In roof solar panels for roof tile repair/replacement

mjheathcote

Centenary Club
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In general if you go solar they advise you to get solar water heaters and gas cooking as those are two large electricity consumers so ideally you need to take those “off grid”. You would need a huge battery system to be able to run the house plus heating plus cooking.

We have regular “load shedding” which means we get cut off for 2.5 hours up to 3-4 times per day and with my 20 250W panels and 16 Lead acid batteries (10KWh practical capacity) we can manage that as the batteries charge up after each 2.5 hrs cut off if it’s at night. During the day the solar system will hack it with only very limited battery use if we time the washing machine/dryer/pool pump. Lithium batteries are the way to go now as they have many more charge cycles and also you can run them down to 10% whereas Lead Acid batteries should not be used below 50% charge if you want them to last. Also panel capacity has more than doubled to ~600W so you can get away with less panels (or bigger capacity on the same area).

Not sure about 600w panels, my new ones are 400w, which I believe to be the current readily available norm.
 

mjheathcote

Centenary Club
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9,033
No mains gas option here so that's not an option, only looking to maintain the basic light and power heating and cooking we can do without for the short periods involved

The system once isolated from the grid runs the whole house, or should I say the fuse box.
So you can switch on what you want as long as all demand doesn't exceed the inverter max output kWh rating.
 

zagatoes30

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20,763
Oh and water pump being our only supply is direct via a well we need a pump to get any water.

Looks like it is something to look into
 

midlifecrisis

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16,102
I can see the headline now.

“Pilot blinded by glare off solar panels!!”
You may joke but it's already been investigated and safeguaded against.
Glint and glare studies are carried out on all new building being built with Solar PVs, glint in that incidental flash experienced by the pilot when the sun reflects off the PV temporarily due to time of day and position of the sun/aircraft. Glare is the more persistent shine. We then take into consideration how bright it would be and does it cause any damage from negligible to something akin to Arc-eye. Really it's not different from glass building and the reflections emitted from them.
 

mjheathcote

Centenary Club
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9,033
Solar system all up and running :)
I've a better understanding of the system now installed.
10-off 400w panels feeding into the 3.6Kwh hybrid inverter.
Why not 4kwh inverter?
This is standard practice apparently due to limit of 3.68Kwh that can be put back into the grid without permission.
Second system is a further 6-off panels 2.4kWh feeding into a 3kwh inverter. We could therefore add a couple of additional panels on the house gable end for early morning or late afternoon at a later date easily.
So we have two separate systems.
They talk to each other so with little demand from the house, the limit back to the grid is still 3.68kw
Both inverters report back to the Web with both Web based and apps.
You can analyse basically everything about the system, both combined and individually, with full history. Enough for any geek.
Presently with full sun, it's pumping out 4.23kw which is pretty good for 10am.
 

sionie1

Member
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1,310
Solar system all up and running :)
I've a better understanding of the system now installed.
10-off 400w panels feeding into the 3.6Kwh hybrid inverter.
Why not 4kwh inverter?
This is standard practice apparently due to limit of 3.68Kwh that can be put back into the grid without permission.
Second system is a further 6-off panels 2.4kWh feeding into a 3kwh inverter. We could therefore add a couple of additional panels on the house gable end for early morning or late afternoon at a later date easily.
So we have two separate systems.
They talk to each other so with little demand from the house, the limit back to the grid is still 3.68kw
Both inverters report back to the Web with both Web based and apps.
You can analyse basically everything about the system, both combined and individually, with full history. Enough for any geek.
Presently with full sun, it's pumping out 4.23kw which is pretty good for 10am.
So do you think the battery will become a purchase sooner now than previously thought?
 

mjheathcote

Centenary Club
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9,033
So do you think the battery will become a purchase sooner now than previously thought?

