Spent the last week reading this whole thread
Hero! 103 pages / 7 days = 97 minutes per page. Comprehension should be good
Possibly looking at an air-rad heat pump in a year or two
Winter heating? You will get diddly-squat from PV in winter (Dec/Jan will be 10% of mid Summer peak). Oct-mid-Nov and Mid-Feb onwards you will get some - but weather has to co-operate by being sunny on cold [
central heating] days ...
didn’t seem all that knowledgeable about battery storage, how to design a system to best make use of energy plan time of use
I suggest you need useful logged data for consumption. You need to know hour-by-hour what you use in various scenarios:
(Hour-by-hour because you need to know what is during Off Peak (you can price that buying from Grid), whether likely to have some PV at that time, and for the rest "Price from grid")
Winter, artic outside, heating on full blast. Both "house occupied" and "away for weekend"
Normal average Summer day consumption. Maybe a party-day as well as an ordinary at home day - and a weekday / weekend day. Baking / Washing / tumble drying days (if you have those high-consumption days) vs. normal days
Smart Meter (got one of those?) might give you that data, or a plug in gadget such as Owl
Then, if you are up for it, you need to crunch those numbers. I think the calcs you need are for:
Winter days - assuming you will charge the battery 100% on Off Peak (in Spring/Autumn that will be partially-charged on some/majority of nights - depending on prediction of tomorrow's sun [Tesla and Givenergy will do that, or you can roll-your-own using e.g. Solcast])
What is the consumption from end-of-off-peak to start-of-off-peak following night? Your ideal would be a battery that can cover that. I guess 80:20 would do - so what size battery would cover 80% of the days usage.
However, you probably don't actually want to try to achieve that in Dec/Jan. By mid Feb you will get some useful sun PV (when it isn't raining - if it rains then same sum-game as Dec/Jan). Use figures for likely Monthly generation which you can put in the mix. My battery does about 1/3rd of a winters daily Peak tariff, but by mid Feb I have days where I use zero Peak tariff, and only charge battery to 50% on Off Peak - enough to run until Sun Up, and then Sun will charge to 100%-ish, and then that will run down from 14:00 - 15:00 (
Feb PV-SunDown) onwards ... up until Off Peak starts.
In Summer the tables turn. You want the battery to go from "PV SunDown" (
the moment at which the PV is generating less than the house is using) until PV-SunUp. If you have East and West arrays that will probably be 2 hours better than a South-only array. Of course that includes the night time, which will be your lowest consumption, which helps eek the battery out. My battery will last me a bit over 12 hours (over night) at Summer Consumption, at which time my PV-SunDown to SunUp is about 7PM to 7AM.
On top of that no point installing panels if you cannot use their output - bigger battery, or a car (parked at home during nice sunny summer days, Natch!), or a summer usage - Air Con, Hot Tub, Immersions etc.
I am a relatively high user
Yeah, me too
27x 425 Panels; 5 South, 8 North, 14 East
Not sure the North are going to contribute enough (on top of the others) to make them worthwhile.
Multiple elevations may require multiple inverters, or some other fancy "balancing" stuff. (Not something I know about, but might mean that North benefit is offset by having to buy "more stuff" like inverters, wiring, scaffolding, etc.)
as well as being an authorised Tesla Powerwall installer
Ask them what their lead-time is. If it is 12 months (might well be ...) then you might want something else
f I’m having to faff with 3 other interfaces all the time then that’s not as good
If you are going to plug-and-forget that won't matter, You could install e.g. a Zappi charger and let it just divert excess PV to Car (if it is at home and plugged in) and use Eddie (IIRC??) to divert excess power to Immersion and so on.
If you want to tinker then I think it it definitely helps. I can go into Tesla APP, see that the battery is almost full, PV has several hours peak to go, and I can start one/both cars charging (and choose low AMPs if I only want to divert a bit). I don't think I'd do that as often if I had to go in and out of several APPs. All that can be "automated" with Tesla API. Again, harder if there are several different APIs to make connections to - and X-times more hassle whenever anything changes in any/one of them.
Useage; 19,000 total pa (probably 30 kW a day in summer? 50 in winter? Excluding the car)
I don't think that figure is useful. You need a) household consumption in various scenarios (as described above) and then match that with likely PV production (month by month). I suggest you have a go with
PVWatts - that will let you figure out (for your exact location) what roof area you have (for each elevation) and [at that Lat/Long] what your likely generation will be month-by-month
Make separate calcs, for each of your orientations. Then copy/paste the month-by-month production figures to a spreadsheet - and then see when producing more than house will use, and when not enough. That can influence battery size (or whether you need car to be at home any day in Summer when sun is shining! or also buy an Air Con system for the house! and also clarify that you aren't going to get any benefit for winter heating in Dec / Jan at least)
The hot water cylinder water that’s pumped around in a loop and heated almost 24/7.
I have a loop system like that. We have a pump (
special hot water pump - I think that is referred to as "bronze") which comes on to pump the ciruit, on a 5 minute timer and overridden if thermostat sees that the return temperature is "hot"). We have bedside / bathroom switches (on home automation system) to "trigger" that. The plumbing is configured so that there is a non-return valve when pump is running, and when not the hot water can flow both ways round the loop - which provides benefit of more hot water "flow" than only a single circuit.
Before we put the pump in the water cylinder was cold within about 4 hours.
We also have towel radiators
on the hot water circuit (special towel rails, stainless maybe?, sorry about that ...). Run the pump (and/or run a bath/shower) and the flow of hot water heats the towel rail, which coincides with use of course. Or just turn the pump on if you want the towels heated at any other time.
I’m thinking I need the max panel version due to non optimal roof
If you are doing it you want to put up as many panels as you will ever need - there is a fixed cost for scaffolding and "getting installer on site", and quite possibly "one inverter", so incremental cost of a few more panels is small.
Any car charging from excess in the summer will be a bonus
If you are sizing to have a reasonably decent amount in Spring / Autumn you will definitely have excess in Summer.
Adding Air Con, in Summer, would use up some excess ... even a plug in one with a snorkel-pipe out-the-window would do. Or some other heavy summer time usage.