How to estimate consumption in a very large building

Badger_Lady

Hia,

Here's a challenge for ya! I've been googling the hell out of this but it doesn't seem to be easy...

I need to estimate how much electricity the following building might use:

- A former college with 8 floors (including G floor), approximately 10 classrooms (so large spaces) on each floor, plus one large communal space. Double glazed concrete with a flat roof.

- A total of 4 bathrooms (with 8 shower cubicles running constant hot water), and 7 kitchens.

- Each kitchen contains, on average:
-- 1 instant water heater over the sink
-- 1 washing machine
-- 3 fridges
-- 3 microwaves
-- 3 hot plates
-- 1 desktop cooker (there are NO full electric ovens)
-- 5 kettles

- No central heating or gas supply of any kind.

- A limited electrical system that includes:
-- Permanent lighting in the stairwells but none in the corridors.
-- Working light switches in each classroom and bathroom / kitchen.
-- Electrical sockets in every room.

- Roughly 100 adult occupants living in the building, sharing these facilities.

In the summer, this would be everything - we'll have to assume some variation between living habits, i.e. some will be at home all day while others will only be there 4 nights a week... some may use an iron or TV while others won't own either... however none are rich so their habits are likely to be reflected in their consumption.

In the winter, some of these occupants will be running oil-filled electric heaters - again, this will probably vary between heavy and light usage.

How the hell do I work out what the monthly bill might be?

daveyjp

£2-3,000 a week, including water rates.

Badger_Lady

Thanks Davey Is that summer, winter or an average over the course of 12 months?

Badger_Lady

daveyjp wrote: »

£2-3,000 a week, including water rates.

Really, I am interested in this calculation... I'd love to hear more!

In my 3-bed house, 3 adults share an electric bill of around £50 a month (averaged out across 12 months).

If you call that £12 a week, then each person is liable for £4 a week.

According to your post, each resident at the college, despite having fewer facilities or home comforts, would be liable for £30 a week.

Why such a huge difference?

Pincher

Badger_Lady wrote: »

According to your post, each resident at the college, despite having fewer facilities or home comforts, would be liable for £30 a week.

A proper gang master should know that you turn the water and electricity on once a day, if you are feeling generous. You have to turn off the tap water otherwise they won't buy your bottled water for £1 a pop. If you get triple bunks to pack more in, don't get cheap and forget the railings, they can die if they fall out at night from the top bunk: think about the paperwork.

rogerblack

Badger_Lady wrote: »

How the hell do I work out what the monthly bill might be?

You do a proper energy assessment!

This would include for example:
Work out the structure of the building. U values of all the elements - walls, windows, ceiling, floors.
Work out the desired temperature.
Work out the solar gain.

Now, taking into account the overall U value, and areas of the elements, compute how much energy it's going to need to heat and possibly cool, over the year.
It's probably reasonable as a ballpark to assume the building will be heated to a uniform temperature once some fraction of occupants are in it, so individual consumption is less important.

Then you go to working out the energy consumption of other appliances, remembering that if it's a day where heating is desired, you apportion some fraction of their output to heating.

For example, a TV or a microwave, all of the energy goes into heat.
A sink water heater, maybe 20%, as most of it will go down the drain.

Energy saving measures over the whole building are probably a good plan.
Fit either CFL, or linear fluorescent everywhere, rather than incan.
LED probably isn't quite there yet.
While expensive, a large heatpump may pay off moderately fast.
Also, considering stuff like combined heat and power.

On the initially expensive, but easy to fit front.
http://www.ebay.co.uk/itm/12000-BTU-WALL-SPLIT-CONDITIONING-UNIT-HEAT-PUMP-SYSTEM-/310207655543?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item4839d12e77 - for example - 400 quid gets you a 3.5kW output heater, which uses a kilowatt in.

Assuming in real life, it's more like 2.5*, compared to a 2kW oil filled radiator on for 80 days, you've saved 230 in electricity the first year.
In the second year, it's paid off. Any subsequent years it lasts is pure savings.
There are not much more expensive units with 5 year warranties.

Badger_Lady

Roger I love everything you've done there - thank you

Unfortunately though I don't have any power to change facilities in the building - the electric provision is what it is. I just don't know how much that is .

I also think it's fair to say that the building won't ever be heated 'uniformly' or to the same degree as a normal living residence would be... apart from anything else, the expansive corridors, stairwells and bathrooms will never have any sort of heating in them - any oil-filled radiators will almost certainly restricted to the 'classrooms' (bedrooms).

So how do I do this business with the U values an' that?

14Westfield

Is this a squat?!

Power/water rates for a former college will be at non-domestic tariffs and far more expensive what you would expect when comparing to a scaled up house. If planning etc has been granted to reclass as residential use then there will be large savings although probably large costs testing etc all the existing set up.
Also i'd imagine that the insulation/draft proofing for the building is in a poor condition as it was not designed to be used overnight.
you may find the electrics are laid out with a vertical 'tree' and each floor comes off from this central line. If it is you can clip on electricity meters to the floor level branches to get an idea of what each floor is using. Much of the appliance use will be down the occupant habits for heating/gadgets etc so would be best to be tracked so folks can pay more or use less ;-)

Badger_Lady

14Westfield wrote: »

Is this a squat?!

Yup. But it has been set up for residential use - we pay Council Tax etc

OK, so in the meantime I've Googled individual appliance usage against a normal domestic tariff, bundled them into a spreadsheet and added a bit extra for good measure.

My 'fag packet analysis' is:
Annual bill excluding heating: £18,766.24
Annual bill including 5 months of running oil-filled heaters: £49,791.24

So, in other words, £1,563.85 a month from March-September and £7,768.85 a month from October-February.

Does that sound completely off the wall??