Has anyone used Open Energy Monitor to keep an eye on electrical power use? Our setup isn't straightforward (incoming supply to one distribution board, Solar PV to another that isn't easily linked to) so off the shelf PV monitoring probably won't work...

@ken, welcome to the forums. No, I haven't even heard of Open Energy Monitor, but I do like new products and will do some reading tonight.

@editor Hi Mars, Happy reading 😀  There is a lot!

I was thinking of putting an emonPi on the panel where the solar is (as thats where my networking kit lives too) and adding an emonTX to the main panel to measure consumption and monitor water pump usage (and anything else I want to investigate)  🤣 

I've generated 33,725kWh over 9 years or 3,747kWh per annum.  From a 4kW system.  Worcestershire.  Exactly South facing.  44 degree sloping roof.  No shade.  16 Hyundai panels and a 4000 TL SMA Sunnyboy inverter

@julianc I'm trying to make a reasonable estimate of how much power I could generate from solar PV.

I've looked at solar PV before but now thinking again given the massive increase in electricity rates

If I read this right you are getting about 234kWh per panel per year?

I have a south facing roof, similar pitch, similar latitude (Oxon) but only have room for 9 panels - so about 2,100kWh, or just over £400 worth at current tariffs.

As a matter of interest are you able to break that figure down by month?

Mike

@mike-patrick I'd suggest you just use this website, it can calculate your generation. 

https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html

@batalto Thanks. Assuming Ive plugged the numbers in correctly that gives me a more optimistic estimate of about 3,000kWh pa. across 9 panels.

That is about 25% of my total kWh per year so very much worth doing at the current tariffs of 20p or more per kWh. With an installation cost of about £6k that's a 10% return.

Better than money in the bank at 0%.

Mike

@mike-patrick 

Hi Mike,

Let me first of all say that I am a firm believer in fully utilising solar energy to reduce energy consumption. Without wishing to appear like a wet blanket, I think that your estimate of 3000kWh per annum is extremely optimistic, it will probably be around 2000kWh from a 2.1kW system.

On top of that much of the generation will be in the Summer, when you may not be able to fully use it to reduce your electricity import. Obviously you could also install a battery storage system, but even this would only help reduce your overnight electricity consumption for part of the year.

First of all you need to assess how much electrical energy you use, when you use it and for what purpose. Then use the calculator, kindly provided by Batalto, to see what the estimated generation will be for each month of the year.

If my memory serves me well I think that you have stated previously that you have an ASHP, in which case you will be able to use more of the energy generated by a solar PV system, but even so you will not be able to use all of it and will export some which I believe can qualify for a payment of 5p per kWh.

Personally I use the generation from my 4kW solar PV system to provide most of our hot water requirement from Spring through to Autumn and also to reduce our gas consumption by 20%. After installing an A2A ASHP earlier this year the solar power provides further help with both heating and cooling.

I hope that I have not put you off getting a solar PV system, but thought that you should be fully aware of all the facts.

@mike-patrick Hi Mike, to help you understand the potential I think you need to also look at a battery system as well, as you can produce X amount of Solar PV but if you aren’t using it when the sun shines then you are not really benefiting from it fully. Here are some of the points that maybe help you understand what you could potentially benefit from making sure you get the absolute most value from your Solar PV array, firstly don’t just accept what the solar installer suggests for a fixed sum as they will buy in bulk and sell for as much as they can make, I researched my solar install to ensure that I kept the benefit well into the 25 year life time, so I wouldn’t see much degradation of performance from my install over that time.  So things that you should pay a little extra for but will reap the benefits over time are as follows. 

1. Solar panel output size. Most panels are in the 300w size as that is what is cheap and which for you would produce 9 x 300w = 2700w potential, I chose the bigger output of 455w which if i had 9 panels would give me 4050w potential (my actual array is 12 Jasolar 455w panels which gives me a 5.46kWp (this is the peak performance it could potentially give me. Another thing to consider is the type Mono or Poly (Monocrystalline solar panels have the highest efficiency rates, typically in the 15-20% range. This high efficiency rate means they produce more power per square foot, and are therefore very space-efficient. ... They perform better than similarly rated polycrystalline solar panels at low-light conditions.). I went for mono and the difference in price is very little. 

