Economics of charging at 7p and exporting at 15p

[Stinsy]

A few months ago I was playing some games to import/export in the hope of profit. Below are the results. I'm finding it difficult to understand what (if any) profit was made from my endevours. And I can imagine a whole load of problems:

• I can't know how efficient my battery charging process is in the real world.

• I can't know how efficient my battery discharging process is in the real world.

• Some of the income is from spilled solar that is incidental to my charge/discharge shenanigans.

• I cannot know how much wear and tear this additional charging/discharging is putting on my batteries.

• It involves contravening my principles regarding "dead-man's handle"*

I stopped the experiment because life was busy enough at the time, and there where a whole bunch of upcoming situations that'd require changing inverter settings one day then changing them back again the next, which is a faff that I try to avoid.

What do you lot think about the above? Do you charge/discharge for profit? Do you think it is worthwhile?






* I really don't like making changes to my inverter settings that would be detrimental if left as such. Obviously I do this for saving sessions and such, but I don't lie it and try to avoid doing it. (I don't see why the software controlling inverters cannot have the functionality to program setting changes to happen in future but hey ho...).

[Joeboy]

Been running the export for a couple of months. We export most of the generation & a chunk of the stack through the day then recharge late night when the grid is quiet. At the moment we export at 30% discharge rate 05.30 to 23.30 and it all gets done. I slide the export % about in the early evening if need be due to excessive solar gains. Cycles on the battery aren't something I worry about. When they're too low capacity to keep i"ll replace.

Certainly in the first 2 months we exceeded predicted deemed export figure for the year. I wish V2G had been made simple. A nodal leap forward, but it didn't happen.

We are running three SH's and HWT in our absence and I say to No1 son to use our house incl showers. He can charge his EV there too. Yesterday we bought 59kWh to do all this and charge stack. We exported 30kWh which paid for all that. We did it all through the night and exported when demand was higher. I like it.

[Moxi]

Hi Stinsy,

I'm late to this sort of thing - using batteries charged from the grid - and have just signed up for a smart meter, but I already know that for my personal needs I will only export excess solar generation in the summer and even then only if I cannot find a use for it myself. As time goes on I plan to deploy as much solar PV as I can to try and get the winter import down to a sensible minimum, the short fall between home generation and needs will be made up using whatever best ToU tariff I can get and use the home battery to shift this cheap power to when I need it.

I like reading about the stuff others do with export but its too sophisticated for me.

Moxi

[resybaby]

Thanks for the live examples of your calcs Stinsy, this is a topic that i need to get my head around, as during the summer we generate far far in excess of what we need, and, theoretically i can see some decent gains financially as a consequence.

But like yourself, if its going to need lots of monitoring and faffing about then id be less inclinded. I have spent a fair few quid on my batteries (cheaper of course via Colin, but i didnt think id have the time to learn/do all that), so i do consider the cycling of those batteries an integral part of any calculations. No use making a £ if you spend 99p to do it i guess being my viewpoint.

Doesnt help having a restriction on invertor size, although pleased to add i had an updated letter from the DNO last week after chatting to them, upping my export limit to 3.99 (based on my initial FIT system invertor size).

So will also be interested in others views/thoughts and will watch with interest.

[Joeboy]

I think we are on 6,000 80% warranty Lifepo4's. About 2 grand for 30kWhs. Export 70% of that to allow for 10% losses and 20% remaining in stack. At 8p per kWh profit that's.

30/100x70×0.08/100= £'s x365x16 =£9,808 less 2k build cost. Rough as hell and massively open to interpretation as well as a 16 year slide from 100%soh to 80%soh.

I have had 2 pints though but that's £7,808 across a battery set lifespan.

[Moxi]

All this chat made me go around to the MiL's just now and check her system and sure enough shes exporting solar power as the house battery is now full so I have applied for her to go on the outgoing fixed tariff so that anything she cannot use earns her some cash. It seems to suit what I need as I can spend my time and efforts using as much as I can and if any solar power escapes to the grid I can relax knowing its made me a little bit in return - the main game for me being reduce the need to buy premium priced power with the minimum of kit.

Moxi

[Stan]

Gary made an episode relevant to this subject. California’s solar policy over the years has been so successful that the duck curve falls below zero at the middle of the day. So the energy companies don’t want your export then. He can see the same thing happening in the UK before long, making export less profitable or a loss.

[resybaby]

Gary made an episode relevant to this subject. California’s solar policy over the years has been so successful that the duck curve falls below zero at the middle of the day. So the energy companies don’t want your export then. He can see the same thing happening in the UK before long, making export less profitable or a loss.

Can see the same risk over time myself Stan, things change fast around RE and the net zero push is no different. Equipment and tech has come on in leaps and bounds in a rather short timescale. Noble aim of course, no doubt, but pushed and pulled by those in control at their momentary whim, so best imv not to rely on todays situation to far into the future.

I recall the government trying to renegotiate the FIT contracts and getting the bums rush from the courts (quite rightly), so they realised the costs involved then. Is that why the SEG doesnt have any minimum payment applied? all depends on usage and market forces and at the whim of payer.

Short term however, until saturation in the markets, it would appear lucrative on the face of things.

[Stinsy]

I think we are on 6,000 80% warranty Lifepo4's. About 2 grand for 30kWhs. Export 70% of that to allow for 10% losses and 20% remaining in stack. At 8p per kWh profit that's.

30/100x70×0.08/100= £'s x365x16 =£9,808 less 2k build cost. Rough as hell and massively open to interpretation as well as a 16 year slide from 100%soh to 80%soh.

I have had 2 pints though but that's £7,808 across a battery set lifespan.

Thanks for the calcs.

Here is my back of fag packet effort:



I have to admit, it isn't particularly compelling!

What is the going rate for 15x LF280K cells these days? @colin?

[Fintray]

My main reason for the batteries was to import at cheap rate to prevent import at peak rate and for them to have enough capacity to power the whole house for at least a day.
During the summer and shoulder months I can export quite a bit but overall the target is to be cost neutral for electricity over the year.