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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorowlman
    • CommentTimeJun 16th 2023
    Has anyone gone down this route, and if so whose battery system did you use; -- is it good or bad; are both battery and the system working well? My neighbour swears he's saving money. I wonder about the ROI of such systems.
    • CommentAuthorDougmlancs
    • CommentTimeJun 16th 2023
    I’ve a 9.5 kW Givenergy battery with my 4.5kW PV system a couple of months ago and am very happy with it. The main reason we went for a battery is that we’re switching to an ASHP in a fortnight and it will be vital to making sure as much of our usage is off peak as possible. The ROI for us will be 5 years but our battery was a good deal compared to many prices I see quoted. We’ll find out if the battery is big enough to see us through on something like Octopus Cosy which has two 3hr off peak charge windows per day. Generally, with Octopus offering decent export rates, it’s those with very high usage like an ASHP, EV, long electric showers, crypto miners, etc that see the best ROI on a battery system. Another perk is you don’t have to obsess quite as much about timing appliances!
    • CommentAuthorrevor
    • CommentTimeJun 16th 2023
    We have a 10 Kw BMZ battery and Delios inverter and 6kw ground mounted panels. It is questionable whether it is cost effective there are so many variables to do with pricing of what you buy in and what you export. On balance we are pleased with it. This month we have filled the battery to 100% by midday or thereabouts and go on on a full sunny day to export 28 to 29kwh. Our self sufficiency this month has been 99% plus and May was 98%. Our freezer is running a lot and overnight the battery runs it and loads left over in the morning for breakfast. It avoids using electricity from the grid if you plan it right. For instance we will shower in afternoon as the solar and battery can support it. Battery will deliver 5kw peak so if we used shower in evening it would take 5 from the battery and say 2 or 3 from the grid. We time appliances to suit i.e. washing machine dishwasher etc. Things like induction hobs that can draw up to 7kw on start up are managed by ramping up the power slowly otherwise grid kicks in if battery senses overload on it. At moment export payment been a lot lower that last year so was getting better return then. With the payment for export we increased our credit to the point we paid nothing for electricity and the surplus paid for the limited amount of propane gas used for heating. Could not have achieved that without the battery.
    You can get them to power the house during outage but we have not configured our system to do that yet.
    • CommentAuthorowlman
    • CommentTimeJun 16th 2023
    Thanks both;
    I'm toying with the idea of storage. I have 10kW of PV and as I slowly make my home all electric, consumption will only go up so on the surface it kind of makes sense.
    At present, the majority of my PV production goes back into the grid. In the evening when we cook etc I'm importing. As you say Douglas, timing ones life around PV production can become a chore, and the freedom sounds good, even out the supply and demand.
    For me, at the moment, the "wheel's still in spin" and I need to crunch the finance figures, but in my mind it looks good. I've also still to some more battery research as to which system would suit my needs.
    • CommentAuthorcjard
    • CommentTimeJun 17th 2023
    If you can get a symmetric tariff does the grid notionally become one big battery?
    • CommentTimeJun 17th 2023
    Posted By: cjardIf you can get a symmetric tariff does the grid notionally become one big battery?
    It might but AFAIK there's no such thing here. You get charged for consumption at retail rates and paid for export at wholesale rates, at best.
    Posted By: cjardIf you can get a symmetric tariff does the grid notionally become one big battery?

    No symmetric tariff here but we have annual reconciliation which means that whilst the import price (including grid charges) is retail and the export price is wholesale production price because the reconciliation is annual there is no point to getting a battery. The target for a PV installation is to end the year at zero i.e. import = export.

    Next year the plan is to go to monthly reconciliation for new customers and most PV installers are saying this will kill the market.

    IMO annual reconciliation makes sense because you can use the grid as a big battery and surely the environmental and financial cost of a domestic battery / kWh is more than wind or PV / kWh on the grid.
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