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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
Your 4.5kw system will be peak, unshaded, south facing mid day output. 4.5kw is ~16A, so that's your max on the Y axis.
Throw a nice bell curve over that on the X axis and you have your ideal June day curve, with your 6A cutoff. So maybe putting current in between 9am and 3pm? Maybe 8 and 4? Not sure.
But that's June... Now a Z axis for over the year and that max mid day will drop right off. @RedMod3 above awesomely had some stats, showing about 1/5th power output for Jan to June. 1/5th of of your max power is only going to be 3A, at mid day, and you still have the X axis for the time of day to contend with. So by that bad math you won't really get a charge in the winter as you aren't getting over the 6A minimum (which is correct for the M3 I'm pretty sure).
That's really bad back of an envelope math - in particular monthly output != current supplied - on a really sunny day in or near winter you may crawl over the 6a to do some trickle charging, but its probably not going to win over a regular commute.
Also, at lower charge rates a larger % of your power goes to just running the car systems while it's charging.
Still helps in the summer when you likely do more mileage anyway, but it's not going to be year round free charging
.
It's the annoying thing with solar (which I'll hopefully get anyway), it's not really enough for a car, at least not year round, and production is 100% opposite (on a daily and yearly basis) of my heat pump reqs.
But it can conver a lot of everything else so still worth it given the way process are going. Unless my spread sheet is even worse than the above math I think pay back could be as low as 4 years just now! We have a big base load due to some IT stuff and I figure I can move a fair bit of other load to during the day of into an over night rate eventually.
Throw a nice bell curve over that on the X axis and you have your ideal June day curve, with your 6A cutoff. So maybe putting current in between 9am and 3pm? Maybe 8 and 4? Not sure.
But that's June... Now a Z axis for over the year and that max mid day will drop right off. @RedMod3 above awesomely had some stats, showing about 1/5th power output for Jan to June. 1/5th of of your max power is only going to be 3A, at mid day, and you still have the X axis for the time of day to contend with. So by that bad math you won't really get a charge in the winter as you aren't getting over the 6A minimum (which is correct for the M3 I'm pretty sure).
That's really bad back of an envelope math - in particular monthly output != current supplied - on a really sunny day in or near winter you may crawl over the 6a to do some trickle charging, but its probably not going to win over a regular commute.
Also, at lower charge rates a larger % of your power goes to just running the car systems while it's charging.
Still helps in the summer when you likely do more mileage anyway, but it's not going to be year round free charging
.It's the annoying thing with solar (which I'll hopefully get anyway), it's not really enough for a car, at least not year round, and production is 100% opposite (on a daily and yearly basis) of my heat pump reqs.
But it can conver a lot of everything else so still worth it given the way process are going. Unless my spread sheet is even worse than the above math I think pay back could be as low as 4 years just now! We have a big base load due to some IT stuff and I figure I can move a fair bit of other load to during the day of into an over night rate eventually.
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Oh yea, your input tariff is completely unhooked from your output - so you can move input suppliers to whatever is best for you and have solar and agile or go or EU etc. I'd need an actual spreadsheet to check, but you might be better charging at 5p/unit overnight and using your shoulder season solar for other things. I suspect charging the car at 6A is -that- inefficient.
A drop from 16A charging (blue industrial socket) to a normal 3 pin at 10A doubles the charge time despite only dropping 1/3rd the power. So you end up using much more electricity overall. Full blast overnight on a good rate might be better and dump the excess solar into your hot water via an Eddie (sp?) device.
A drop from 16A charging (blue industrial socket) to a normal 3 pin at 10A doubles the charge time despite only dropping 1/3rd the power. So you end up using much more electricity overall. Full blast overnight on a good rate might be better and dump the excess solar into your hot water via an Eddie (sp?) device.
I have 9.96 kW of panels plus a powerwall 2. In the full year of 2021 we generated 6.2MWh of solar mainly in the summer months. I am on the TEP in order to benefit from export of surplus energy at the same rate as I paid for importing as FIT no longer exists. With the increasing bills ie so far in my case from 8p per kWh to 11.11p per kWh this year to possibly 20-30 p per kWh later this year I will save more and more. If I could get a second powerwall I would probably change to Octopus GO as I would need to export less.
The full installation cost me £20k and this will be returned in about 6 years.
