Why do we use so much energy

michaels · 19 October 2017 at 5:12PM

Compared to many on here we are energy hogs. What I am trying to figure out is whether that just reflects our usage or whether there is 'something up' with our house and or appliances.

Does anyone have any suggestions of good sites which would let us work out what our usage should be given our lifestyle?

Some frightening figures - our usage is about 230kwh per sqm per year, this excludes EV charging. GCH with a conventional condensing boiler and modern mains pressure hw tank.

Our house is a 5 bed extended semi that is supposedly EPC B (brought up from C by the PV). Our boiler is 5 years old state of the art German model with weather compensation controls. We are pretty much fully LED. WE have 5 in the house and make normal use of lighting and electronics, cooking is all electric. Heating we heat 24/7 to 21-22C in the day (6AM - 11PM) and with a night min of 17C. We are pretty keen bathers with at least 8 showers and a bath every day.

Ectophile · 19 October 2017 at 7:52PM

Five people have 8 showers and a bath in one day? I think that might be the answer.

michaels · 19 October 2017 at 10:11PM

Yup, I am the dirty one who generally only bathes once a day.

I am looking for a website that lists likely useage by appliance and how much space and water heating should require in kwh.

silverwhistle · 19 October 2017 at 10:24PM

michaels wrote: »

Yup, I am the dirty one who generally only bathes once a day..

I was going to make a joke about that by you got in first. But I think Ectophile could be right..

I'm retired and if I'm not going out in the day I may only have a hygiene wash in the morning. A quick shower later or a hot bath like tonight after footie training (particularly given the appalling weather.

As I'm on my own apart from visitors and entertaining it's worth me being on a zero SC tariff. I import ~1100/600 (elec/gas). Couldn't tell you the usage per sq.m though.

michaels · 19 October 2017 at 10:55PM

So any tips on how to work out how much energy each bath and shower needs? I can compare monthly gas use in summer and winter although need to adjust for the pc diverter replacing some gas in the summer.

This suggests that hot water may be 1300kwh per month in summer, not sure about cold water temperature and whether seasonal dofferences in this are important (I guess average increase from 15 to 40 in summer would need 40% more in winter if it were 5 to 40 would suggest using an average of 20% more). This gives about 19000 owh per year for hot water and 13000 for space heating.

Now I need some data to see how this compares to other houses of a similar size and water usage.

pinnks · 19 October 2017 at 11:00PM

That does seem a lot. Even in the bad old, bad old, days of 30 year-old boiler, CRT TVs, 4 people and 3 2m high fridge-freezers we were at 200kWh per square meter. Now, albeit just 2 of us, we are about 90, ignoring own generation. New boiler, LED TVs, 3 fridges and freezers still but all A+++ and new A++ other appliances, LED lighting throughout and generally more energy conscious.

michaels · 19 October 2017 at 11:20PM

By my maths 19000kwh should be enough to heat 1200l per day from 10c to 40c at 80% efficiency - can anyone comfirm this?

Then if we say 150l for the bath and say another 50l of general hw use that means the showers use 125l each which is too high so is there an efficiency issue? I know modern condensing boilers are supposedly about 90% efficient but does anyone know how much of the energy supplied actually makes it to the tap (our tank is new and supposedly low loss and the pipes are lagged where visible).

Martyn1981 · 20 October 2017 at 7:25AM

michaels wrote: »

By my maths 19000kwh should be enough to heat 1200l per day from 10c to 40c at 80% efficiency - can anyone comfirm this?

Hiya, the maths looks fine, but perhaps there is something wrong in the assumptions?

Whilst there are only 2 of us here, our gas consumption during the non-heating months is only about 150kWh, perhaps 2,000kWh pa. But I should point out the oven is gas, but the hobs are leccy.

Maybe I should shower more often?

BTW, total gas consumption pa is about 7 to 8,000kWh.

Nick_C · 20 October 2017 at 8:13AM

Why are you heading your home to 17C overnight? I would suggest 7C from 1 hour before going to bed until two hours before getting up.

21 is also rather high for the middle of the day unless you are completely inactive

Is your hot water on constantly? Can you schedule it? Is your hot water tank thermostat (of you have one) set too high? Is your boiler temp set for Eco mode?

michaels · 20 October 2017 at 8:47AM

Our kids tend to cough at night if it gets cold and yes mostly when I am at home I am sitting down.

The hot water is set at 50 in the summer to give scope for the iboost divertor and 60 in the winter. Isn't there a risk of legionalla if you have cooler than this? Although I know the latter may mean the boiler operates outside comdensing range. The tank itself is modern and has a claimed miniscule u value but perhaps their are losses in the pipes especially where they are in the walls? We tend to have a wide range of shower times - say 5am to 10am and 7pm to 10pm so make sure the water is hot for both these periods.

Anyone any thoughts on whether the space heating usage sounds reasonable given the demand?

ASavvyBuyer · 20 October 2017 at 9:43AM

michaels wrote: »

Heating we heat 24/7 to 21-22C in the day (6AM - 11PM) and with a night min of 17C..

This may be one of the reasons why consumption is so high, Why 17C at night when you are tucked up in bed? 14C or 15C would be fine if you are under a duvet.

Also, during the day, for an active family, 18 - 20C should be plenty warm enough.

Why do we use so much energy

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