The conversion from BTU to Watt/Hour is 1 Kwatt/hour = 3.412 btu
As an exampe again I can tell you that my house is fitted with split type reverse heat pump air conditioners that are really quiet (around 32 db at full power) and to cool a room of 3,5x3,5 metres (132 sqfeet) we needed to install a unit with a power of 2500Wh (it is 8500btu) and on really hot days (outside temp of 40°C) we can't get less than 26°C even after more than an hour of contiuous operation, shame on the double glass window that is 2,5x2,8 metres...
Also in Italy it was common (a bit less now) to name pipes according to their size in inches. Actually, if you ask for a 19 mm pipe you could see printed on the pipe the mark 3/4 inch too.
The same is for air conditioners, you see 3 marks: "frigorie", the same as calories but for cooling, BTU and KW hour.
The use of non S.I. units is illegal since the 1973 I think and before the wide adoption of the S.I. units there was the c.g.s. system (centimetre, gram, second) system that is called "the engeneering system" and used similar units to the S.I. system but had many interesting variaton like in the definition of an Ampere ond the force being expressed in KGF (Kilograms force) rather than Newtons.
We have the same conversion for gas as the one Theo pointed out, corrected for zone and gas type/density. This month we had a correction coefficent of 1,03. The LHV is of 38MJ/cubic metre so it's not real methane in the pipes (that would have been 49,98MJ/cubic metre) .
I called my water company today and I've asked them about the heating, well... I couldn't expect anything worse, I waited for something like 5 minutes and the girl at the phone didn't know a thing. Hopefully I was able to call the administrator for our condo and this is what he told me:
it turns out that the heater plant is on the building next to mine, at number 24, just under a sport suppiles retailer and the heating is via gas that derives from gassification of biomaterial (garbage I believe) but I think that the thing runs on "standard" gas like my hobs and it claims to use "greener energy sources" only because there is a "green certificates" campaign. Like when you buy the right to burn fossil fuel if somebody else generates energy in a enviromentally safe way for you and sells you the green certificate of clean energy production. I hope that it is clear, it's becoming a real mess in the energy generation field because of these "green certificates" market.
And again I hope my Italian-English is clear enough for you to undestand, there'll never be enough proof reading!