2. Then there is the inverter you can use String or micro inverters, while you can just google String v Micro inverter the thing that I discovered is that the micro inverter in my opinion and i suggest the rest of the internet is that they are better due to several reasons, 1. If you have a string inverter then if part of the one panel is shaded then the entire panel array of 9 panels would be degraded by that one panel, individual micro inverters only affect the single panel. There are options to mitigate that but then it adds to the price, and if it goes wrong on a string its all the panels affected rather than just the individual micro inverter. Micro inverters appear to have a longer life span and while more expensive they react quicker than string inverters so allow you to maximise your solar production. I use Enphase MicroInverters IQ7+ So 12 of them for my 12 panel array. 

3. Inverter. This is what will turn the Solar PV into actual power, mine is a PowerLux AC ESS which gives me a total of 3.6kW  of power to provide for my home electric consumption. Now what that means is everything below that figure could potentially be powered by solar alone but if for example i switched on an electric shower at 8kWh then i would need to obtain another 4.4kW of power which will come from the grid (8kW minus Solar PV or 3.6kW leaves 4.4kW). Now I know that my actual array can power more than 3.6kW and potentially i could produce 5.46Kw but then you start to have issues with the power companies and anything over 4kW requires more paperwork and that means more cost (it can be done but installers will say you are at the 4kW “fit and inform” limit where you just inform the Power Grid that you have fitted the array. If I’m honest with hindsight I would have fitted a larger inverter and just paid for the extra paper work, but if would have mean a larger Inverter at an additional cost so its all relevant and a trade off in the end. I also factored in the fact that your solar array will only have the “Potential” to produce what it can to its max in perfect conditions, solar panels even at the same wattage will differ (i have today one panel that’s produced 157watts and another one that has 146watts which is 11watts difference on the same clear roof, over time it makes a difference). Finally the panels will degrade in performance over time so on average they degrade 0.5% per year so by year 20 your panels will be at around 90% productive than they are today. Solar panels will still produce energy past that point but in 25 years the technology will have moved on that it would be cost effective to replace them with much more productive panels. I because of my over specification and limit (Clipping) at 3.6Kw shouldn’t see any reduction in my solar production results. 

4. Batteries !!!! Okay this is often a hotly debated subject as in should you or shouldn’t you get batteries to augment your solar array, some people say the inclusion of batteries makes it more costly and less of a return on your investment but I have always looked at it like this. When you buy a new kitchen for your house you never really look at it from a ROI point of view you simply get it as you want a new kitchen, the benefit of Solar is you can actually track a benefit so people have been looking at it that way from day one to justify the purchase. I like the idea of using less energy from the grid, doing my bit for green energy and obtaining a benefit for money that I’ve spent. Now the simple fact is Solar works best when the Sun is out to play 🙂 but the vast majority of us are potentially at work during the the better part of the day so if we are maxing out on solar production during the time we aren’t at home then we are producing but not using that potential ! So how do we time shift that to a time when we are back in the house and want to use that free power ….. BATTERY Storage ! I have a 4.8kWh system which is great for powering after the sun goes down and adding to the maximum amount of electric i can provide to my house at one time so that 8kW electric shower is now powered by the solar and battery to the potential of 6.5 which means i would only need 1.5kW from the grid 🙂 Battery in my head just makes sense to be used when you need it most and to utilise the times when you are not consuming all the power that your solar is producing. I would benefit every further if I had my smart meter installed (still waiting but COVID has caused delays) i would have benefited from cheap over night charge tariffs and export tariffs. 

In summary and I’m sorry for the long text but I tend to want to explain my experience in full, I think a solar PV with battery is the way to go and I wish you luck in your journey 🙂 

So far this year since Feb 1st till now (7 months and 5 days) I have produced 3237.5kWh of Solar PV, my consumption of Electric has been 3337.2kWh but I have only imported from the grid 1635kWh so I provided through my batteries and my solar PV a total of 1702.2kWh which is on average of 21p per kWh about £357 saving. 

@boblochinver personally I decided on string rather than micro inverters on my panels. The main reason was efficiency and cost. You get maybe 1 or 2% more from them, but they cost quite a lot when you add them all up. Payback is really limited. String made more sense as we are in no way shaded and the cost was much more effective.

@batalto agreed but over time they more or less level out on cost and as an ex-army guy I like to mitigate potential single points of failure. Micro inverters are typically more robust and last longer than a string inverter. when they do fail I only have to replace the one that's broke

@boblochinver honestly I reckon I could make a system very cheaply these days. Get the panels of gumtree, pick up a used hybrid inverter and the batteries off AliExpress. I think I could make a 10kw array with 10kwh of batteries for £4k (hardware)