Ever decreasing circles - which solar setup to go for

Slinky

Like so many others I'm trying to make a decision on what solar route to go down. Our current annual consumption for electric is about 3100, in a 2 adult home, one working from home 3 days a week, other retired. No electric vehicle, no plans to get one at this point but may be a long way down the track.

Struggling to chose between 2 options with same supplier who is price matching another.

10 Trina 410W Panels

Pylon Batteries

Hybrid Inverter

With 4.8KW battery £10K,

with 9.6KW battery £12.1K. 

Additional Eddi device £500.

All installation costs, pigeon proofing included.

Payback periods as shown, we were all set to go with the 4.8 battery but reading about the various Octopus tarriffs it seems the straight line figures used in these estimates aren't representative of the latest ways of pricing for export, so we're now uncertain of what to do. We've been talking about this for so long, I just want to make a decision and get on with it.

We have gas CH with a new boiler and a new 210 litre hot water tank, not sure whether the eddi would be a good choice or not.

Can anybody help clear our minds and help make a decision please?

Reed_Richards

Slinky said:

Like so many others I'm trying to make a decision on what solar route to go down. ..... but reading about the various Octopus tarriffs it seems the straight line figures used in these estimates aren't representative of the latest ways of pricing for export, so we're now uncertain of what to do. 

It all depends on how you see the future for Octopus.  Perhaps they are ahead of the game in the higher tariffs they offer for export and sooner or later other companies will follow suit?  Perhaps they will continue to be an outlier but remain profitable enough to maintain their position?  Or perhaps they won't survive and the good export rates you can get from them now won't survive long into the future?  I have no idea which it will be but if you base a decision that relies on current Octopus export rates remaining, then as things stand you are putting all your eggs in one basket.  

Alnat1

I've held off with a solar diverter for the hot water tank for now as I can get more per kWh exporting the electricity than the gas costs.

If/when it gets more expensive to use gas, I can think about fitting one then. Or maybe by then it'll be time to think ASHP?

cm4ever

From my personal perspective, simple answer for you without mucking about - if you can afford it go for the bigger 9.6kWh battery.

The longer reason, in my case:-

My install as detailed in the signature was based on wanting solar & storage as a way of being more self reliant - yeah it's grid tied but that's not the point. 
 
In our case, I was consciously guided to the larger battery storage by following the experience of someone I work with who'd previously had their solar & battery storage installed 6months earlier and is already talking about wanting to get another 2x batteries, as they only got 2x batteries at the time of their install. In both our cases, the battery storage is made up of multiple 2.4kWh battery units i.e 2=4.8kWh, 4=9.6kWh. But uHome units have a theoretical max 90% depth of discharge therefore 9.6kWh is really 8.8kWh.

Finally, I was also comparing quotes with a large 10kWh power wall unit (which was really 10kWh usable, as it is technically made with 12kWh) but the only suitable place for the storage install (in my mind) is inside the loft, the power wall was big(!) hence multiple battery storage units had to be used.

Just remember, once you've bought the system and spent the cash, upgrading later could be cheaper depending on future costs, but you'd also have to factor in inflation, as well as any price drops and potential complications on who would be able to upgrade the storage (with reference to changes to a probably 10yr+ warranteed system installed by whoever you end up choosing....)

Just some food for thought, I'm not even going down what seems to be the forum standard RoI debates......

Slinky

I am now swaying back towards the larger system. Has anybody regretted buying a bigger battery? Our builder regrets only having a 2.4 battery and is contemplating putting another in.

We won £550 on premium bonds last month, so that's a quarter of it paid for. And if we don't have the eddi that's it half paid for.

Hmmm.

powerful_Rogue

Slinky said:

I am now swaying back towards the larger system. Has anybody regretted buying a bigger battery? Our builder regrets only having a 2.4 battery and is contemplating putting another in.

We won £550 on premium bonds last month, so that's a quarter of it paid for. And if we don't have the eddi that's it half paid for.

Hmmm.

I was quoted with a 6.hkWh battery and added a second to my quote for another £2400. It's just enough to cover the deepest darkest day in winter. Could be tempted to add a 3rd at some point in the future.

Alnat1

A year in and we are thinking of adding another 4.8kWh battery but we decided to start small.

We chose Pylontech as it's easy to buy and add more units yourself. To be honest if I was really thinking about ROI  we wouldn't bother, it's more of a nice to have. Yes, we'll have to pay VAT on it but we did on install anyway, as the VAT free scheme hadn't started then.

Edit - maybe ERNIE will buy us one too 

thriftytracey

I believe you are charged 20% VAT on an additional battery if you have one installed after your initial solar panel installation.

Screwdriva

Sorry to throw a spanner in the works, but given your lower than average consumption, have you considered skipping the battery altogether?

As you don't plan on getting an EV or a heat pump anytime soon, you will sell 100% of your excess energy to Octopus at .15p per kWh minimum. You would purchase your incoming electricity via their Tracker or Agile tariffs which average ~.25p per kWh. 

This calculator will show that the ROI is best for low users like yourself when you go pure solar PV and export to the grid. No diverter. No battery. (Battery advocates really only have "good feelings" left to praise when the numbers are estimated)

If things change in the future, you can always add a panel and a battery (no VAT) when the time comes. You can be assured the battery tech will have only improved and will likely be priced better. 

Finally, you should be paying < £6K for a 10 Panel 410W SHARP panel system paired to a SolarEdge hybrid inverter + optimizers. All with a 20+ year warranty. Less for the budget brands quoted to you. That's atleast £4K saved upfront.