Our daily average consumption is 18kwh, based on yearly bills and records from our smart meter over the 7 days before the solar system went live.
The 10 panel primary array went live on Monday and for Tuesday and Wednesday we imported 9kwh instead of 18kwh.
Now we have all 16 panels our import should be less, for its capable of generating more so top up from the grid should be less when having high draw applications such a washing machine/dishwasher on etc. I'll find out of the next few days.
But based on the 10 panel, and 9kwh import, if this was battery sourced (which is currently easy to fill up during the day in 2 or 3 hours), at the current 28p a unit this is approx £1k a year. So a battery would be paid off in 5 years.
However with now the full 16 panels, our draw should be less, so payback will be longer. However payback for the solar panels will be shorter.
Too early after just a few days and we are in the summer too, but payback on the solar panels is probably 6 to 8 years.
I still feel that using excess for hot water generation would be more beneficial as effectively our gas cost has gone up 3.5x compared to our electric at 2x.
I certainly feel the cost expenditure is worth it for the panels.
When the Mrs hybrid arrives that can be charged during the day, they will be potentially further savings in electricity cost to charge, not to mention more than double that again in petrol savings. This would reduce the payback for the panels to more like 5 years or less.
 

mjheathcote

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9,033
Well pleased it has just 'maxed out'
With little demand from the house the system has been throttling back to the max 3.68Kwh back to the grid.
Decided to put the kettle on for some demand and both arrays have maxed out with still some feed back into the grid.
100813
Analysing the inverters, the 6-off 400w panels through the 3Kwh inverter is outputting 2327w from a potential max of 2400w, so 97% efficiency.
The 10-off 400w panels are simply limited by the 3.6Kwh inverter, so it's putting out its max rated power.
100814
So happy will a 6Kwh max peak available from the system as a whole.
:cool:
 

midlifecrisis

Member
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16,102
Being due south really helps. My 4kw system peaks at 3.5kW at 11am but I'm more ESE. Still I didn't pay for it and I'll get a £1k a year back for it. If only it was put in 2 months before...then it would be double.
 

ScottH

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216
How’s everything looking now you’ve had it a bit longer? What do you get on a typical British day, overcast etc.?
 

mjheathcote

Centenary Club
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9,033
How’s everything looking now you’ve had it a bit longer? What do you get on a typical British day, overcast etc.?

See below, the yellow is what we used, the grey is what we exported, out of the total produced.
We are currently exporting way more than we use presently, it is the summer months remember.
We really need to utilise more either with battery storage, water heating, or EV car.
We would then produce more because the system is currently throttling back under low demand to limit feed back to the grid to 3.68 kW, when we are capable of 6 kW.

104992
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mjheathcote

Centenary Club
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9,033
Interesting thanks

With the rising electricity costs it does make more financial sense.
When we were paying 12p per kwh the payback was too long.
With the current rises, the payback time has been slashed in half, and it will reduce further as the price cap increases.
It is making more financial sense to now look at battery storage too now, so we draw very little from the grid on overcast days with peak demand, and to cover overnight usage.
In the deep winter months the option of charging the battery on off peak tariffs.
 

mjheathcote

Centenary Club
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9,033
It's a year with solar panels, and I've crunched the numbers.
We have saved £1,044 in electricity costs over the last 12 months due to the reduced import from the grid.
With the amount we have exported (we have no battery storage), a further saving of £526. So in total a saving of £1,570 per year.
The install was £9,620 so a payback period of 6 years and 6 weeks!
This will go up if the electricity costs drop, but the payback period is nicely within my original estimated 6 to 8 years.
This has greatly helped with our export payments with Octopus, currently 15p per Kwh exported.
Blatant plug referral code for Octopus:
So very pleased we made the decision to go with solar when the opportunity was made available to ourselves :)
 
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RodTungsten

Member
Messages
562
Still waiting for our 10kWh battery. Cables all in but delayed once again (myenergi Libbi). Currently dumping excess into the immerser and underfloor heating but it pains me to see kW going back into the grid. Car takes a good deal now as net surplus is regularly above 1.4kW (level required to wake up the charger).

One day I will sit down with Excel and all the numbers and see what the true payback is rather than a finger in the air estimate. Our FIT is going to change as well I understand.
 

mjheathcote

Centenary Club
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9,033
wack a 10kw battery on it
Calculation isn't as straightforward now we can get 15p sell back to the grid. It was on average only 5p/kwh a year ago.
For a quality battery system the cost was around £1k per Kw, maybe a little less now but pushing up to the cost of the original install!
We are all battery ready however, I need to check on current costs.