I have my Givenergy batteries set to charge in the cheap 4 hour Go period whatever percentage depending on the next day generation. The key here is to keep the charge period for the whole cheap time zone (00:30 to 04:30). So if the batteries are full early they won't discharge to car, the car will be charging directly from the Grid in this same cheap period. By holding the batteries to the full cheap period it stops them discharging over the same alloted time.
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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
I use Home Assistant on a Raspberrypi to disable battery discharge during car charging. You can also achieve the same thing by stopping the batteries from discharging between 2330 and 0530.
WannabeOwner
Well-Known Member
Its more expensive too ... thus may not be an option for some folk.
My challenge in Summer is to have the cars below 50% - 'coz that's below the DRAG minimum on the dashboard.
My cars' charging flexes according to a combination of when I'm going to use them, and how sunny it is.
If I come home and the car is at 40% and I'm not going anywhere tomorrow / its sunny I definitely don't want the car to charge on Off Peak. (If I come home below 30% I will want to charge to at least 30% "soon", and if I come home below 20% I will charge to 20% "immediately" (i.e. using Peak rate if needs be)
If the car has 40% that's good for, say, 120 miles - that's a long unexpected trip for me
And the other car probably has more charge than that, so if I had to go somewhere unexpectedly I could take that (we prioritise charging the long-distance-preference-EV first / higher anyway, with the local/shopping EV typically maintained at lower SoC)That £100 you saved is tax free. A higher rate tax payer is going to have to earn £200 to pay £100 of electricity bill ... There's ROI and then there's Man Maths
Pisses me off that installers don't offer that ... surely its an upsell opportunity? ... even if they don't want to do it themselves there must be some mucker they could find locally and do a back-scratch with <sigh>
If a bit of API programming is within your ken? then you could do (based on my knowledge of PowerWall, I assume the rest are similar)
Battery > 95% AND PV generation >0 (or similar)
If so then charge car at X AMPs (X = based on PV Generation AMps less typical (or even "right now") household usage
If Battery falls 1% then reduce the AMPs by Y
If Battery rises by 1% then increase AMPs by Y (maybe when Battery > 97% then increase straight to 32AMPs)
If a cloud comes over you can choose not to react - and let Battery percent increase / decrease by 1% before you do anything ... or you could react (adjusting AMPs) according to what the Generation is each loop-iteration
Better to adjust amps frequently rather than stop./start charge (which will wear out contactors)
Again, assuming some fettling using the API, you could increase Battery Reserve to whatever SoC is at the time when car charging starts - that will prevent discharge of battery. (Battery API may have a "Don't discharge" option too)
For someone with savings this works better. The "saving" is then the return on investment - but its tax free, unlike regular savings - so likely to be well worthwhile converting Savings into PV-purchase - over 60's may get additional benefit too.
Drew57
Active ember
I recommend you check with the installer/inverter manufacturer to ensure that you purchase one with the ability to select block discharge settings. It makes little sense to cycle & fill the house batteries & then deplete them to charge the car batteries.
OneTinyFish
Member
Yes - the way energy prices have been going (consider last year on the IoM we had the cheapest energy in the British Isles) I thought it a safe bet prices would increase. They only needed to hit around 35p/kWh to make the loan repayment = the cost of energy and it hedges against further increases which for us are now certain.
Rang eon to chase up and when they said they had no installers in my area (SE!) I asked for my case ti be escalated to get a more specific response. They emailed back today with a ‘sorry it’s taking a long time but we have no ETA but hey you’ll be paying the locked in price’
Really frustrating - how do eon not have the ability to get suppliers in the south east? Or if necessary pay a bit more to unblock your customers waiting for an install
Really frustrating - how do eon not have the ability to get suppliers in the south east? Or if necessary pay a bit more to unblock your customers waiting for an install
I imagine their order book is too full. Just go elsewhere, their prices are high anyway when you compare like for like.
I’ve been waiting since July last year. So with prices I’m not sure I’ll get similar but could try looking again. They quoted me £10800 for 4kw solar and 9.5kwh Givenergy battery (plus AC inverter as I already have one array so the battery can take from both). 0% over 3 years too.
Chimpy McChimp
Member
It does seem good. My quotes for a 5.2kw system and 9.5kw givenergy battery plus install is around 15k (including bird protection) I got several quotes and they all came in around the 15k mark.
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posted this in other tread but still relevant I think.
I did my man maths today.
I took the high usage day where I consume above average of my usual consumption and will need 50 kwh in total to charge my car.
off-peak let's say 50 kwh
peak - 12 kwh (washing/drying during the day (help me...), teenage daughter forgets the towel rail on (face palm) and so on...
with this in mind, if I had EVERY SINGLE day whole month, it would cost me now 10.51 gbp a day / 315 a month.
If I offset all this with solar and batteries, then my daily cost would be ~4 gbp and up to maybe 120 gbp a month (car and batteries at offpeak rate, and all dayly usage is covered by solar/batteries
If I take financing for solar installation, with current banking rates and such, it would be ~220 a month for like 13 kilo pound cost of system..
so in such terms I would be almost break even on a month.. otherwise I see this as for 5 years I would be paying ~220 month in order to save ~80 a month. so -140 off the pocket as "investment".
it is a lot of money in general... 8000 buys a lot of electricity :/
is there anything I am missing here?
I did my man maths today.
I took the high usage day where I consume above average of my usual consumption and will need 50 kwh in total to charge my car.
off-peak let's say 50 kwh
peak - 12 kwh (washing/drying during the day (help me...), teenage daughter forgets the towel rail on (face palm) and so on...
with this in mind, if I had EVERY SINGLE day whole month, it would cost me now 10.51 gbp a day / 315 a month.
If I offset all this with solar and batteries, then my daily cost would be ~4 gbp and up to maybe 120 gbp a month (car and batteries at offpeak rate, and all dayly usage is covered by solar/batteries
If I take financing for solar installation, with current banking rates and such, it would be ~220 a month for like 13 kilo pound cost of system..
so in such terms I would be almost break even on a month.. otherwise I see this as for 5 years I would be paying ~220 month in order to save ~80 a month. so -140 off the pocket as "investment".
it is a lot of money in general... 8000 buys a lot of electricity :/
is there anything I am missing here?
Rooster6655
Active Member
If the system costs £8000 and it is now saving you £80 a month, then the return in the first year is going to be £960 per year or 12% which seems like a great return. Then if you are financing you can factor in the APR and deduct it from the 12% figure.
Rooster6655
Active Member
Based on your figure of £80 saving a month at 13k the return rate goes down to 7.38% before finance costs, if you have access to a good finance deal at a good rate it is still worth considering. There are of course many factors that could affect the return and how long it takes to pay itself off but its interesting how the usage cases can affect the savings when combined with IO!
RedMod3
Member
Generating 8.2kW while charging the car and topping up my PowerWalls. Our electric bill for today is 79p (we are all electric and no gas). Yes, the business case supports our setup. I still feel power costs will rise and a non-financial benefit of PWs is power if/when the grid fails
I think this is where Tesla are missing an opportunity. Why don’t Tesla start selling a battery add on with no inverter ? You would not need DNO approval. Yes I know it would only charge / discharge at a max of 5 kw but look at all the comparisons on the market now 3.6 / 5.0 inverters and add as much battery capacity as you need or can afford ? This is a market they are going to miss out of and more so in the future . I would like another powerwall but my DNO would not plus my current 5 kw output is fine but would love more battery capacity.
