Fast forward into 2024

April not quite over yet, but still looking good......

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Automation tasks underway

I have the following automation tasks underway, in various stages of completion: If there is a suitably inexpensive timeslot overnight, use it to top up the batteries to 100%. Using this, instead of solar, will allow more solar to be exported at 15p/kWh. Inexpensive slots during sunlight hours are not as useful because I can't export at the same time as using electricity from the grid. If there is not a suitably inexpensive timeslot overnight, top up the batteries from the grid during the period coming up to peak time (which is usually fairly reasonably priced). Make sure any battery charging from the grid is definitely off before the 4pm-7pm peak rate starts. When the electricity price goes negative, boost the hot water temperature using the heat pump and immersion heater. This is a way of benefitting from being PAID to use electricity and storing a little of it in the form of hot water. Change the colour of a lamp in the kitchen to reflect the current electricity...
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Calculating the cost of using your batteries

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UPDATE: I have made a cost calculator spreadsheet (see link at bottom of page). I have posted this graph elsewhere. It makes it easy to estimate a notional "cost per cycle" for a LiFePO 4 battery. It can be instructive to calculate what the "cost per cycle" means when viewed as a "per kWh" value. When you calculate your "cost per cycle per kWh" don't forget to include factors such as: Charge/discharge efficiency (say 87% to 90%) Depth of discharge (obviously reduces the effective capacity) Average capacity degradation over the life of the battery (say degradation to 80%-90% at "half spent" point) It is easy to see that the cost per kWh of passing energy through your batteries can easily be in the region of 10p-15p per kWh of "delayed consumption". Knowing that figure helps to put a priority on storing the various "types" of kWh that you choose to store. It may change your perspective on exporting ...
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The dreaded DNO and G99

Before long, you are probably going to hear the term "DNO Application" or "G99 Application". This refers to an application to the Distribution Network Operator (the people who manage the cables, poles, transformers, etc., that bring electrical power to your home). For any solar instalation greater than a certain size (I believe 3.68kWp at the time of writing) an application to the Distribution Network Operator must be made. This takes time (about 3 months in my case) and often money (I was charged an extra £450.00). Because of this, there is a big incentive to a salesman who wants to make a sale and move on to recommend an installation smaller than this critical size. Many users, with relatively low electricity usage, will be fine with a system of less than this size. However, it is worth being aware that this issue exists. I use the term "Dreaded G99" because some installers will avoid it because it can be a lengthy process over which they have little, ...
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