On Thursday I kicked the underfloor heating into action, resulting in our electricity usage being the highest ever in terms of cost. However, it was nowhere near the highest in terms of kWh used.
Thursday, for example, when the concrete pad had to be heated from 14 or 15 degrees to over 23 degrees, resulted in 75kWh and £27.08 in cost, equating to £0.36 per kWh. The highest ever power usage was 128 kWh on the 31st December 2020, when I had two sons living in caravans in the drive, but that was only £20.46, equating to £0.159 per kWh, and was in the middle of a period of having the heating on permanently. It has more than doubled in price.
Here's a chart of the daily usage since moving into the house (click to enlarge). The yellow is solar generation and the blue is usage - both in cost. On the extreme right is usage since Thursday, which goes all the way to the bottom of the chart area.
The following chart is annualised usage in kWh by day and, as you can see, it's still plummeting due to not having had the underfloor heating on (and no 20-something kids living in caravans).
Doubtless this will shortly start to increase with the underfloor on. There's no real need to cut back, as I'm currently £1,900 in credit with our electricity bill.
That said, Friday's usage extrapolated over a month, not counting the feed-in, equates to over £800 a month for winter, but a lot of the usage was expended in the start-up operation. Today, seeing as we only really need to heat the spare bedroom in preparation for some No.2 Son returning from Uni over Christmas, I'm going to revert to the 12.3 kW log burner for the rest of the house, which I estimate is costing us £130 a month in winter.
I totted up the cost in electricity since moving in 9 (nearly 10) years ago and it came to just over £17k. Contrast that with the £13.3k recouped from the feed-in. So, it has cost us £3.7k to run the house over 9.5 years - £389 per annum, or £32 a month for heating, cooking and lighting.
Talking of heating, I have a friend who owns a small car lot and garage. He's recently opened a much larger indoor garage unit where he can perform MoTs and more complex work. I was intrigued by his blown air heating system which, at first glance, burns heating oil. On closer inspection, and after chatting to him about the system, it transpires the boiler burns old engine oil, of which he has a plentiful supply. He even collects it from other local garages who have to pay a fortune to have it removed.
It burns well, leaving a solid clinker residue which he has to clean out every couple of days. It costs him nothing to run and actually saves paying to have the oil taken away, but it isn't exactly the greenest of fuels. It burns some 20 litres of oil a day. The clinker is actually used as hardcore and I'm thinking of asking him for a load to fill potholes in our drive. As it happens, he fortuitously had a pile of Type 1 spade that he let me have for free.
On Friday he did an oil change on my Ford Galaxy - I was tempted to ask for a heavy discount on the oil change as I was subsidising his heating cost with my old oil.....
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