Solar panels and battery - any real world reccomendations?

BUDFORCE said:
Web portal. I have the app as well but I just use that to keep an eye on it.

I don't have home assistant.

I suspect the 2.6kwh is because it's cold, but honestly no idea really.

At least it seems to have gone back to eco mode after the timed charge.
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Have you checked its not a general connectivity issue? Pretty sure there was a thing that came out recently about updating the dongles if you have wifi problems.

The wifi hardware they use on pretty much all IOT devices are utter ****, recommend hard wiring where you can but I'm not sure how easy that is on the older kit.
 
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just started to look into Solar Panels for home, doing lots of reading.

ive been on PVWatts site and let it measure our roof space, it says 5,228 kWh/Year, is this the max amount the solar panels can achieve?

So i need to look for an array that can do max 5228 kWh/Year and a battery to suit? any higher then it will be a waste?
 
lmfy2k said:
So i need to look for an array that can do max 5228 kWh/Year and a battery to suit? any higher then it will be a waste?
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Let me think about that, NO! Fit as much as possible, even potentially on roofs facing north.

You don't want to match what you use, you want to export as much as possible, as every kWh exported earns around 15p, thus you bank money for the winter when you don't generate much, and may even make profit, which in turns pays back the cost of panels even quicker.

You must use an MCS installer, as it makes getting paid for exports so much easier.

This year, not including today, I've imported £1450 of electric, and I've exported £1600 worth, take into account the payments from my FITS system and I've even covered my gas bill for the year, second year in a row my gas and electric has been negative.

Have a watch of this video

 
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lmfy2k said:
just started to look into Solar Panels for home, doing lots of reading.

ive been on PVWatts site and let it measure our roof space, it says 5,228 kWh/Year, is this the max amount the solar panels can achieve?

So i need to look for an array that can do max 5228 kWh/Year and a battery to suit? any higher then it will be a waste?
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what @Ron-ski said, fit as many panels as will physically fit on your roof, add some battery stage if you have any money left.

There is no 'sweet spot' for panels, the more you have, the more money your system will generate, if any installers tell you otherwise, they are wrong.

On the other hand battery storage absolutely has a sweet spot and there are diminishing returns the bigger you go. 60% of your daily usage is a good starting point, 80% is ideal and beyond that hits diminishing returns very quickly.
 
Another point, make sure you get a decent size inverter, bigger models are not much more expensive, and it means you can charge batteries more in the off peak periods.
 
Strictly speaking the Go tariff is for EVs, but there are no checks.
I don't have an EV, but I've used the Go tariff for the last two winters, and Flux in the sunnier months.
 
b0rn2sk8 said:
On the other hand battery storage absolutely has a sweet spot and there are diminishing returns the bigger you go. 60% of your daily usage is a good starting point, 80% is ideal and beyond that hits diminishing returns very quickly.
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Yeah I agree with this.

I often thought about getting a second 5.2kwh battery but honestly I am not sure its worth it. The battery is mainly for the smoothing.

During the winter there is very rarely enough sun to fill 5.2kwh plus normal home use, then on the flip side 5.2kwh during most days during the summer months is just about perfect as it'll just about last until the morning.

I know that isn't factoring pulling cheap overnights rates etc, I could probably use 8kwh more effectively, I honest think double up to 10kwh would be overkill.


On a side note, as we've been having these power up sessions, you know how I was saying the battery only charged 2.6kwh to 100% the other day.

Well yesterday 3.9kwh, and today 4.10kwh... that factors in a little overnight period where it stops the battery going below 4% overnight, but even so, its what you would expect, so in that respect, I am happy. But then it makes you wonder why it only charged 2.6kwh the other day?
 
But a larger battery can allow you to run on 8.5p (or possibly cheaper electric) all day in the winter, as long you can charge it in the cheap period, I always export my excess battery at 15p kWh gradually from 19:30 to midnight. So there is that to consider.
 
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Ron-ski said:
But a larger battery can allow you to run on 8.5p (or possibly cheaper electric) all day in the winter, as long you can charge it in the cheap period, I always export my excess battery at 15p kWh gradually from 19:30 to midnight. So there is that to consider.
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This is definitely true but you do need to run the numbers when paying commercial rates for batteries and the marginal rate is only 6p once you factor in round trip losses.

