Solar diverter - flawed return on investment calculations

JKenH

Screwdriva said:

JKenH said:

I am not suggesting batteries don’t work with Flux - they do, you get the best of both worlds. I think the argument that @Screwdriva was making is that if you don’t already have batteries, Flux is a good alternative at no capital cost and the question anyone now considering batteries needs to ask is once I have Flux, how much more will batteries benefit me?

I very much understand the satisfaction of being more self sufficient and batteries storing energy are more satisfying than just saving money. You obviously appreciate Flux but others having spent money on a battery system (and seeing the higher overnight rates on Flux) are happy to just minimise overall draw from the grid (their import bill) rather than look at the net bill after taking export into account. 

To further highlight JKenH's above point, here are two scenarios of Flux (one with and one without a 10 kWh battery), using our actual consumption pattern, generation and export. (Highly recommend Gary's new Solar Calculator)



vs. Battery (set to charge fully from 2-5am and discharge during 4-7pm)



Without drastically increasing our consumption, it's unlikely we will recover the cost of the battery within the warranty period. 

That’s interesting, thanks. I was, though slightly puzzled by the figures as though the extra import cost is £1.95 and extra export value is £3.01 (£1.06 difference) profit increased by £1.66. Am I missing something? 

Screwdriva

JKenH said: Am I missing something? 

I wanted to be as fair to battery owners as possible and set the tool to force discharge the battery at the peak export tariff offered between 4-7pm.

Even with this, evening only consumption and only a 3% AC/DC conversion loss, £1.66 of profit is the best we would achieve over a PV only system. 

JKenH

That would earn the battery owner £600 per year.

Petriix

JKenH said:

That would earn the battery owner £600 per year.

So ~ 10 year ROI in ideal circumstances, and only if electricity prices stay this high. Seems reasonable. However, £6k into an index linked ISA or just overpaid on a mortgage and you do a lot better...

Screwdriva

Petriix said:

JKenH said:

That would earn the battery owner £600 per year.

So ~ 10 year ROI in ideal circumstances, and only if electricity prices stay this high. Seems reasonable. However, £6k into an index linked ISA or just overpaid on a mortgage and you do a lot better...

Three additional factors:

1) Its hard to find a quality 10 kWh battery installed for ~£6K these days.
2) More worrying for industry old timers like me, is what happens when the 10 year warranty comes to an end. No one knows how long modern home storage will actually last. 
3) Is a 10 year ROI worth purchasing a product that should really be put into an EV?

orbit500

Petriix said:

JKenH said:

That would earn the battery owner £600 per year.

So ~ 10 year ROI in ideal circumstances, and only if electricity prices stay this high. Seems reasonable. However, £6k into an index linked ISA or just overpaid on a mortgage and you do a lot better...

Excellent point and rarely mentioned.
I ran multiple simulations before buying the batteries. Originally I was on Go Faster and mining Ethereum at 35MWh(!) annually, with 28kWh under £7k. Now on 4.5p overnight my total bill is under £40 a month vs £300+ without. I have an Eddi to mop up excess as I’m on deemed export.
I wouldn’t do it again now as those same batteries are £12k and electric is too volatile to make a 7 year call.

silverwhistle

JKenH said:

No, it was claimed RE will make prices cheaper, and look where we are now.

With even more expensive gas generation if we didn't have RE. Remember the cheaper CFD wind has been paying money _back_ to the government.

Waywardmike said:

Here's my experience with an iBoost...

If it broke would I buy another?  No. 

Good point. Tempting fate but mine has lasted 10 years. Now I have cheap overnight charging with Octopus Intelligent and a large battery in my EV I might look for a solution that involves the latter, when it breaks. Given the annoying nature of clouds that seem to dwell in front of the sun when you are otherwise generating 2-3kW and using the EV granny charger I'm not sure what the cheapest solution is.

JKenH

silverwhistle said:

JKenH said:

No, it was claimed RE will make prices cheaper, and look where we are now.

With even more expensive gas generation if we didn't have RE. Remember the cheaper CFD wind has been paying money _back_ to the government.

. 

But that isn’t bringing down the price to the consumer - as explained on the G&E Issues in the News thread

zeupater said:

Hi

The issue at the moment is that due to the way the electricity market works, however cheap the strike price is, the consumer doesn't benefit .... we either pay a subsidy through general taxation, or the 'negative subsidy' is wasted by the government through fund reallocation ....

It's high time that the electricity market is uncoupled from the inherent volatility of fossil fuel pricing .... it'd be easy to do, just base wholesale pricing on supply bid average pricing for a given period and the cfd system works as designed thus reducing consumer prices ... it's really down to Ofgem to pull up their socks and start doing the job they're paid to do, it's not that there aren't enough of them to allow their cumulative IQ to equal that of some nobody on the internet,  so why can't they come up with a such a fundamentally simple solution ... ?? ... Vested Interests?

HTH-Z

Martyn1981

silverwhistle said:

JKenH said:

No, it was claimed RE will make prices cheaper, and look where we are now.

With even more expensive gas generation if we didn't have RE. Remember the cheaper CFD wind has been paying money _back_ to the government.

Waywardmike said:

Here's my experience with an iBoost...

If it broke would I buy another?  No. 

Good point. Tempting fate but mine has lasted 10 years. Now I have cheap overnight charging with Octopus Intelligent and a large battery in my EV I might look for a solution that involves the latter, when it breaks. Given the annoying nature of clouds that seem to dwell in front of the sun when you are otherwise generating 2-3kW and using the EV granny charger I'm not sure what the cheapest solution is.

Yep, across Europe as a whole, if we had less RE, then the demand for gas would be even higher, pushing the market price even higher, pushing the leccy price even higher.

JKenH

My reference to RE was in the context of making decisions about investment in batteries based on predicting the direction of travel of retail electricity prices; how the expectation 5 years ago had been that with the roll out of more renewable generation we would not see the continued historic rise in prices but things didn’t turn out that way. It was not my intention to start a debate on the merits of renewables but simply to illustrate that while we can speculate about the future travel of prices based on what we know at the time, things don’t always work out as expected.