I have now had the opportunity to check an electricity bill against the information published by ΔΕΗ. In case it helps anybody, here is the analysis.
Firstly the links on the UK version of the web site are not correct so it is necessary to use the Greek links. This is no big loss since the links on the English pages go to Greek tables. Use http://www.dei.gr/Default.aspx?id=30818&nt=19&lang=1
The first link is for normal domestic electricity and the second is for off-peak if you have it. I do so I have included it in the explanation below. Just ignore those bits if you don’t have it.
The first calculations at the top of the back page of the bill are for the electricity consumed. These agree with the figures given on the ΔΕΗ tables. In my case I have a fixed charge of €4.80 because I have three phase supply. This would be €1.52 if you have single phase. Next I consumed normal rate electricity of between 801 and 2000 kWh so that consumption is multiplied by 0.0946 €/kWh in accordance with the normal rate table. Next there is a fixed charge of €2 for having night rate electricity and the units consumed at night rate are then multiplied by 0.0661 €/kWh, both in accordance with the night rate table.
The next calculations are the additional costs. These are a little bit complicated since they involve elements that depend on the amount of electricity consumed and elements that depend on the rating of the supply. The latter are quoted in the tables per year so need to be factored for the period covered. This is the sum of the number of days covered by this bill plus the number covered by the previous intermediate bill all divided by 365. You can get the relevant number of days from the council tax calculation. All the information is on the night table where the normal rate figures are repeated and night rate figures added. The following is my case:
ΜΕΤΑΦΟΡΑΣ and ΔΙΑΝΟΜΗΣ are both calculated in the same way and only depend on the normal consumption, i.e. the night rates for these costs are all zero. They also depend on the rating of the supply, however, so the calculation has to be done in two stages. First take the figure in the €/kVA column, e.g. 0.17 in the case of ΜΕΤΑΦΟΡΑΣ, and multiply it by the kVA rating of your supply. This is given in the bottom left hand cell of the table with the actual meter readings at the top left of the bill. Then multiply this figure by the period factor. Next take the kWh consumed at normal rate and multiply it by the figure in the €/kWh column, e.g. 0.00541 in the case of ΜΕΤΑΦΟΡΑΣ. Add the two numbers together and the result should be pretty close to the figure given on the bill. In my case they differ by 10 cents. Repeat the above calculation using the figures given in the ΔΙΑΝΟΜΗΣ section of the ΔΕΗ table. This should be close to the figure on the bill. In my case they differed by about 15 cents. I cannot account for these small differences but it is possible that the number of days used by ΔΕΗ may be slightly different from those to calculate the council tax.
ΩΦΕΛΕΙΑΣ and ΛΟΙΠΕΣ are only calculated from the kWh consumed. In the case of ΛΟΙΠΕΣ there is a single rate so simply multiply this rate, i.e. 0.00046 by the total kWh consumed. For ΩΦΕΛΕΙΑΣ take the normal kWh consumed and multiply it by the €/kWh rate appropriate for the band in which that number of kWh falls. Then multiply the night electricity consumed by the €/kWh figure in the night part of the table. Add these two results together. These figures agreed exactly on my bill.
There is a final calculation, which I think is for pollution, but the details of that are shown on the bill.
Hope this helps.