litre of LPG costs approx 74 cents.

Each litre of LPG equates to 25 Mj ?

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Physical Properties of LPG (Propane)


<table align="center" border="1" bordercolor="#ffffff" cellpadding="4" cellspacing="0"> <tbody> <tr> <td class="style13">Mj/litre of liquid</td> <td class="style13">=</td> <td class="style13">25.5 Mj/litre of vapour</td> </tr> <tr> <td class="style13">Mj/kg of liquid</td> <td class="style13">=</td> <td class="style13">50.4 Mj/kg of vapour</td> </tr> <tr> <td class="style13">Mj/m of vapour</td> <td class="style13">=</td> <td class="style13">96 Mj</td> </tr> <tr> <td class="style13">litres/tonne</td> <td class="style13">=</td> <td class="style13">1975 litres of liquid</td></tr></tbody></table>

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The boiler I am looking at is as follows:
www.simonsboiler.com.au/products/hot_water_boilers/Raypak/downloads/Model_200_280_350_430.pdf

This states:

Hourly Gas Input (MJ/hr):
LPG (Propane) 185

Hourly Energy Output (kW):
LPG (Propane) 41

So the cost of 45kw per hour would be:
($0.74/25) * 185 = $5.47


Anyone care to verify this... please

Thanks