Domestic Solar - would it pay me ?

Clive

Staff Member
Arable Farmer
Location
Lichfield
Currently renovating the farmhouse, it's not by the farm yard so this would be purely domestic use

about 100m from the farmhouse is a new 4000 sqft barn - one side of the roof faces directly south but is far enough away and out of sight to not be an aesthetic carbunkle !

what would the cost of a solar installation be that could provide the needs of the house ? (it's a big house circa 10k sqft) is there any financial case for building more capacity than the house will use for profit ?

is this all dependant upon feed in tariffs still or does it stand on its own 2 feet now financially ?
 

Exfarmer

Member
Location
Bury St Edmunds
Fairly certain that it would pay to have an install up to 10 kw, especially if you have either a swimmimg pool or air conditioning. If you have neither , i would suggest you plug your new Tesla in :)
Just joking
 

milkloss

Member
Livestock Farmer
Location
East Sussex
I was wondering the same as we put in a 13amp electric aga. It's got AIMS or whatever name they have for a useless power saving device but I can't help thinking a 30amp aga cooked up during the day on solar would've been a better option.
 

f0ster

Member
the present tariff is 4.36p from 1st of april and the export rate is 5.03p so if you generate 26000kwh from 30kw (which is easily possible) the production is 26000 X .0436 = £1133.60 you then get what ever you have produced (26000kwh) at 5.03p X 50% so 26000 x .0503 X 50% = £653.9 then if you can use as much as poss for example 80% usage. if you are paying 12p for your electric it is 20800kwh x .12 = £2496 the last bit you have to calc at what ever you are paying for your electric. a heavy user might only pay 8p but some of my customers were paying 16p, if you are using less than 80% then calc it at what ever usage you are having. the best way to gauge how many kw to install is to look at your electric bill for the year and install an amount to suit your bill so that you get full usage of the panels. but do not go above 30kw because above this you need an import/export meter fitted and there is often an annual service charge, below 30kw you do not need an import export meter so that is why it is better to stick below 30kw.

this is what I posted on another thread, if you are wanting solar on a domestic property at 100m distance first of all you are going to require SWA cable to feed this barn unless it already has power, but then if it has power already it will not do your house any good because you need to be connected with the solar on the property side of the meter to be able to make use of it.
as for how much solar to install it depends on the supply to the property. if you are domestic you will most likely be on single phase and as such you are only allowed to generate 16A without a grid connection, you can have more with an export limiter or a grid connection, (in scotland it costs £600 for a grid connection)
the cable size to feed 16A at 100M distance needs to be 16mm to prevent volt drop, (inverters require 2% volt drop max)
as for installing more than you need, the days of solar for profit are long gone, in order to make it pay you need to be using as much of what you produce as possible which can be difficult but there are ways for example there are devices that automatically divert any excess solar power generated to your hot water tank immersion heater so that instead of exporting it you are using all of what you produce, even on a cloudy day it works by only giving the immersion heater the voltage available so for example on a cloudy day it might run the immersion heater at just 80V, it will not draw from the grid only the solar. the going rate for 4kw of solar installed is about 6k more or less but you are also going to require 100m of SWA at about £6 a meter. and it has to be routed there some how. if you have the space a field mount might be better by the house and you can make sure it is directly south and at 36 deg. payback on a domestic install gets up in the 8 to 10 years.
 

f0ster

Member
if you mean install it your self it is not possible. there are a shed load of qualifications required to be able to sign it off and get the tariff as well as being a member of a professional body, even tho the tariff is not the best at the moment the cost of an install has came down a lot also. you can install it your self if you are not bothered about the tariff and as long as you are using most of it you should do ok, the cost price of a 4kw kit is about £2500 ish
 

f0ster

Member
I have a customer who has 5.5kw running off a 4kw inverter, by looking at the inverter max input voltage/current he was able to increase the input voltage/current to the max inverter spec with the approval of the inverter manufacturer.
 

