Solar - what do I need to know?

akendall1966

What's the hot water system. if you have a hot water tank consider a diverter to use excess energy to heat water.  A 200l tank needs about 15kw of energy to heat from 20c to 70c. Ok gas is cheaper than electricity but costs more than export rates and compared to 15kw of batteries a tank and diverter is peanuts.

jo_sil

Simple advice from me - get your panels pigeon proofed alongside installation! I have spent a fortune on roof repairs and  retro fitted pigeon proofing - the mess, noise, damage and upset to neighbours these birds have caused has been a nightmare. There were 22 pigeons under the panels when I finally got it sorted!

Alnat1

Find out as much as you can, ask lots of questions on here about anything you don't quite understand.

Use the PVGIS calculator online to see how much this roof might generate for you.

Nickvale

I second the hot water heating diverter. My hot water is gas based, but there's a tank which has an electric immersion heater. I set the gas flow temperature to about 60 degrees, the immersion heater to 90 degrees, and the gizmo (Apollo Gem) diverts power I'm generating but not using to the heater. From March to November I use barely any gas at all.  

EssexHebridean

@screwdriva - yes, that makes perfect sense. Not sure I'd feel too comfortable having something literally over my head that was from some sort of unknown and dodgy brand anyway, to be honest! 

akendall1966 said:

What's the hot water system. if you have a hot water tank consider a diverter to use excess energy to heat water.  A 200l tank needs about 15kw of energy to heat from 20c to 70c. Ok gas is cheaper than electricity but costs more than export rates and compared to 15kw of batteries a tank and diverter is peanuts.

 & @nickvale No hot water cylinder in the house we're currently hoping to end up in, and probably nowhere sensible to locate one either to be honest - we currently live in a flat with an immersion and I have to confess one of the things I am most looking forward to is waving it goodbye!  

jo_sil said:

Simple advice from me - get your panels pigeon proofed alongside installation! I have spent a fortune on roof repairs and  retro fitted pigeon proofing - the mess, noise, damage and upset to neighbours these birds have caused has been a nightmare. There were 22 pigeons under the panels when I finally got it sorted!

Now this is not something I'd even have thought about - so thank you! Duly noted!

Alnat1 said:

Find out as much as you can, ask lots of questions on here about anything you don't quite understand.

Use the PVGIS calculator online to see how much this roof might generate for you.

I think you can safely assume that there will be lots of questions! - and the calculator is now found and bookmarked. Thank you! 

Really appreciate all the input on this! 

Reed_Richards

EssexHebridean said:

No hot water cylinder in the house we're currently hoping to end up in, and probably nowhere sensible to locate one either to be honest - we currently live in a flat with an immersion and I have to confess one of the things I am most looking forward to is waving it goodbye!  

The thing about solar power is that you won't be able to use it all in summer when you get the most.  You can export it but you usually get paid a fraction of what you have to pay to import electricity.  So you can get batteries to store electricity or you can store the excess energy as heat, which is a lot cheaper than getting a battery although less flexible.  The cheapest means of heat storage is a tank of water.  Other types of thermal store are available which are more compact but cost a good deal more.    

EssexHebridean

Yes, unfortunately I really can't think that there will be anywhere to site a cylinder so I think this isn't a viable option for us. I do get that in the summer months we'd be losing a lot of what we generate back to the grid though, and of course that the flipside is then in the winter the opposite occurs.

One question that has just arisen as a result of a post elsewhere on here though - are we better in the first instance to put our money into a battery, and use an E7 type tariff to charge that overnight, using the energy from it during the peak rates? This is the first time I've seen anyone suggesting that with the way thigs are now, battery first, and panels to follow later is a good way of doing things, so I'm curious to know what the general feedback on that idea would be. 

Magnitio

EssexHebridean said:

Yes, unfortunately I really can't think that there will be anywhere to site a cylinder so I think this isn't a viable option for us. I do get that in the summer months we'd be losing a lot of what we generate back to the grid though, and of course that the flipside is then in the winter the opposite occurs.

One question that has just arisen as a result of a post elsewhere on here though - are we better in the first instance to put our money into a battery, and use an E7 type tariff to charge that overnight, using the energy from it during the peak rates? This is the first time I've seen anyone suggesting that with the way thigs are now, battery first, and panels to follow later is a good way of doing things, so I'm curious to know what the general feedback on that idea would be. 

You will get a variety of opinions on batteries. If it is a question of solar OR batteries, I would go with solar. It is difficult to predict how the peak/off-peak rates are going to change over the lifetime of battery ownership; the rates have changed a lot in the last 12 months and with more people load-shifting and charging cars/vans/lorries overnight, the rate difference may well reduce. At least with solar AND batteries, you have more options for how you use your energy and minimise costs e.g. E7 is cheap at night (when no solar) but expensive during the day (when hopefully you have some output).

yp70479

Re Growatt: I was told not to touch them with a barge pole!. They had a really bad reputation a few years ago, although they could have improved. I have 8 400W Trinia panels (5xSouth, 3XWest facing), a Solis inverter  and an AC3.0 unit and 8.2KW battery from Giv Energy. The most I have generated in Jan is about 4.2 kw - the least is nothing at all!. But in the summer months I can get up to about 18KW.
I would say look at how much electricity you usually use per year, but also get an idea of your base load - the stuff that is on all the time - take a meter reading before you go to bed and again in the morning and work out what you use per hour. Multiply by 24 and you know the minimum mount of electric you will use without variable appliances. Then compare both these figures to how much your array can output.
Also think about how much power you will use during the day - are you at home all the time, or out at work most of the day. Home aloners tend to be able to use more of their solar than people out at work who without a battery end up exporting a lot of their solar for a pittance! If you have an old fashioned water tank and immersion you can get a solar diverter to put the extra solar power to heat your water rather than exporting it.
People say that batteries are borderline cost effective but a lot depends on how you use them. If you are on a time of use tariff and your battery is big enough to see you through the day and evening if the sun doesn't shine, then you can effectively run the whole house off the battery at cheap rate, through the winter. I'm with Octopus, their Econmy 7 is more expensive than EDF, but their SEG export tariff is much better if you also take incoming electric from them - swings and roundabouts - so I import at 16p, but any excess I sell back. This can be a fixed rate of 15p, or if you like a flutter and have a battery with spare capacity you can sell back at a variable rate at peak times (about 25p now, but I have had £1.86 per kwh before Christmas) - see Octopus Ougoing Agile tariff.
Try to work out the size of the roof area to see how man panels you can fit on (all installers will do this when they quote, but there's nothing like being prepared!). You can use something called "Easy PV" to get an idea of how any panels you can fit on. You also need to think about things like chimneys, TV aerials and vents which may cast shade as this can reduce the efficiency of a whole string of panels , even if only one is shaded. There are ways round this (micro-inverters on each panel). A lot of installers use a wholesaler called "Midsummer Wholesale" you can go on there and get an idea of what panels and batteries cost, which will help when you come to look at quotes (Segen is the other popular wholesaler but I don't think they publish prices). Whe people offer quotes make sure they include the cost of electrical work and scaffolding etc.
The brick shed sounds a good idea for the inverters and battery - you can put them outside if they are IP65 rated. Mine are outside on a west facing wall, but your choice of kit is wider if you can keep them undercover. You can put them in the roof if the battery is small (mine weighs 90kg so that was a no-no), but you need to think about how hot it can get up there, as above about 40-45 'C they aren't too happy.
OMG - just seen how long this post is - Apologies, but have fun with your homework!

yp70479

Oops nearly forgot - when they install they need to leave a minimum of 30cm from the gutters and ridges to reduce potential windlift.