System, 8.5KW solar panels & 15.6KW battery storage. Had the batteries installed 5 weeks ago and the Solar panels fitted recently, everything working great to date but am trying to balance or maximise the savings utilising our dual tariff which starts at 00:30 to 07:30. Can be weather dependant were the panels only generate enough solar to cover our base usage during the day just wondered if anybody else has had alonger period to annalyse the data and make an informed decision, set the batteries to charge during the night tariff or leave the system in Eco mode.
Andy
You can use Home Assistant to automate the following days charge based on the weather forecast. Probably getting into the wrong time of year for that to be most effective though.
Do you have a BEV?
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#3Tim
AndrewRoberts My take is that it depends on the prices for your off-peak, standard and SEG tariff. I'm guessing your tariff is Economy 7, so the difference between standard and off-peak won't be that much (maybe half?). The solar forecasting that some have developed is reported to be working well and that may be your best route to your answer. However, only you know how much energy you use on a typical day and how much of that can be supplied by PV/battery. It also depends on whether getting it exactly right is the goal, or if just saving money is good enough. We are able to charge the house batteries each day and the EV during the day from PV. We know that at some point in the late autumn/early winter that will change. We will have to charge overnight (house and EV) to avoid the standard rate tariff. Fortunately, the difference between our off-peak and SEG tariff is about 0.4p/kWh so if we overcharge the batteries and have a really good sunny day, we will have spent pennies more than absolutely necessary. That's good enough for us. If we don't charge the batteries enough and have a very poor PV day, we would have to import at standard tariff, which is about 35p/kWh more. It's a no-brainer for us.
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#4AndrewRoberts
We have a base usage of about 0.7KW and our peak usage starts in the evening when using the oven etc.. currently don't have an EV but looking. Avergae daily cost before the batteries were installed was approximately £15.00 per day, once up and running and charging on the night tariff (£0.22) that daily cost went down to £7.50 so a good saving, now the solar panels have been added to the system and on a reasonably sunny day the daily cost went down to £1.50 (day tariff £0.50) so in all a very good saving. I asked the question originally because I started to set the battery charging period based on the night tariff and the daily cost has now gone back up to around £6.00. I think I will leave in Eco mode for now and change to charging on night tariff when sun hours become shorter and weather worse probably end of October, thank you both for your thoughts.
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#5Tim
AndrewRoberts In the spring we had a few days where the battery was only charged to about 60% by the end of the day our to poor weather. By the end of the following day, the SoC started at about 20% and rose to a paltry 40%. By that evening we were importing. My take, given these figures, would be that I would want the battery to charge to 60% by the end of the off-peak window to get me through to the next window. Better for you to overcharge slightly at £0.22/kWh than to risk £0.50/kWh? Our break-point on risk vs reward will be 80% given the difference we have (£0.045/kWh vs £0.395/kWh).
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#6anthonypar
Just set the inverter to eco mode and gradually increase the battery 'charge up to' percentage during your off peak period to cover your usage during the day. As less solar becomes available during the winter months the more you will have to charge up the battery via the 'charge up to' setting.