f0ster

Member
electricity north west (ELNW) have come up with a cunning way of extracting money out of new solar customers. in Scotland it costs £600 for a grid connection even if they have to do "nothing" at all. ELNW charge nothing for the same service so they have come up with an alternative way of extracting money out of you. when you apply for a grid connection they do some calcs and if you are wanting a G59 connection they come up with the excuse that this connection will put the line voltage above spec, so they say they will have to wind down the transformer at a cost to you of £1200 the line spec voltage spec is 208v to 253V, 253V is the absolute max allowed line voltage. also if your voltage is up at this level all of your appliances motors etc use more electricity to do the same job. that is why these input voltage limiters are worth considering if you are a heavy consumer with high input voltage.they limit the input voltage to 220V
 

Exfarmer

Member
Location
Bury St Edmunds
Most motors do not use more power at high voltages as the amperage consumption drops at the same time.
I have yet to speak to anyone who has seen any benefits from voltage regulation, in terms of power consumption.
 

Clive

Staff Member
Arable Farmer
Location
Lichfield
Sounds like battery tech is long overdue to me - that will surely be a game chager for domestic ? We would use most of our power at night which doesn't really work with solar I guess !!

I was in holiday last week with a friend who is a lawyer for a very large global renewable co who was saying they are now building none sub dependant solar installations (industrial scale) as the panel cost had now got so low - this is what got me thinking it might be viable for my house
 

f0ster

Member
battery tech is still a long way off paying back, a kit giving you 4kwh of useable energy costs over £2k, plus installation and profit for the installer, this same energy will cost you 48p buying it of the grid, you get to use the battery energy on an evening every day so it mounts up, usually some times in daytime as well, but on a less than sunny day your system might use the energy in the day time and not have much left for the evening.
 

renewablejohn

Member
Location
lancs
Sounds like battery tech is long overdue to me - that will surely be a game chager for domestic ? We would use most of our power at night which doesn't really work with solar I guess !!

I was in holiday last week with a friend who is a lawyer for a very large global renewable co who was saying they are now building none sub dependant solar installations (industrial scale) as the panel cost had now got so low - this is what got me thinking it might be viable for my house

Get the technology right and you can have 24/7 solar but it uses high temperature solar thermal rather than solar PV. Still not convinced batteries are a viable alternative unless used as a vehicle as well.
 

Exfarmer

Member
Location
Bury St Edmunds
I believe the battery issue is a bit of a red herring. It is not just the cost but also the size needed to store any real amount of power. On sunny days in mid summer, my 8 kw set up can produce 50 +KWH but at most I will probably use 15-20 and that includes heating a pool. For days on end we are just using a few Kwh to run lights etc in the evening.
Then you will have 3 months in winter when we can use it as fast as we generate.
Battery storage is far more use in countries nearer the equator where you are active long after the sun has gone down but you have good generation all year round.
 

Exfarmer

Member
Location
Bury St Edmunds
This makes sense to me, I hate sub dependant stuff so will wait a bit longer until it stacks up domestically without I think
In theory, and I suspect reality, it should be possible to buy panels and inverters, much cheaper , that are not licensed for FIT use. Or alternatively buy second hand panels , which have little or no value.
This licensing requirement has always put a large premium on prices and was a typical EU reg gold plated by DECC to ensure everyone gets a crack of the whip.
You will need local Area Network Provider, approval of course as it will still be feeding into the main
 
Currently renovating the farmhouse, it's not by the farm yard so this would be purely domestic use

about 100m from the farmhouse is a new 4000 sqft barn - one side of the roof faces directly south but is far enough away and out of sight to not be an aesthetic carbunkle !

what would the cost of a solar installation be that could provide the needs of the house ? (it's a big house circa 10k sqft) is there any financial case for building more capacity than the house will use for profit ?

is this all dependant upon feed in tariffs still or does it stand on its own 2 feet now financially ?

Should be under £1000/kw installed now for what your looking at. I know somebody who looked at putting them on a barn conversion very recently and instead opted for ground source heat pump instead for the heating. I've seen that in action and it's very efficient for that side of things. He's left his elec requirement to come off the grid due to his main use being at night. This was for around 8k sq ft property.
 

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