Working out energy bills and direct debits

National_Numeracy · 29 November 2017 at 2:24PM

For money savers, the cost of heating your home is always a hot topic (pun intended). But for those with patchy maths skills, understanding the charges can be a bit of a nightmare.

At National Numeracy we want to help people understand the maths behind the charges, so we thought we'd ask for MSE users' help in explaining the numbers.

So, in that spirit - how would you work out the question below? What aspects of numeracy would you use to arrive at your conclusion?

If you use 11,650 kWh of gas a year, what is a sensible amount for a monthly direct debit?

Gas Tariff:
4.0p per kWh
Standing charge 22p/day

If you don't know where to start and you struggle with working out bills, then the National Numeracy Challenge could help. It's a confidential and informal website, where you can assess your numeracy, learn everyday maths, and work towards getting the Essentials of Numeracy. Register for free here.

Related on MoneySavingExpert: https://www.moneysavingexpert.com/cheapenergyclub

matelodave · 29 November 2017 at 2:55PM

11,650 kwh at 4p/kwh = £466 (multiplication)
365 days at 22p = £80.30 (multiplication)
Annual bill (466+80,30) = £546.30. (addition)

Divide that by 12 to give a monthly DD of £45.525 say £46 a month (division)

Nick_C · 29 November 2017 at 3:03PM

If only it was that easy though.

Your gas usage is probably shown in cubic meters. You need to use a conversion factor (constant) and then adjust for the calorific value (variable) before you get to your KWh usage.

I consider myself highly numerate, but estimating the annual cost of gas is far from straightforward. You need good skills as well if you want to do this on a spreadsheet.

Raxiel · 29 November 2017 at 3:16PM

matelodave wrote: »

11,650 kwh at 4p/kwh = £466 (multiplication)
365 days at 22p = £80.30 (multiplication)
Annual bill (466+80,30) = £546.30. (addition)

Divide that by 12 to give a monthly DD of £45.525 say £46 a month (division)

I don't normally make 'me too' posts, but that's how I'd calculate it too.

It's when you are trying to get from Volume of gas to monthly charge via kWh that things get... interesting.

Edit: Nick_C beat me to it, that'll teach me not to refresh before posting.

If I were planning ahead, I think I'd assume a flat CV of 40 as a slight overestimate compared to the average in my region.

I actually have such a spreadsheet here: https://docs.google.com/spreadsheets/d/1LsLIrx-lkdJ0FOrg3tSn2RB6a8k9_WUKYfXFExVWjIA/pub?output=xlsx

st999 · 29 November 2017 at 3:24PM

If only it was that easy though.
Your gas usage is probably shown in cubic meters. You need to use a conversion factor (constant) and then adjust for the calorific value (variable) before you get to your KWh usage.

I consider myself highly numerate, but estimating the annual cost of gas is far from straightforward. You need good skills as well if you want to do this on a spreadsheet.

But it is that easy, the conversion was already done for you.

I'm in my 70's and have no difficulty making a spreadsheet and working it out.

Nick_C · 29 November 2017 at 3:32PM

st999 wrote: »

But it is that easy, the conversion was already done for you.

I'm in my 70's and have no difficulty making a spreadsheet and working it out.

Yes, the conversion has been done for us, but in real life it is not that easy if you want to check your consumption has been calculated correctly.

In your 70s, I would expect you to be able to set up a spreadsheet to do this, as maths was taught properly in those days, and you will understand how orders of precedence apply within your formulae. I suffered being taught under the "School Mathematics Project" when I changed schools at 13. My Maths teacher told me to forget BODMAS and simply work from left to right!

I had many work colleagues who would not be able to set up a spreadsheet to work out a gas bill in an elegant manner.

System · 29 November 2017 at 3:43PM

Nick_C wrote: »

In your 70s, I would expect you to be able to set up a spreadsheet to do this,

Err no. More likely a drawn out table with computed figures worked out by using long multiplication; log tables or a slide rule.

matelodave · 29 November 2017 at 3:58PM

Hengus wrote: »

Err no. More likely a drawn out table with computed figures worked out by using long multiplication; log tables or a slide rule.

I'm in my 70's and so's my wife and we can both set up a spreadsheet (in fact she's better than me at it).

It's a long time since the old "guessing stick" (slide-rule) and log tables have been used although I do tend to use a calculator.

I'm actually horrified at the poor grasp of basic arithmetic of the youngsters nowadays but when I sit down with the grandkids I'm as baffled as they are with the way they are being tought.

They can get it almost the first time when shown the way we do it but it's taking weeks if not months to teach them at school.

Nick_C · 29 November 2017 at 4:15PM

I still have a slide rule but I'm blowed if I can remember how to use it.

I'd be OK with log tables though. In fact it would be nice to have some use for remembering the Log of Pi; one of the many bits of knowledge that I learned as a child which are now useless.

Raxiel · 29 November 2017 at 4:18PM

This thread got pretty alarming.

My kids are too young for school, guess I'll have to pay close attention to their maths homework once they're old enough to start getting it.

Ilona · 29 November 2017 at 4:37PM

I had to give it some thought to work it out, and check with matelodave to see if I was on the right track. I am 68, can't do spreadsheets, columns of numbers mean nothing to me. Maths was my worst subject at school, I have number blindness.

I don't use comparison sites because I don't understand them. I am with a company that charges the same rate for monthly DD and quarterly bills. I prefer to pay quarterly into the Post Office. They have no penalties for paying this way, and no standing charge. I keep my bills low by using gas and electricity frugally.

Ilona

Working out energy bills and direct debits

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