Mindful that this thread is a dull as dishwater to most members, but it’s useful for me to both log how our energy costs are changing and to receive comments and ideas from other members. In time we may install a solar roof (waiting for Tesla to launch in the UK). So the latest update…
We’ve kept the heating set to 22 degrees for 24 hours per day since before Christmas, and as the weather has warmed up the daily cost has reduced steadily. I was hoping that we’d be able to switch the heating off from the end of March, and we’d see a dramatic reduction in cost.
We’ve been away for the last 10 days, so before leaving I turned the heating thermostats down to 11 degrees. As the internal temperature was unlikely to fall below that, the heating was as good as switched off. Having forgotten to switch it off, I left the hot water on 24 hours per day!
When we arrived home this evening it was 12 degrees outside according to my phone but 15.4 degrees according to ventilation system. Inside the warmest part of the house was 17.5 degrees and the coldest was 16.8 degrees. Based on that I think it’s unlikely that the heating would have kicked in at all during the time we were away.
Taking the “used this week” figure on the smart meter, and pro-rating it to allow for the remaining few hours of the week, it looks like we’ve used £9.35 (81 kWh) of gas per day whilst we were away. As there was no heating on, then I can only assume that is the cost of heating the water 24/7.
That may be artificially high because we have a pump which circulates the water around the house so you don’t have to wait more than a brief moment for the hot taps to run hot, and yes I also forgot to turn that off, so we’ll have been cooling and reheating more water than we needed to.
Pro-rating the electricity consumption in the same way shows that we’ve used £2.85 (46 kWh) of electricity per day. During that time there was minimal lighting - randomised timers on ambient lighting and PiR triggers outside - plus the air circulation system set on it’s lowest fan speed.
In March we used around £20 of gas and around £7.30 of electricity per day. When the house is unoccupied we use 40% of the electricity and 45% of the gas compared when the house is occupied. The weather has been a little milder in April so it’s probably around 50% in practice.
The biggest surprise is that it would appear that the cost of heating the water is a big proportion of the gas consumption (and therefore cost), around 50% in March/April. I’ll do some experimentation to measure the difference of heating water on a timer, and turning off the hot water circulation pump.