The full installation cost me £20k and this will be returned in about 6 years.
cryo
Member
My fit for the winter quarter was approx £50+a small amount for export from a 3.6KW south west facing array. I suspect you have been misinformed or do not understand the historical fit prices.
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cryo
Member
The local DNO use a diversity factor working on the principle not every shower, kettle, or appliance will be on at the same time to size the local distribution system unfortunately this is not the case with solar which will all be on peak production at the same time on all local installs and possibly constant max export for a number of hours which can lead the risk of overloading the local transformers/cabling. A similar thing happens when BEV's become the dominant method of transport and the local DNO will either refuse permission for chargers or through government law take control of all EV chargers. The DNO charger control will happen sooner than people think.
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RedMod3
Member
No, but make sure you get 3 quotes. I've had a ridiculously crazy £4,800 quote for a 4-panel 1.5kW system on a bungalow!
RedMod3
Member
Agreed, here are our cash receivables by month for a 3.6kW inverter. The first col is the total.
cryo
Member
Generation tariff 56.03p per KWh-export tariff 3.95p-per KWh- assumed export 50% of production- index linked.
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RedMod3
Member
True, but even on Octopus GO rate at 15.59p during the day, I'm avoiding £500 a year in electricity bills, and when the day rate doubles, my avoidance will be £1,000 a year. Now, I'd say panels are worth it if you live in the south and don't have too much shading; we have a little shading.
SpareHeadOne
Member
If a Powerwall is being considered then it's worth noting that a recent app update allows you to specify your import and export prices so that the system can decide if it's more cost-effective to store excess solar or export it. Not relevant for anyone on one of the old "deemed" tariffs, but definitely useful for anyone with metered exports.
cryo
Member
Even in the north if the rate doubles to 30p you will save at least £500 a year off your bill+ any export on a 3.6KW system. System faces SW and generates 1800-2000KWh a year North East coast.
Thank you @Avendit & others.Your 4.5kw system will be peak, unshaded, south facing mid day output. 4.5kw is ~16A, so that's your max on the Y axis.
Throw a nice bell curve over that on the X axis and you have your ideal June day curve, with your 6A cutoff. So maybe putting current in between 9am and 3pm? Maybe 8 and 4? Not sure.
But that's June... Now a Z axis for over the year and that max mid day will drop right off. @RedMod3 above awesomely had some stats, showing about 1/5th power output for Jan to June. 1/5th of of your max power is only going to be 3A, at mid day, and you still have the X axis for the time of day to contend with. So by that bad math you won't really get a charge in the winter as you aren't getting over the 6A minimum (which is correct for the M3 I'm pretty sure).
That's really bad back of an envelope math - in particular monthly output != current supplied - on a really sunny day in or near winter you may crawl over the 6a to do some trickle charging, but its probably not going to win over a regular commute.
Also, at lower charge rates a larger % of your power goes to just running the car systems while it's charging.
Still helps in the summer when you likely do more mileage anyway, but it's not going to be year round free charging
It's the annoying thing with solar (which I'll hopefully get anyway), it's not really enough for a car, at least not year round, and production is 100% opposite (on a daily and yearly basis) of my heat pump reqs.
But it can conver a lot of everything else so still worth it given the way process are going. Unless my spread sheet is even worse than the above math I think pay back could be as low as 4 years just now! We have a big base load due to some IT stuff and I figure I can move a fair bit of other load to during the day of into an over night rate eventually.
Personally, I only charge the car a couple of times each week, and commute c.2 days, so car will be there a fair bit ready to charge IF we get a sunny day. That might be rare in Winter (so it'll need a top-up) but in Summer sounds like it'll work well.
Installer visited today and seemed to think that would work well - big roof, south-facing and zero shade with 11 panel / 4.5kw system. He initially said we'd just do that and not do the usual water/emersion diverter, but then advised that for the extra c.£300 it was probably worth having both even if just for summer months....so think that's my plan.
Even if I end up saving £500 in electricity costs (across any appliances + car), and getting zero payments from the FIT that's fine by me. And seems like that's feasible for right now, let alone once the April price increase kicks in!!
cryo
Member
I don't think the government boffins understand what happens to compound interest over an extended period.
RichardTheKing
Member
I don't get how you can have a return in 6 year for £20k, how do you get £3333 return every year?
goRt
Active Member
"them" - that's all of those with electricity bills with the green levy on them - 2/3 of that is your FiT payment.
