Formula for Calculation increase in Gas bill

[Bronte]

Question 1
If the price of gas has gone from 4.509 per unit (kWh) to 5.471, plus the standing charge has increased from 13.7 per day to 14.3 and bearing in mind that VAT at 13.5 will be charged on it how much has the actual bill gone up by. If some one could do this with say 100 units and show the matematical formula for how it's calculated please.

Question 2
The bill increased on 1st September and it was an estimated bill. How did they decide how many units were to be calculated at the new higher rate?

Question 3
I have a booklet that gives 3 options on how I can be charged (never got this before) but it's standard tariff, no standing tariff and winter saver tariff. How can I tell which is the cheaper option (I only want the cheaper option). Does it depend on how much you use, as in the more units the cheaper it is?

Sorry I'd like to correct the title but it won't allow me to.

 

[gipimann]

In relation to Q3, there is a useful tariff calculator on the Bord Gais website, where you enter your kwh usage and it calculates the cost on each tariff so you can see which is cheapest.

www.bordgaisenergysupply.ie

edit: [broken link removed] a direct link to the tariff calculator page

 

[Bronte]

Thanks gipimann, I rang Bord Gais and they said there is no diffence in the tarriff's but I'll check out the calculator to double check.

Anyone have the mathematical formula for the percentage increase? Could I do it in excel?

 

[deadlyduck]

To calculate the additional cost of the various price increases, use the following logic:

((New unit price minus old unit price) x Number of units) + (New daily standing charge minus old daily standing charge) x Number of days