I get what you are saying about batteries and I accept that I am an early adopter and won't get back the money I've spent; to me, it is a hobby, an exploration of what is possible and may come in the future.

The PowerVault battery has a schedule and five settings:
- Force Charge
- Only Charge
- Normal (charge when producing excess power from PV, discharge when solar is insufficient)
- Only Discharge
- Force Discharge

On a daily basis, I can alter the schedule to force charging when the price per unit of electricity is low (normally below 6p per KWh wholesale) then only discharge when the cost of electricity per unit is high (normally above 10p per KWh wholesale). If it is a sunny or light cloudy day then I can set it to normal, whereby the battery will charge when excess electricity is produced (rather than export to the grid and earn next to nothing), but if I turn on the kettle, the washing machine is heating water, etc. the battery will discharge over and above what the PV array is generating, avoiding importing from the grid. Having the ability to set a schedule changes the dynamics of the return on investment, but I'm under no illusion that over 20 years I'll make a loss.

The downside at the moment is the PowerVault schedule and setting are all all manual. I can see from the web page, using browser dev tools, that they have an API but it is private, undocumented and requires an API key that is generated from authentication. I am hoping that they open up the API in the future. At that point Idratek and Cortex would come into its own; being able to turn things on and off depending on the cost of electricity would be fantastic. If the cost per unit is low or the battery has capacity then appliances come on, but when the cost is high or the battery is low/needs to charge then the load is reduced to essential baseline.

I see this as an experiment and fascinating. It would mean that we could really move to renewables which suffer from unpredictability, smooth the electricity demand across the day and have really smart, grid-connected homes. But at the same time, it is frustrating because I can't see this happening for the masses.