Energy Efficiency and sqft areas confusion

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Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Wed Jul 10, 2013 6:39 pm

I've cloud based energy monitors installed and am monitoring data of my apartment since last 8-9 months. My apartment is west facing top floor and used to heat up a lot, resulting in higher energy consumption. I had an energy consumption of 6300 Kwh/yr last year, after which I've taken up numerous measures which includes thermal sealing, retiring old appliances etc. This year my consumption for 6 mths is 1450 kwh.

My question was, I've seen various energy efficiency & green building organisations referring energy efficiency as KwH/sqft/year. I'm not sure which figure should I take for the square footage. If I take the carpet area (915sqft) then from 6.85 kwh/sqft/y last year I'm now on 3.16 kwh/sqft/y (projected this year).

I also wanted to know what is the kwh.sqft/y one needs to achieve to be labeled as energy efficient home. I read somewhere it was < 2.9 which includes heating & cooling. If the sqft is on bultup area I might have already achieved it, obviously there is always scope for improvement.


thanks,
Vineet
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Re: Energy Efficiency and sqft areas confusion

Postby Gordon-Loomberah » Wed Jul 10, 2013 7:02 pm

It sounds like you have halved your energy consumption, which is a good improvement! How much energy a house uses for heating and cooling is going to vary considerably with the climate. A vastly greater amount of insulation will be required to acheive the same energy use per area in say an arctic location than a temperate one.

I can see one source of confusion though- your mixed units! Have you thought about using BTUs per square metre instead ;)

kWh/m^2 would be best.
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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Wed Jul 10, 2013 7:38 pm

I think one would use BTU to calculate heat energy.

kwh/sqm/y can also be used instead of sqft, depends on which country one is and the prevalent unit of measurement.

50% > saving is surely good, but I want to be categorized as an energy efficient home as per given standards. This will give me a big morale boost. :geek:
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Re: Energy Efficiency and sqft areas confusion

Postby FarmerJohn » Thu Jul 11, 2013 8:01 am

vbhoj74 wrote:This will give me a big morale boost. :geek:


I simply derive my satisfaction from reduced energy bills :)
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Re: Energy Efficiency and sqft areas confusion

Postby davidg » Thu Jul 11, 2013 8:39 am

FarmerJohn wrote:I simply derive my satisfaction from reduced energy bills :)

Yes, in the future the way the AS4777.1 is going you will be unable to improve your solar setup unless your off-grid. At least the distributors of power (pun intended) can't control that yet :x
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Re: Energy Efficiency and sqft areas confusion

Postby Benny » Sun Jul 14, 2013 3:19 pm

Vineet - you can get some information on what you are looking for here ...
http://www.cvconstructions.com.au/Energy.html

Lots of other places you can read about house star rating and energy consumption.
You will see from the article that the level at which a house is rated as energy efficient ( say 6 star) depends on the local climate. Basically a place that is very hot or very cold will use more energy than somewhere that is very mild. Where are you ?
As an example, in Adelaide, they say 96MJ/sqm will classify as 6 star. 1kWh = 3.6MJ, so this is 27kWh/sqm, which is about 3kWh/sqft. This is close to what you are using. The area of the building is the whole building I imagine - why would you only use the "carpet area" ? Why exclude bathroom etc ?
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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Sun Jul 14, 2013 4:22 pm

Thanks Benny for a great heads up.

I'm in Kolkata, India, a hot and humid climate with 9 months of summers going to max 37 deg C and 3 months of winters hitting min 8 degs C. We don't yet have a govt promoted star rating for homes, we do have LEEDs for larger homes which does not apply to my apartment.

I went through that link you provided, and understood that 3 kwh/sqft/yr is when you maintain temp between 18 to 26 degs, which we don't. With no central cooling or heating, we have all split ACs and no heating since we are in a cooling dominated climate. We also use the cooling only when it is uncomfortable, before proper insulation those days were more. I also now believe that it is difficult to relate to other standards because of climate differences, maybe I'll have to look for a climate zone that closely matches ours for comparision.

It may sound mean, but with no bad intensions, I can probably still take comfort in comparing a friends energy usage who has a similar sized roof apartment as mine with no thermal sealing or any other energy efficiency measures, runs 5 to 7 times my present consumption.

