Hot Water - Gas usage = 0.7kWh or 10p per hour just to keep hot water hot when potentially not need, could you save this as well?

Posted 31st Aug 2022
3989137-jUZuS.jpg3989137-blQq7.jpgThis might we be useful to others, hence posting. This will vary given different boiler/hot water setups, but I had my hot water set to come on twice a day:
04:30-8:00 - I shower in the mornings
15:00-20:00 - My wife showers and Son has a bath in the evening

I have not changed these timings since I stopped working in London, when I used to shower at 5am, now typically 7am.

Looking at my smart meter/EDF energy hub, I noticed that typically each morning (4:30am) the boiler kicks in and heats the hot water, using 2.1kWh or at current rates 31p
Then each hour to keep this water hot, uses 0.7kWh or 10p each hour
After showering we use another 2.1kWh to heat the water again 31p

During the day we use very little hot water, pretty much only wash hands, etc. as our appliances (dishwasher) use cold water and heat it by electric.

At 15:00 when I forgot to turn off the hot water whilst away we used another 1.44kWh, which implies the water had lost most of the temperature between 08:00-15:00 and needs re-heating. Therefore my re-heat costs = 2 hour keep warm cost, for those keeping the hot water hot all day.

Where i am going with this is it costs me, with my setup, 10p per hour to keep water hot, when I have no requirements for that hot water.
Hence I have significantly reduced the hot water "ON" timeframes. in theory changing the hot water ON time from 04:30am to 06:30am should save 1.4kWh of gas or 20p per day, see first graph/picture.

The second picture shows when I forgot to turn off the hot water whilst we were away. So no hot water was used this day yet between 20:00 and 04:30 the hot water tank lost temperature and required 2.1kWh (31p) to heat is back up, then 0.7kWh (10p) per hour to keep it hot. Then 08:00-15:00 lost temperature and required 1.44kWh (21p) to heat it back up, and 0.7kWh per hour after that. Total usage cost that day = 85p, when I used no hot water.

I appreciate I'm talking pence, but with prices only going up, reducing non-required usage might help others and add up to pounds per week.
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