Leave solar batteries out of the system until we have the house up and running?

[saveasteading]

We are fitting  solar and intended to include a battery system sized to suit estimated use.

But our electrician/plumber suggests we leave the batteries until the house is up and running, then size accordingly.

 

I was surprised, as it will take a year until we have reliable figures, and that's a year of not getting the benefit.

Plus we will not be getting in the habit of optimising.

 

The vat reclaim entered my reasoning until I twigged that it is zero anyway.

 

Is the electrician wary of estimating wrongly? Or wise?

Or perhaps undersizing or oversizing is more than a cash issue.

 

He also agreed we should get a 3 phase heat pump, which the solar people were resisting. 

On the principle that as we have 3 phase we should use it.

 

Thoughts please,

[JohnMo]

13 minutes ago, saveasteading said:

agreed we should get a 3 phase heat pump

If your putting a battery to cover your whole winter loads, it going to be huge and not cheap. I would size it now for an average winter day. But your tariff makes a big difference to the size, Cosy gives you 3 charge periods, a typical electric car tariff only one, so you would need a much bigger battery.

 

Just choose a battery that can be expanded, add more later if you want as slave units.

[SimonD]

It's funny you should raise this difference between heat pump installer and electrician. The electrician I use as part of all my heat pump installations called me a while ago pretty p***ed off. He'd completed a new house wiring installation plus solar & batteries on 3 phase. The heat pump people came along and just installed a single phase heat pump cascade, causing a bit of a headache. At least yours are talking about it. What is the size of your heat pump? And I'm guessing it's been confirmed the model is available on 3 phase? Probably a silly question.

 

I've had a similar experience with solar design for my place where the designer didn't seem to understand modular and phased approach. It's a bit infuriating. With the right system design there should be no problem scaling up if you need to, just as @JohnMo suggests. 

Edited 1 hour ago by SimonD

[Russdl]

The battery would be VAT free during the build and maybe VAT free after. They became VAT free (outside of a new build) a couple of years ago and for sure that gift will be removed at some stage in the future.
 

Definitely get the battery when you’re building, they change the game entirely compared to just solar PV.
 

It’s costing us naff all to run this house (and hybrid car) the battery and off peak tariff is a large part of what makes that possible.