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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorjamesingram
    • CommentTimeOct 30th 2018 edited
    V eco run Pvgis for your location that give you pretty accurate monthly generation figures.

    Without Fits it's about 1000kWh per kW installed per year south England ( a bit less actually)
    Materials are around 50p/W
    That £150 per year if you use it all at standard purchase rate of 15pkW

    Anyone that can use all power generated
    £4k for 4kW system (£2k to get it installed)
    £600 electricity generated per year.
    15p kWh
    After 7 ish years everything it generates is free .
    First 7 years electric at standard rate so no additional cost
    DIY make that 3.5 years
    System life 25 years minimum
    • CommentTimeOct 30th 2018
    Colin, can you show any recent cases where councils have misinterpreted the law as they did soon after it was changed in the example you gave? I would hope that by now, even the most recalcitrant councils have understood. If in doubt, I would start by applying for a Certificate of Lawful Development rather than Planning Permission.
    • CommentAuthorCWatters
    • CommentTimeOct 30th 2018
    Think you might be right. Have found references to PP only being needed in a conservation area if the panels are wall mounted. Guess I'm out of date.

    Gives me 4300kWh per annum using the default settings and changing the azimuth to 15deg (based on a 4kW system)

    3.3kW per day in December and 19kW per day in June

    I guess I would need to see how much in reality I'd actually consume in a day when the sun is out? At best it would be the fridge/freezer, washing machine, dishwasher and top up the immersion. Best way to calculate these?

    I'm guessing the washing machine wouldn't run on 100% solar or would it? Not sure if it's a combination of solar and mains?
    • CommentAuthorbhommels
    • CommentTimeOct 31st 2018
    It really depends on what you want. The point I was trying to make earlier is that if you are installing without FiT and you want the highest returns, the array should be sized such that you can consume (almost) all electricity produced.

    If you are prepared to accept longer payback time, a bigger, more costly array will give you more power to make use of, however you should put systems in place to monitor & use the excess power.

    Note that most high power household appliances are basically water heaters: washing machine, dishwasher, kettle (electric shower). Running (some of) these off the (solar powered) hot water saves energy even when the PV is not providing sufficient power at that moment.
    Are the FIT's being withdrawn completely or just for new sign ups?

    Which kit on ebay in particular do you recommend James?

    If I could get an electrician to fit it, I guess I'd need to allow for scaffold and how many days labour do you think?
    • CommentAuthorjamesingram
    • CommentTimeNov 3rd 2018 edited
    FITs will be withdraw 1/4/2019
    This looks good, REC are a quality brand from Norway,
    caution this is just what popped up on a quick search. i've no direct experience of the seller, also just noticed , doesnt include mounting kit (£200ish)

    4kW standard house, easier roof layout, if you know what your doing 2-3 men on roof 1 on electrics for a day.
    Go for 2days x 2 men on roof and 2days x 1 inside to cover yourself , Its handy to have a 3rd man on the roof when fitting and carrying up the panels as theyre cumberson , which the guy inside can help with.
    • CommentAuthorjamesingram
    • CommentTimeNov 3rd 2018 edited
    get yourself some cheap plug in energy monitors such as
    combine them with a overral monitor and youre get a good sense of what each item uses and overal flow up and down

    energy companies used to give them away free , might be worth a try or get a smart meter fitted as this will come with a similar wireless consumption display I believe.

    Damons site is filled with useful info
    start here
    Posted By: VictorianecoAre the FIT's being withdrawn completely or just for new sign ups?

    Existing contracts should run for their specified duration.

    The opportunity to signup for new contracts will cease.
    So if one was to sign up now how long is the current contract for FIT?

    Can't seem to find anything..

    Found that so it seems one would get FIT for 20 years still!

    Looks decent to me!?
    Doing the maths and it still doesn't seem to add up to me. I'm not against the green element but somehow I think I'd be better off investing in a stocks and shares isa.

    I don't have a driveway so charging an EV in the future would be ruled out. Battery storage is not cost effective. The FIT based on what I could in theory get is low.

