Thermal Power

It depends on how long you want to take to produce the ton of steam.

Hospital uses two New 12 ton (presumably per hour) High Efficiency Garioni Naval Steam Boilers, gas fired. Thermal energy required is needed to estimate different modes of heat generation (electrical,solar, coal).

I don't know all the parameters here, and I'm not that much of a steamer in the first place. However, depending on the details of pressure, it takes about 1000 Btu/lb to boil water. You have to get it from supply temperature to boiling, and there may be some superheat added after, so for round numbers let's say 1200 Btu/lb. For each boiler, (12 tons x 2000 lb x 1200 Btu)/h = 28,800,000 Btu/h. One watt ≈ 3.41 Btu/h; thus 28,800,000/3.41 ≈ 8,445,749 W ≈ 8446 KW ≈ 8.45 MW. Two such boilers, 16.9 MW. If "ton" is supposed to be "metric ton", multiply by 1.1.

That seems like a lot, but I don't know what a hospital might need.... In any case those are only rough guesstimates.

[28,800,000/34,075(?) ≈ 845 boiler HP each. Yeah, that's pretty big. Largest boiler I've ever been around is about 300 HP.]

Thanks Tornado, that is exactly what I was looking for. That is thermal power that we are talking about? Efficiency of converting other forms of energy to heat needs to be accounted for (electricity, coal, solar etc.)

I should mention an additional thing. Those thumbnail calcs represented the energy going into water --> steam. The fuel Btu will be more on account of waste energy up the stack. Thus there is another efficiency factor involved, but I forget what it is for various boilers. For an "apples to apples" comparison, we would need also to account for variations in efficiency among the proposed alternatives. My experience on those is too limited, but first things first, get into the ballpark....

It depends upon the starting temperature of the water.

→ Steam Tables.