Solar panels + battery from Ovo: good or bad?

I will try to put some calculations together for you. My comment comes from my own experience of an installed system which cost around £8k and which paid back in under 8 years coupled with the current quotes I see for a G98 compliant system (3.6kw) costing between £5.5 and £6k.

My own tech uses a LuxPower inverter and Pylontech battery modules.

Whilst I appreciate that this isn’t specific enough, it is a reasonable assumption plus looking at increasing energy costs and therefore increased potential savings.

There are also individual factors to consider such as usage, location etc.

Thanks @BPLightlog  I’d appreciate that.

Interestingly, the quotes I had showed no difference in payback time between solar-only and solar + battery systems. By my analysis, that means the extra cost of the battery isn’t sufficiently offset by the saving in electricity consumption to be worth having…

Whilst I understand that calculation, battery storage in my view is vital to make the best use of solar PV (it never generates exactly when and what is required), plus battery storage allows increased flexibility in any grid usage meaning that time of use (ToU) tariffs can be targeted to give lower cost for any excess grid usage required. 

*This is a rough calculation and will not be valid in every case
If I take an example of an Ofgem ‘typical’ medium sized household consumption of 2900 kWh

at a ‘current’ rate of 20.6p per kWh cost would be approx £600 (excluding standing charges)

For a 3.6kw (G98) solar PV system I would expect around 3500 kWh of generation (shading, latitude etc obviously affects this)

I would expect solar PV + battery to cover at least 90% of usage. The remaining 10% usage from grid, with the flexibility of battery storage, can provide a further reduction in cost utilising a ToU tariff. This can result in a total annual cost of approx £12.50 (290 kWh @ 4.3p per kWh) plus standing charges. 
With battery storage, both excess generation and ‘phased’ charge/discharge cycles can be utilised. 
My own stats show export of around 1500kwh which can be redeemed at anything up to 20p per kWh. (I use 15p as that is my export tariff).

Additionally, with a ToU tariff, you can combine charge/discharge cycles which I approximate to 450 kWh. This technique allows charging ‘off peak’ at a variable rate (often negative cost) and exporting at standard rate (say 15p) which adds to the cost of savings. 
In the first year, this amounts to £910 in savings 

587 (reduction in usage) + 225 (general excess export) + 100 (charge/discharge cycles)

I have taken subsequent years at a 3% uplift but a 6 year total saving would then be £5900

As I mentioned at the top of this, there will be individual circumstances which affect this calculation but the calculations are from my own experience 

> I appreciate that this is a ‘best case’ scenario and also that ToU tariffs are not available from all providers. However, if someone is investing in solar PV and battery storage, it would seem sensible to make use of all potential advantages 

Hi @BPLightlog , thanks for taking the time and trouble to produce these detailed calcs. All very illuminating, from a variety of points of view.

Firstly, your calcs rely on something like Octopus Agile/Tracker to work, and assume significant time-shifting of consumption to extract the most economical performance - correct? I’m not sure I’m up for that level of engagement!

Secondly, your final 6-year figure of £5900 is interesting. The cheapest Solar + Battery quote I’ve had so far has been north of £10,500 - admittedly for a bigger (4.8kW) system than you are hypothesising. Are you really suggesting dropping the system size down to 3.6kW would halve the cost?

I have a new installer coming today to take a look at my place. It’ll be interesting to see how his figures come out.

I would be interested in any updates after your visitors @MikeyB .

I do use an Agile tariff as it provides the best value for anyone who can shift their major usage in a controlled way. It’s also much better for reducing emissions. I have recommended that OVO offer something similar but there is nothing currently available from them. 
I used a G98 (3.6kWh) system firstly as that is what my own system is based on and not everyone can get approval for a higher level. (G98 is fit and advise, G99 + is get approval before fitting and connection). If you can get approval for a higher level then it may well be worth it for the additional generation and potential export income. 
My own system is fairly automated to automatically charge at certain levels but I do occasionally initiate a manual charge/discharge cycle. 
Although I’m quite technically aware, I am approaching the ‘ancient’ level and so am not completely up to date on everything and of course I have not purchased a full system myself for over 10 years. The prices I quoted came from online research. 
I can confirm however that my own system was well worth the investment and I would recommend solar PV to anyone who can access it. 

I will indeed report back. The installer has gone away with all necessary info and a promise to be in touch shortly. He too was talking, unprompted by me,  of ‘aiming for’ 6 years payback time.

Last year my electricity bill, excluding standing charges, was about £820.

So, here’s my back-of-an-envelope calculation:

To achieve 6-years payback, assuming the system makes me 100% of my electricity, and I export say 2,000 kwH at 15p (ie £300 ‘income’), and assuming 3% per year increase in prices, the system needs to cost less than ((820+300)x6)x1.19 = £8025

Let’s see what unfolds...

Just another thought to add into the options .. there is the OVO Solar offer of course - there is a higher SEG return and what looks like a reasonable financial plan. 

Ah, I tried. They told me they won’t install panels on flat-roofed properties like mine unless I agree to a “full “ (ie expensive, messy, invasive, destructive) structural survey.  This was despite me making the design drawings and structural calculations available to them. Totally frustrating!

I also hit a brick wall with Octopus, who replied that they weren’t installing panels on flat-roofed properties “yet”, whatever that means.

The problem really is that these companies are using cheapo installers who just want to do the quick, easy, low-risk jobs - the low-hanging-fruit approach - and anything that might slow them down or cause them to have to think is just not worth the trouble to them.

I hadn’t picked up on that. The panels will need angled ‘platforms’ to mount on of course but it sounds like you’ve already considered that. 
I do know some who have used that option along with some additional support for wall mounted panels to extend their available area. Well your recent visitor sounded like they were up for it so hope you manage to get a suitable package.