    Still not convinced at todays prices before even paying for an MCS fitter
    • CommentAuthorjamesingram
    • CommentTimeNov 4th 2018 edited
    V-eco depends on what you want , FITs will get you your install money back plus a return of sorts,
    in the future the saving will only get better. with an ASHP you get the opportunity to use all your generation at the time its sunny and ASHP is on.
    at 4300kWh generation per years you'll currently get
    Gen 3.86p x 4300 =166
    expo 5.24p x 2150= 112
    total £278 pa index linked 20 x 278 = £5573 over 20 years
    this doesnt include electricity saved
    low estimate 50% (could be more if you set things up right) 2150kWh pa at 15p= £322 x 20 = £6450 over term
    £4-5k to get an MCS install

    £12,023 over 20 years
    £5,000 capital so £7023 profit with return of capital = approx 4.4% interest rate ignoring energy price inflation
    Posted By: bhommelsThe point I was trying to make earlier is that if you are installing without FiT and you want the highest returns, the array should be sized such that you can consume (almost) all electricity produced.

    How would you make this calculation with such a variable power source? Size the array so that it produces 100% of your requirement in winter, summer, spring, autumn, sunny days, rainy days, overcast days?

    Do you size it with your current consumption in mind, or factor in the fact that you may buy an electric vehicle in future, or we may have to all install air conditioning systems due to climate change. Plus battery technology and costs are improving all the time, which will allow us to use more of our generation.

    A large portion of the cost of solar is the installation, such as scaffolding and labour fitting the framing and panels, wiring up the array and connecting it to the house consumer unit. These costs are not proportional to the size of an array (for example, scaffolding is the same whether you fit 100w or 5kw of panels on the roof).

    I'd always advise people to install the largest array that they can afford and that their roof allows so that they are future proofed.
    • CommentAuthorbhommels
    • CommentTimeNov 5th 2018
    @Pile-o-Stone: all good questions. I did not say that the solar PV should cover all usage all of the time, as you say this would be impossible. What I wrote is that for highest returns you should aim to consume all energy produced.
    The OP aimed at a DIY install, so I assumed scaffolding, labour to be free. Then the panels start to dominate the cost, and a smaller array will provide better returns.
    If there is FiT on offer etc, I agree that the largest array you can accommodate is best.

    I reckon there's a maximum of £300 saving to be had

    I think I'll keep my cash in my stocks and share ISA and earn 10% per year. I'm happy to take my chances I think.

    My personal opinion is that costs will come down even further anyway so will all balance out
    • CommentTimeNov 5th 2018
    Posted By: VictorianecoI think I'll keep my cash in my stocks and share ISA and earn 10% per year.

    That's pretty optimistic. I hope you have good skills.
    You can't really outsmart the market so I invest in long term indexed tracker funds with accumulation rather than dividends.

    Long term investments, compound interest and so on..

    My wife also has a LISA which investing £4000 a year in gives her an automatic £1000 bonus. Ie 25%...

    So yeah 10% is easily achievable as an average on what I invest
    • CommentAuthorjamesingram
    • CommentTimeNov 6th 2018 edited
    v-eco what ratings is your ASHP and when is it on usually. Do you have a buffer tank ?
    do you know your annual.total electric use in kW and cost?
    Do you know the kW usage per year or monthly of the ASHP.
    It's an ecodan 8.5kw, it runs at 5pm and 5am to top up the hot water to 50c (210l tank). No buffer present

    Not sure on annual usage exactly but we pay £85 a month and always end up in credit. No gas at the property either.

    Heating is on 24/7 when required and flow temp is 30-40c depending on outside temperature.

    Never measured the electric use of the ASHP in all honesty.
    Phoned 5 local mcs solar pv installers this morning around 9am. Not one has returned my call all day
    First company to actually answer is ballpark £5500 but no RHI as no longer MCS registered.

    Who wants to fit some in South Wales for me then? 🤔
    • CommentAuthorjamesingram
    • CommentTimeNov 11th 2018 edited
    FITs you mean
    have a chat with wind and sun they may know of a decent local installer
    some guesses 365 x 0.19 = £69.35 standing charge
    annual bill 12 x £85 = £1020 approx £1000 say
    take off ST = £930
    average £0.16 per kW
    so 5812 kW used per year
    most will be for heating then HW
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