On-grid domestic battery storage

Solarchaser

I personally think with a consumption under 3Mwh a year, you are going to really struggle to justify solar plus batts to be honest.
The savings are not really there for you.
I'd think solar alone could maybe work, assuming a low cost install.

If your CH is pretty new you may have a hot water tank as part of it, and adding a solar diverter could save you some gas, but you know I just think your low consumption makes it harder to justify the outlay personally.

That is, if you are viewing it as an investment. 
If you view it more like a mini project, thats a whole different ballgame 

diveleader

I'm in the geeky passionate category! 
I was with Octopus (at the old house). Without energy storage I think I would struggle to get my (albeit small) energy usage out of the peak tariff window. 
The other half is interested in having a split AC / heatpump fitted to the bedroom (as it get warm in there and she's early 50's, so getting hot flushes!!)

Maybe I can pitch it to her on being able to use the AC for 'free'.

diveleader

The boiler is  a 10 yr old Worcester Bosch Combi, so all mains fed. I am also looking at the logistics of fitting a pressurised cylinder with a solar diverter. 

Less adventurous, but our kitchen sink hot takes an age to get hot. I could fit a £95 10ltr 2kW water heater under the sink to supply it. With a timer or a Alexa initiated switch it could make a cost effective dump for more leccy (and would save some spinning of the water meter!)

You can see, I'm applying man maths to full extent here.

Solarchaser

Hey I'm in no way trying to argue against man maths.
If you have read this thread, you will see im in the category of unlikely payback, I view it more of a pet project/geeky obsession/ testing theories. 
I am similar to you in terms of around 12 year old gas combined, no hot water tank. I really don't like the cold, warm, cold, hot cycle to get hot water from the combi, and will be fitting a hot water tank to replace the combi heating hot water.
But to make it purely about cost savings.... yeah I cant do it, as they don't really add up, especially if its a thermal store rather than vented cylinder.

JKenH

diveleader said:

I'm in the geeky passionate category! 
I was with Octopus (at the old house). Without energy storage I think I would struggle to get my (albeit small) energy usage out of the peak tariff window. 
The other half is interested in having a split AC / heatpump fitted to the bedroom (as it get warm in there and she's early 50's, so getting hot flushes!!)

Maybe I can pitch it to her on being able to use the AC for 'free'.

When I had my solar installed it came with a 3kwh battery which for various reasons didn’t work out so the installer removed it and refunded me. It did though make me want a good battery system but the maths never added up for me. (I can’t have a smart meter so don’t benefit from smart tariffs but have E7.) The problem for me is that there is never enough spare solar to charge a battery in the winter and my net consumption is only about 4-6kwh a day for the sunniest 6 months of the year. So with a perfect battery installation I would save about 1000kwh a year at most. 

What I do have though is a solar diverter (IBoost) and over the 22 months I have had my panels I have saved 2640kwh. As that displaces either E7 or oil it has saved me in the region of £100 per year. So the payback on that is much better than a battery.

As for solar panels if you are a bit geeky (I think we all are on here) then just get them. I am retired and get a lot of fun out of checking the output and comparing statistics.

I also have a couple of Aircon units (ASHPs) which I find very economical to run compared to oil (although with the domestic oil price recently halving the savings are not so great now and probably wouldn’t beat GCH which you have).

diveleader

Thanks for them comments so far.
One other question - I keep on seeing Eco-cute on my google searches. (most likely they are spending ++ with Google!) They seem to offer both std PV and battery backed. The web prices don't seem to bad. As anyone had any experience with them?

joefizz

The figures dont add up if you use current prices on some of the english tariffs but I should really bold the word current ;-)

It depends on a lot of things and Ive certainly found more ways to use a battery and save money elsewhere (ashp/immersion reducing oil usage although at current - that word again - prices it makes no sense).  Air con has been a godsend earlier this week when I needed to be in the home office for a couple of hours with 2 computers going etc etc. Never envisaged when I bought the ashp that Id use the air con function in this country ;-)

Ive moved back to using old electric lawn mower vs petrol and mains powered/air powered tools rather than battery units which need batteries replacing every few years (and corded versions are cheaper etc). Inflatable hot tub went up this week and infra red sauna was also used a few times this month. Will be making batches of beer next week with 'free electric' so just costing me grain, hops, yeast etc. Not exactly money saving if you are on one of the cheap english tariffs but over here in NI with no standing charge and 18-19p a unit its not bad.

Certainly got used to sticking the immersion on for 15 mins before a shower and got used to really hot water for it compared to the water heated by oil some time early this morning.

Unless you are really unlucky you are looking at at least a 10 year effective install but with a modular battery system later changes and swap out/repairs make the  monetary impact of repairs/upgrades down the line less of an issue.
If you have the money then you can balance out what you would earn in interest compared to the savings in not having to buy electric right here, right now.
It will also depend on your view about what happens to energy prices going forward.

diveleader

OK, some updates and your opinions on the two contenders please.
On a side note, I have ordered the install of 2 ASHP's (one for the bedroom (COOLING!) and one for lounge (heating, shoulder months). So I am seeking ways to increase the electricity consumption and reduce gas usage.
My quotes come down to 2 systems.
5.5kWp array, 6kW inverter and Powerwall 2
5.5KWp array. 5kW inverter and 3 x 2,4kW pylontechs

Happy with both installers, seem professional, answered questions well etc.
The Powerwall setup comes out £3.4k more expensive.
The Powerwall has twice the capacity, better thermal management and can go in the garage.
The Pylontech's are modular, so easier to expand, replace etc. but have to go in the house.

What would you do?

Solarchaser

I'd ask why the powerwall can go in the garage but the other one can't?
If you spent the 3.4k on 4 more pylontech you would have more capacity than with the powerwall. 

The one thing I find weird is doing a 6kw inverter with 5.5k of panels, generally its better to go with more panel power than inverter power as its more efficient,  as the times you will make 5.5kw will be few, so you want better efficiency at lower sun levels.

That said, I do belive the powerwall is a better system overall.
I went with pylons because they were much cheaper, and of course modular. So occasionally you can pick them up cheaper. 
I got 4 for £2k earlier this year.

joefizz

diveleader said:

The Powerwall has twice the capacity, better thermal management and can go in the garage.
The Pylontech's are modular, so easier to expand, replace etc. but have to go in the house.

What would you do?

Sorry, coming to this late. Same choice I had. Pylontechs and inverter can also go in the garage AFAIK as that was one of my choices but I chose to install in the spare room to use some of that residual heat to reducing the heating required in that room.

Leaving cost aside I went with the pylontechs purely because of the modularity and knowing that at some point they will fail or a section of them will fail and my thoughts are that they will be easy to replace. Both pylontech and powerwall are effectively large banks of smaller cells but for me it was easier to take one of the pylontechs offline, fix it and then replace, rather than have to fix the whole thing. With the powerwall (or LG etc)  its a nice neat all in one solution but it also a single point of failure, and whilst separate inverters and batteries are also single points in themselves, easy to get a replacement (or different inverter entirely but use the same batteries).

Check out the inverter oversupply capacity. In some this is as much as 20% so a 4k inverter might take 4.8k peak which might be all a 6k array ever puts out in your orientation. The numbers are just nominal, it will depend on your situation and siting etc.
You can always add extra panels on to the end of your strings (I did) after a year or two of usage so you know the max your system tops out at at the end of June.
I started with 4.8kw pylontech and then doubled it for a number of reasons, found I could use more in summer (hot tub, beer making etc) so could use the extra capacity, modularity and for the rest of the time, spreading the load across more batteries, hopefully extending life a little more.