In my mind the best case scenario you save 16p/unit (25p peak rate less 8.5p import less efficiency loss) for 6 months of the year and benefit from 6p exports (15p export less 8.5p import less efficiency loss) for 6 months of the year on a 5kwh battery.

(16p*5*182) + (6p*5*183) = £145 + £55 = £200 per year saving.

In reality I think it will be less than that because you are probably doing enough solar for 7 months of the year to get you through on the existing battery and then you'll not be fully utilising the battery for self consumption in some of the other months. You'd need to run the numbers against your own usage profile and expected consumption.

You would then need to compare any return to what you could get investing the money, putting it in an ISA or paying off any existing debt (e.g. mortgage).
 
b0rn2sk8 said:
This is definitely true but you do need to run the numbers when paying commercial rates for batteries and the marginal rate is only 6p once you factor in round trip losses.

In my mind the best case scenario you save 16p/unit (25p peak rate less 8.5p import less efficiency loss) for 6 months of the year and benefit from 6p exports (15p export less 8.5p import less efficiency loss) for 6 months of the year on a 5kwh battery.

(16p*5*182) + (6p*5*183) = £145 + £55 = £200 per year saving.

In reality I think it will be less than that because you are probably doing enough solar for 7 months of the year to get you through on the existing battery and then you'll not be fully utilising the battery for self consumption in some of the other months. You'd need to run the numbers against your own usage profile and expected consumption.

You would then need to compare any return to what you could get investing the money, putting it in an ISA or paying off any existing debt (e.g. mortgage).
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theres too many variables just to be able to do basic math to make it add up..... theres also the green side of everything, not everything needs to have a monetary value on it.
 
Same here, far too many variables for me to compute, so I didn't bother, all I do know is that our yearly costs have been negative two years running, that's circa £2500 saved two years in a row, probably more as we're in profit each year as well.

I have some debt, interest free credit card, money to pay that off is in premium bonds. Mortgage I could easily clear (we're mid fifties so not much on it as previously overpaid with less than three years to go), but I'm better off putting it my pension, return last year was circa 25% on that plus the tax rebates (I think)

I'm hoping to retire in less than three years (if the markets continue as they have), electric is sorted, ASHP this year (gas will go) and an EV, this should get our running costs pretty low, so long as nothing goes wrong.

Yes, I've spent a small fortune on our system, but it will have a long life, same as the EV, and the ASHP, all these will bring monthly costs down for retirement, which means more money stays invested and makes more money, or more holidays :D

PS. We're comfortable, but certainly not well off, and we've worked very hard to get where we are.
 
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b0rn2sk8 said:
EDIT: I'm going to attempt to spreadsheet what the savings where and see where I come out.
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I think this is more appropriate to this thread than the production figures thread and may help those who are undecided on solar.

My system was installed on 11/01/2024, my full set up is 23 panels split 14 west and 9 east, the 9 east*, a 13.5kwh battery, an EV and a 6kw Daikin heat pump (installed 17/4/2024). *A few east panels are shaded by my own roof (L shape house) in winter months.

Our total energy consumption was 8893kwh electric and 4828kwh gas for the year. The gas was fully disconnected on 17/4/2024.

My total bill for the year came to just £108.28, this includes gas up to 17/4/2024 which was £359 and driving our Model Y 10,000 miles.

We imported 6605kwh and exported 5738kwh.

My savings for the year from the solar was: £1,891.33

This breaks down to:
  • solar self consumption: £624.45
  • solar export: £860.68
  • Solar to battery to house: £27.17
  • Battery time shifting: £379.03

I don't have data from what the heat pump is saving, some of it is captured above in the form of solar self consumption and grid charging the battery. However a load of it is from time of use tariff savings which I don't have the data to come close to a number. I don't run the heat pump for maximum efficiency, I run it for lowest cost based on the IOG tariff. Despite this I've got a COP 3.4 since installation which is not bad considering.

I'm ranging between 30% and 100% off peak (7p/kwh) looking at some sample days. 100% being when it is only doing hot water and 30% which was my highest consumption day at 27.31kwh (21/11). Typical daily consumption over December was 12.5kwh and 40%+ off peak.

There is also the obvious saving of the £100/year on standing charges and I expect my bill to be negative next year.
 
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b0rn2sk8 said:
I think this is more appropriate to this thread than the production figures thread and may help those who are undecided on solar.

