View Question
Q: Energy consumption - Joules to Kilo Watts ( Answered,   5 Comments )
 Question
 Subject: Energy consumption - Joules to Kilo Watts Category: Science > Physics Asked by: domrep-ga List Price: \$5.00 Posted: 14 Oct 2004 08:43 PDT Expires: 13 Nov 2004 07:43 PST Question ID: 414788
 ```If I have a value of 220 mega joules per guest night consumption of a hotel room, how many kilo watts per guest night would that equel?```
 Subject: Re: Energy consumption - Joules to Kilo Watts Answered By: tar_heel_v-ga on 14 Oct 2004 09:02 PDT
 ```domrep... 1 megajoule is equivlant to 0.277777778 kilowatt hours, therefore, 220 megajoules per guestnight would be 61.11111111111 kilowatt hours. A kilowatt hour is one kilowatt of power being used over a period of one hour. So, you would be using 61 kilowatts per hour, per guest, per night. Thanks for your question. If you need any additional clarification, please let me know. Regards, -THV Search Strategy: convert kilowatt hours to kilowatt convert megajoules to kilowatt References: Mark Horrell - Energy Unit Converter http://www.markhorrell.com/tools/energy.asp Kilowatt-hour http://www.fact-index.com/k/ki/kilowatt_hour.html``` Request for Answer Clarification by domrep-ga on 14 Oct 2004 09:36 PDT ```We already had those numbers, thanks. What we are looking for is the kilo watt per guest night, not kilo watt hour. What is a "guest night" in terms of consumption? Is a guest night 8hrs, 6hrs etc? We know a standard exists, just don't know what it is :) Thanks, Robert.``` Clarification of Answer by tar_heel_v-ga on 14 Oct 2004 09:55 PDT ```A kilowatt hour is kilowatt used over an hour. Therefore, using the numbers you provided in your question, each night, you are using 61 kilowatts per hour, per room, per guest night if you are using 220 megajoules per guest night per room. Whatever standard for "guest night" you are using to get the megajoule number is the same standard you would use for the kilowatt conversion. If you are using 8 hours to arrive at the megajoule consumption rate, use 8 hours for the kilowatt consumption as well.``` Request for Answer Clarification by domrep-ga on 14 Oct 2004 10:28 PDT ```This is the problem! What is a "per guest night"? 8hrs, 6hrs etc? A standard exists for "per guest night" when you are talking about energy consumption. What is the standard, this is the question?``` Clarification of Answer by tar_heel_v-ga on 14 Oct 2004 13:22 PDT ```domrep.. My answer is based upon your original question and is correct. Your clarification request is another question, entirely different from your original question. I would suggest you post the question "A standard exists for "per guest night" when you are talking about energy consumption. What is the standard?" as a separate question. -THV```
 Subject: Re: Energy consumption - Joules to Kilo Watts From: hfshaw-ga on 14 Oct 2004 11:44 PDT
 ```Watts (W) and kilowatts (KW) are units that describe the consumption *rate* of energy, while KW-hrs (or Joules, or BTU's) describe the *amount* of energy consumed. Your request for an answer in terms of KW/guest night (or, as you seem to want, KW/hr) therefore doesn't make much sense. Perhaps if you described why you want this information, someone could help you better. Consider an analogy in terms of water use. KW would be equivalent to gallons of water per minute, while KW-hr is equivalent to gallons. Why would you want to know gallons of water used per minute per hour? Most comparisons of the energy efficiency of hotels are done in terms of either energy use per square foot (i.e., KW-hr/(sq. ft.)) or per occupant (KW-hr/person-night). You can see how the energy useage of your building (not limited to just hotels) at http://poet.lbl.gov/arch/. Comparisons are done for properties in the same general geographical area (via zip code), so a building in Juneau doesn't get compared to one in San Diego!```
 Subject: Re: Energy consumption - Joules to Kilo Watts From: racecar-ga on 14 Oct 2004 12:04 PDT
 ```Tar_heel: you did the calculation right, but your interpretation is wrong. You are correct that 220 mJ is 61 kWh. But it is NOT true that this means 61 kilowatts per hour. If guests use 220 mJ per night, then they use 61 kWh per night. There are various ways they could do this; here are a couple examples: they could use 61 kW for one hour (but not 61 kW per hour all night--that would be more than 61 kWh), or they could use 1 kW for 61 hours (if there were 61 hours in a night). domrep-- I have no idea what the standard is for hours per guest night. But if it's 8 hours, then the energy consumption rate per guest is 7.6 kilowatts. If it's 6 hours, then the rate is 10.2 kilowatts.```
 Subject: Re: Energy consumption - Joules to Kilo Watts From: hfshaw-ga on 14 Oct 2004 13:57 PDT
 ```Let be be somewhat inflamatory and say that when trying to understand the energy efficiency of a hotel operation, the actual number of hours that constitute a "guest night" is irrelevant. The energy per guest night figure is simply telling you how much energy it takes to support one guest that ties up a room for an entire 24 hour period. The way a number like 220MJ/guest-night is normally calculated is by taking the total energy useage of a property over a given period of time, and dividing that number by the total number of "stays" in the hotel during that period of time (one person staying for one day = one person-night). The total energy used includes a "fixed" amount that does not depend on the occupancy rate (i.e., the energy used to light and heat common areas, light the signs and grounds, run the reception, power the pool, etc.), and an amount that depends on the number of guests present (washing dirty towels and sheets, hot water useage, room lighting, HVAC energy if not a central system, vacuuming rooms that have been occupied, etc.)```
 Subject: Re: Energy consumption - Joules to Kilo Watts From: tar_heel_v-ga on 14 Oct 2004 14:00 PDT
 ```racecar.. You are completely correct in your comment. In reviewing my answer, I realize I mistype 61kW per hour when it should have been 61kWh per night. Thank you. -THV```
 Subject: Re: Energy consumption - Joules to Kilo Watts From: hedgie-ga on 14 Oct 2004 20:20 PDT
 ```Besides that, beside racecars comment, 'guest night' has two meanings. In UK it means night you can bring guests, in hotel industry it has to do with occupancy (number of guest nights per year). My guess is that asker, when saying " What we are looking for is the kilo watt per guest night, not kilo watt hour " exhibits the usual confusion between power and energy. There is an average consumption per night (occupied room) and that, of course is measured in in kWh or Joules, not in kW. Even if we would know 'how many hours' guest stays (awake?) the average rate of energy consumption would be fairly meanigless number. It can be defined, but I doubt there is a standard like that.```