Having said all of that, I still do not have a conclusive direction in the absence of a standard in my area or country, I do not know if I still need to work on the efficiency or I did enough. This is because even though my consumption is at least half than similar other homes, still it largely varies on personal usage.
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Re: Energy Efficiency and sqft areas confusion

Postby Benny » Mon Jul 15, 2013 12:22 pm

No problem Vineet. I think you're doing a great job and I hope you are telling your friends how much you are saving so that they can take action too. Some people here in Australia like to point to India and China as causing all the problem with CO2 emissions simply because they have such big populations, but we in Australia are much worse on a personal level and need to do a lot better.
It sounds like you have a climate more like Darwin in our far north. You can see more detailed information on the Nather web site here http://nathers.gov.au. Also they show that Darwin in fact is allowed much higher energy usage than Adelaide for a 6 star rating - as you say for the high cooling loads in summer. Darwin is rated at 349MJ/sqm/yr which is 96kWh/sqm and about 10kWh/sqft (please tell me that India has gone metric and we can forget the sqft (-; ) So you are performing at about the 10star level already !! As you say this is critically dependent on the temp you are willing to tolerate. We use a ball park figure that every 1degC increase in the thermostat (when cooling) will save 10% of the energy used.
You can also save energy by making sure you have a very high performance split system AC. Do you have star ratings on your appliances ? You can see how our appliances are rated here ... http://reg.energyrating.gov.au/comparat ... 64/search/
And if you look at the ratio of output to input power you can see that the best AC's have a ratio of about 5.
By the way, out of interest what do you pay for electricity over there ? WE pay about 25c/kWh which I think is about 14rupees/kWh.
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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Mon Jul 15, 2013 4:45 pm

Benny, sadly the awareness among people is very low, in fact to be honest, I myself got aware when I was struck with a huge energy bill last year, still it is a huge task to convince someone for capex investment and reap on opex. Out of 5 friends that I spoke to, 1 was willing to take a step forward, 1 appreciated, rest 3 debated says what's the point on expending so much.

If the planet is not conducive for habitat, there is no India, Australia or China. So I believe that we as human being should all work together across boundaries in partnership to save our planet for our children. I don't know why some ppl laugh at this thought, the sooner they understand the better all of us are.

I can follow both metric & US systems, in India we generally follow the sqft system for properties, height in ft, but Kg for weight, so we are kind of mixed economy. :-)

I'll check on Darwin and how it compares to our climate, more on that later, never been to that side, have made couple of family trips to the gold coast which seems to be have awesome weather all round.

and EER (w/w) of 5 ? wow ! I checked your link, in the first glance since I cannot sort the list on EER I was not able to locate anything around 5. We have splits of max EER of 3.7 from Sharp, I went for Panasonic 12PKY models which has EER of 3.47 if I remember correctly, which is 5 star rated here. This model has econavi. I had 2 window AC of Hitachi of 1.5T, sold them both, bought 1T + 1T + .75T, so I actually added air conditioned space.

Had a 7 yr old 300L samsung fridge, sold that too, and went for Pana Nr-bw465xsx3, which is 465L with econavi. So added on the refrigeration capacity too.

Our energy costs starts from .12 AUD cents (Rs 6.50) and can go upto .19 in residential areas based on slabs & usage. I have a custom made code running with my energy monitors which reply to mails with present billing cycle (3 months) data and compares with last yr. The energy monitors are from owlintuition (UK) and are like tongs which are non-intrusion based, i.e. one does not need to cut wires to install them, but it shows an added 12% usage, so we need to reduce the calculations by 12% approx. I'll PM you the details on how you can send the mail and receive the data back, would love your inputs on the same.
Last edited by vbhoj74 on Mon Jul 15, 2013 6:29 pm, edited 1 time in total.
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Re: Energy Efficiency and sqft areas confusion

Postby Gordon-Loomberah » Mon Jul 15, 2013 5:40 pm

Vineet, you will only find the higher EER/COPs on smaller units. I have a couple of 2.5kW Mitsubishis here that are close to EER/COP 5, but with larger units in the 4-5kW range you generally wont see any above 4, and it's even worse for larger 10+kW units.

See here:
http://reg.energyrating.gov.au/comparat ... ction=desc
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