My system was installed on 11/01/2024, my full set up is 23 panels split 14 west and 9 east, the 9 east*, a 13.5kwh battery, an EV and a 6kw Daikin heat pump (installed 17/4/2024). *A few east panels are shaded by my own roof (L shape house) in winter months.

Our total energy consumption was 8893kwh electric and 4828kwh gas for the year. The gas was fully disconnected on 17/4/2024.

My total bill for the year came to just £108.28, this includes gas up to 17/4/2024 which was £359 and driving our Model Y 10,000 miles.

We imported 6605kwh and exported 5738kwh.

My savings for the year from the solar was: £1,891.33

This breaks down to:
  • solar self consumption: £624.45
  • solar export: £860.68
  • Solar to battery to house: £27.17
  • Battery time shifting: £379.03

I don't have data from what the heat pump is saving, some of it is captured above in the form of solar self consumption and grid charging the battery. However a load of it is from time of use tariff savings which I don't have the data to come close to a number. I don't run the heat pump for maximum efficiency, I run it for lowest cost based on the IOG tariff. Despite this I've got a COP 3.4 since installation which is not bad considering.

I'm ranging between 30% and 100% off peak (7p/kwh) looking at some sample days. 100% being when it is only doing hot water and 30% which was my highest consumption day at 27.31kwh (21/11). Typical daily consumption over December was 12.5kwh and 40%+ off peak.

There is also the obvious saving of the £100/year on standing charges and I expect my bill to be negative next year.
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Thanks for the detail, looking to put in solar and battery this year similar to your build. Certainly helps convince the wife the conversion does work.
 
With a heat pump it's a no brainer really. As a test i left my house at 19.5 degrees yesterday. It pulled 22kw in 24 hours at below zero. With ovo there is a 30% heat pump discount as well. If you bank a kw of solar via export in the summer then it covers the winter on par. Payback is around 8 years for heat pump, battery and solar. If you have the capital it is a simple choice
 
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SpeedFreak said:
With a heat pump it's a no brainer really. As a test i left my house at 19.5 degrees yesterday. It pulled 22kw in 24 hours at below zero. With ovo there is a 30% heat pump discount as well. If you bank a kw of solar via export in the summer then it covers the winter on par. Payback is around 8 years for heat pump, battery and solar. If you have the capital it is a simple choice
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What is you insulation of your house like?

Also what temp were radiators on or flow rate or whatever it is called and how long?
 
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TNA said:
What is you insulation of your house like?

Also what temp were radiators on or flow rate or whatever it is called and how long?
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My design temperature is 50C @ -2C outside temperature but it’s based on an overestimated heat loss because my actual heat curve is set at 45C at -8C outside temperature.

So even now it’s 0C outside, my flow temperature is only 39C. At -2, I’ll be at 40/41C flow temperature which is ideal for a retrofit.

Insulation doesn’t really matter, as long as your system design enables you to get a SCOP of ~3.6 or more, you’ll have equivalent running costs to your existing gas boiler at price cap prices. You can pay way less than the price cap for your electricity as we all know.

Electricity is 25.5p, gas is 6.2p so electricity is 4.11 times more expensive than gas. However gas boilers are not 100% efficient.

A very well tuned* gas system is about 90% efficient which gets you down to 3.7 times the cost. Except the vast majority of gas boilers are not very well tuned and in reality operate at a much lower efficiency. 85% is still a very prudent efficiency and you are down to 3.5 or a SCOP of 350% for your equivalent running cost. Of course you want to go higher if you can to reduce running costs.

Insulation reduces overall usage but that also applies to gas and it doesn’t change the equation or your ability to fit a heat pump**.

*well tuned means designed to a 50C maximum flow temperature (or below) like a heat pump also would be and has weather compensation based controls - hardly anyone has this set up.

**except where you live in a mansion where the heat loss is so large, the required heat pump is so big, you can’t fit it to a normal single phase electricity supply. You’d expect a property that big to have a 3 phase supply already anyway.
 
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TNA said:
What is you insulation of your house like?

Also what temp were radiators on or flow rate or whatever it is called and how long?
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200mm in loft, 120mm under suspended floor, cavity insulated. Bungalow is 120sqm. Flow is about 45 at present, but need to check the curve. Heating was on 24 hours as a test, but house was at temp.
 
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Anyone here tried octopus heatpumps? If so how was your experience?

Might get a quote from them.
 
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