Never enough battery storage

First of all there is never a right size of battery. Some days it will be too big. Some days too small. Seasons change the amount and when you use power as well. You may outgrow a small system. You may under utilise a large system if your circumstances change. As I said in my blog on the economics of solar and battery systems, solar plus a good SEG can't be beaten. If you can't get a SEG or the SEG rates go down a lot then a battery is the only way you are going to be able to use all power you've generated.  The lower the SEG the bigger the battery you need.

One day I might do the maths on how you determine the best battery size but right now the cloakroom is mid revamp and I've been given a deadline with the emphasis on dead.

There are significant complications with determining the ‘right’ size of battery. As mentioned, circumstances change as does family size and needs over the years.

One thing that needs to be added into the mix is ‘off-peak’ or low cost charging of the battery .. often in the depths of winter, this becomes very useful. Indeed, if you follow the market with a tou tariff such as Agile for example, you can charge the battery for next to nothing, or in some cases, with a cost positive contribution. Then, even if not needing the battery power for the home or EV, you can export any excess power at times of significant use (peak hours?) helping out the local supply as well as earning from your export.

This used to be seen as gaming the system but these days, I’m not so sure. It’s not something anyone on FIT can do as they use a NET generation meter which treats charging from the grid negatively on count up but I do know that it happens quite a bit already. Especially by those with automated monitoring and activation systems.

* good luck with the cloakroom revamp 

The elderly toilet had become incontinent (it happens) and damaged the laminate flooring and as I had revamped the kitchen flooring (and had bought matching flooring for the cloakroom) I had run out of excuses not to replace the flooring, the toilet, the basin and the boxing in of pipes which needed the wiring for the car charging moving etc etc ... It's next on my list to do.

One thing to remember about Agile is that its not the peaks (boo) and troughs (hooray) that you need to talk about because at the extremes they are rare but the average value for the equipment you use, when you use it. ToU charging the car (am or pm) ~12p and Immersion Heater ~15p. Non ToU domestic (including peak usage)  ~19p. Now the immersion heater doesn't look like a good price but when you couple a 6.2p gas price with a 55% efficiency then you get a cost of ~11p for gas which makes 15p not so bad in comparison. And you are not burning gas as below.

Peter

In general, there are always ‘lower’ cost periods on a tariff such as agile 

These also correspond to greener slots from grid emissions 

Therefore with any spare battery capacity, you can make use of lower cost energy and use it to power the home as needed through the other periods of the day. 

* I once had to do a similar job in our kitchen (different house, many years ago) but I was not so familiar with plumbing techniques and therefore, initially, I added to our water leakage rather than fixing it. Give me simple electric supplies any day!

And the afternoon troughs will now only deepen and widen as we go into summer. There a loads of commercial solar projects (>0.5GW) coming on stream this year and, unlike offshore wind, they are very fast to get operational. On top of there there are three gigawatt size offshore windfarm schemes coming on line this year. Dogger A, B and Sophia off of the Humber estuary with a total of nearly 4GW.

I do plumbing as well (the toilet went in with zero leaks) but at least that only gets you wet if you get it wrong. Electricity bites back!