Energy Diet

Due to technical aspects of this task, our today’s post will also be quite technical.

Efficient use of energy and potable water is the tradition in our family. The main energy source in our household is natural gas for heating, cooking and electricity. Of course, we shouldn’t forget both our cars, which use petrol as a propellant. Our awareness of the importance of permanent implementation of the efficient energy consumption comes from both ecological and economical reasons. Less energy consumption means lower costs – and accordingly, a reduction of pollution, which of course makes for a cleaner environment. It’s very similar also for potable water. We implement all of the above stated measures in the way in which we can still live a comfortable life.

The first step toward efficient energy consumption is its measurement and usage control. That’s the reason we have already (for two decades) kept records of the consumed natural gas, electric energy and water. Accounts received from energy and water suppliers don’t provide us with a sufficient means of control over the consumption volume, because the suppliers scan the actual consumption only a few times per year. With this kind of system, bills show us only average usage within a specified period. So, our own evidence helps us with the definition of our success.

Most energy in the house (natural gas) is used for heating and for hot sanitary water. The heating season in Ljubljana begins in October and ends in April. Usage of natural gas for heating, hot water and cooking for our house (200 m2) is around 2300 m3, which annually represents 110kWh/m2. This result is not bad for a house was built in 1985. Average usage of electricity annually is 5,000 kWh.

The volume of consumption of NATURAL GAS for heating, hot water and cooking:

YEAR 2008 YEAR 2009 YEAR 2010
JANUARY 448 560 432
FEBRUARY 387 357 372
MARCH 362 295 290
APRIL 181 97 147
MAJ 82 49 63
JUNE 65 41 43
JULY 64 40 36
AUGUST 63 45 40
SEPTEMBER 79 42 47
OCTOBER 136 115 148
NOVEMBER 285 224 237
DECEMBER 448 357 453
TOTAL: 2600 m3 2222 m3 2308 m3

The heating system was replaced in April 2009. From the volume of consumption it is apparent that the consumption on the annual level has decreased approximately 14% in years 2009 and 2010. In comparison with the year 2008, the reduction is evident from the table above. It is interesting that the consumption is significantly lower during the summer months. In December 2010 temperatures went significantly below average, but even with that, our consumption of natural gas was equal in the year 2008.

YEAR 2008 YEAR 2009 YEAR 2010
JANUARY 562 538 481
FEBRUARY 509 359 373
MARCH 506 476 429
APRIL 363 370 413
MAJ 344 417 407
JUNE 361 275 384
JULY 349 365 247
AUGUST 353 497 407
SEPTEMBER 444 386 373
OCTOBER 443 420 433
NOVEMBER 518 456 416
DECEMBER 528 509 545
TOTAL: 5280 kWh 5068 kWh 4908 kWh

Average usage of electricity is gradually decreasing year over year. In 2009 and 2010 we went on holidays in July, which is evident also from the electricity consumption. In August, the consumption was significantly higher because of cooling. Through the whole year, the consumption of electricity is much steadier in comparison to the consumption of natural gas.

YEAR 2008 YEAR 2009 YEAR 2010
JANUARY 15 15 14
FEBRUARY 14 11 11
MARCH 15 15 14
APRIL 13 14 13
MAJ 13 18 18
JUNE 15 16 11
JULY 11 10 13
AUGUST 13 17 10
SEPTEMBER 17 16 15
OCTOBER 14 16 17
NOVEMBER 16 14 11
DECEMBER 15 15 18
TOTAL: 171 m3 177 m3 165 m3


This task was quite easy and didn’t present us with any problems, since we had already been keeping track of this. By keeping our own records of energy and water consumption, we can compare the same months of different years. Anytime we want to determine our efficiency, it has to be considered that the average monthly temperature has a significant impact on energy consumption for heating.

Over 20 years of record-keeping, the volume of usable area in our house was changing, and with it, the scope of heating. So our measures of energy efficiency are not always evident when you consider this factor and the ambient temperature and heating surface. For the above stated years, though, the size of the heated space and the number of residents has been the same. On the upper floor, there are two adults and two children (Janez, Mateja, Tilen and Krištof) and on the lower floor there are two adults (mother in-law and father in law).

The gas consumption level of 2,300 m3 equates to 21,850 kWh — this is four times more than our electricity consumption (5,000 kWh) and represents the biggest part of energy consumption in our house. It would be interesting to calculate also the energy consumption which is the product of car driving. Fast calculation shows us that we make annually approximately 27,000 km by both cars, which represents more than 2100 liters of petrol. That means that our cars are in fact the biggest energy consumption in our household.


We can determine that with the energy consumption and the potable water consumption in our household we are quite efficient already. Nevertheless, it is possible to be even more consistent at an energy-efficient way of life, and in the near future, we could change the ordinary radiator valves with thermostatic and thus optimize the temperature in every single room. Greater savings would require additional investments for improving insulation of the building envelope and glazing. I believe that these technical measures of energy efficiency are not imperative until the necessary reconstruction will be needed because of the dilapidation. When we are calculating our energy footprint we also have to consider the energy footprint for production of the goods we are buying as well as the energy which is used by the product itself during its life cycle.


  1. Christina
    Washington, D.C.
    January 31, 2011, 12:40 pm

    I am blown away by the level of data you guys have and the way you have already made moves to be efficient. Kudos!

  2. clipton
    February 1, 2011, 12:29 pm

    Great analysis. As Yogesh said, if you cannot measure, you cannot improve. The best first step is mapping out energy consumption as done here. Other families reading this post would do a formidable first step to follow suit. I recommend tracing back the 24 previous months at least to give an insightful picture of energy consumption. If that is not possible, then try for the last year at least.

    Also, good thought about taking care of dilapidation issues first. One easy example is moisture. Moisture problems trump an efficiency problems. Since moisture contributes to an inordinately high percentage of building failures, it is imperative to address this before spending time and money on anything else.

  3. Dave Chameides
    February 3, 2011, 12:35 pm

    Fantastic. KNowledge of what you are doing is the best way to start improving and it looks as if you are well along the path on that front. Wish everyone did this!

  4. Mateja
    February 3, 2011, 3:57 pm

    Thx to all. It’s really encouraging to hear it 🙂