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Solar PV and add ons...

I'm sure that there have been huge strings of discussion on this but can't find much very recently - so apologies if i'm revisiting old stuff...

We are looking at solar PV and have had visits from 4 different companies... waiting for the quote from no 4. Two of them have told us that we couldn't fit a 4kWp system on our south facing roof and so have quoted for systems of 3 or just over. However we get the impression that those two companies who quoted for the smaller systems are selling what they have off their shelf and possibly not able to give us a quote for what is available from the whole market...

Based on assumptions about what size of system we can accomodate the opinions on whether or not an I-boost device would be worth it also appear split. (As I understand it I-boost uses any excess electricity to fuel the immersion rather than our current boiler fuel - oil). One of the reps (quoting for a 3kWp) felt a boiler management system would be a better option as we wouldn't have enough spare electricity to make it worth the IBoost. (Our annual use last year Oct 12- Oct 13 was 4500KWH)

At the moment we feel inclined to try to get the biggest system we can - however I am a bit concerned that the chap who quoted for that system told me that the FIT tarrifs for post March hadn't been released - when the smallest amount of research reveals that they clearly have!

We are awaiting the fourth quote which (judging on the impression we were left with by that rep) will be based on a 4kWp system.

Obviously we need to await that fourth quote... and do an awful lot of quzzing and question asking... but it would be interested to hear initial thoughts. At the moment this is all speculative. It probably won't happen if I don't get made redundant and consequently don't have a lump sum to invest... But if I don't get redundancy I do wonder if we should be finding some way of investing in it anyway. The potential long term financial return, particulalry the lower bills and the ethics are appealing!

Beware those offering you what you want (4kWp) when other say it wont fit. They could be doing this so they get the job & then on the install will apologize & say only a 3.?kWp one will fit. This has happened rather a lot. I bet none actually measured the roof. If you measure it remember that you need about 1 foot all the way round the edges kept clear.

Yes you can get PV that is more efficient so you get more kWp per m2 but it does cost more as well.

Re the Iboost or similar, are you at home all day so can maximize the usage of the PV power when it is made? If not then one will save you money. You might need to reduce the wattage of the immersion but that will depend on your base load.

Also of note is that you cant actually have a 4kWp system without getting permission from the DNO BEFORE installation. You are only allowed 16 amps worked out at 230v so 3.68kWp is the norm. Then you tell them after its installed.

Have you done an analysis of your energy needs? I ask because solar hot water can be much more efficient than using solar pv to power an immersion heater.

If hot water is your primary need then a split system or even solely solar hot water may be a better investment.

Thanks folks.

Both the reps I saw (OH saw the other 2) measured the roof (or appeared to do so - they certainly had measurements written down...) be interesting to see if their roof dimensions match each other... wasn't something I thought to question at the time...

We did get 2 quotes from one of the reps who reckoned we couldn't do 4kWp. She gave us one for lower kwp panels but with a higher efficiency guarantee and a more expensive quote for higher kwp panels but lower efficiency... didn't seem much to be gained from the more expensive panels in view of the efficiency issues.

No one has mentioned DNO permission for a 4kWp system thanks Smile

It's difficult to know whether or not I'll be in all day in future... I could be if a job doesn't appear Confused

Good point on energy needs analysis... Maybe half and half would be an option. One of the reps that my OH saw (the one we're still waiting for a quote from) seemed to be up on this. At the moment about 3/5 of our energy spend goes on oil which does CH, Hot water and occasional cooking... in the summer just hot water really. So getting our oil dependance down has to be a biggie in the long term for us. But I'd rather not give up our 10 year old Redfyre range completely... it's at the heart of the house/kitchen. For the price of the I boost (I was quoted 350 by one and 500 by another) It did seem quite a cheap "add on".

Will be very interested to see what comes back with the remaining quote...

I had one company offer me a quote based on their having measured the roof on Google Maps Rolling Eyes
I declined.

Have any mentioned that you need an EPC doing & get a D to be on the higher rate FIT?

VP, have you recently done the financial numbers on the two methods of water heating?

Last time I did it PV was still the most cost effective especially with the uncertainty about the RHI.

VP, have you recently done the financial numbers on the two methods of water heating?

Not for a long while. Back then solar hot water was the clear winner but as solar PV prices have plummeted by comparison it could as you say. There are a lot of variables to take into account, as you know, including efficiencies during periods of low solar intensity, usage patterns, and FITs.

We only have solar PV but our FIT is much higher than the import cost per unit.

Thats the thing with FITs & using the spare power & not exporting it.

You get "paid" for it twice. Once via the FIT deemed / un-metered 50% of total produced export & second by not paying for the water heating.
Jam Lady

We have a solar hot water system. Very happy with it, especially in summer when otherwise the boiler would be running to heat water just sitting in the storage tank. Sunlight on panels heats glycol which transfers heat to water. Even in cold weather. Does shut down in single degree Fahrenheit temperatures.

Our heating is propane fueled boiler, sub-floor radiant heat plus wood burning stove (and are we burning through wood this winter!) Cooking is also propane fueled range.

Yes they have mentioned the EPC and D rating requirement. Most seem to cover this within the price of the quote even though it is obviously supposed to be an "independant" assessment. So even if it is contracted out I do wonder...

So three out of the 4 companies that have quoted for us have used PV Sol software to supposedly assist in producing the "best" set up however they are all so different! Clearly it depends on what data is being fed into the model! Can't believe it is so different for the same house.

The inverter issue is interesting... We need to use two rooves, have a chimney casting a shadow, as well as some shadowing from one roof. One company has suggested all panels with mini inverters, another has suggested a mix of both mini inverters and a string inverter and the other two appear to have gone with 2 string inverters.. the mini inverters obviously more expensive but perhaps worth it for the increased efficiency of the system?

Goodness knows... started writing lists of questions!

I had hoped that the last of the quotes would be in but they seem to be faffing around a lot and keen to get an idea of what we have already been quoted. It was also suggested that the FIT drop to 6.6p in April - when it's already been published on the ofgem site as 14.38p... which rather raised my suspicions on the knowledgability or trustworthy front!

Some serious analysis required!
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