I’m embarking on a home retrofit and getting quotes for solar systems with batteries.
I’ve got quotes from 3 different companies, all saying different things. My house is east/ west facing with a pitched roof and 3 chimneys.
My electric usage is currently around 2900kw/year. 2 adults 2 kids. Having MHVR system, not ashp. Looking to future proof for elec car .
Ive had advice for between 10-17 panels. 1-2 batteries between 5-10 kw.
Can anyone advise on what I would ideally need in terms of a system? The picture shows my house, this is the south facing wall. Many thanks in advance
With respect to PV you are lucky that you have the south wall. Your chimneys are to the north and will cast negligible shadow.
The gable end to the west severely limits your westerly potential.
You can’t always go by panel numbers as the dimensions vary. Smaller panels fit near odd angles more easily than larger ones, so as well as needing more panels for a given area you might manage a larger area.
Potentially you might fit 10 panels on the south facing roof, so anything above 10 is definitely for the front and back. You get maximum generation per panel facing south, but at midday. Therefore if you go for a south only solution and the house is not occupied during the day you will really want your battery(ies). East facing panels give you most morning generation and in summer will provide for heating breakfast and maybe other tasks. Similarly one or two west facing panels will help boost your afternoon and evening production.
The figures for kW should be taken as rough guidance and with a pinch of salt. The quoted figures should be in kWp. That is your potential if all panels are simultaneously at the optimum angle to the sun. Clearly if you use more than one roof surface that cannot be true. Your inverter should be sized accordingly.
Regarding battery size, your minimum size should cover your base load for a winter day. Base load is what your household uses when nothing in particular is running. It will cover fridges, ventilation, hubs and maybe one or two lights. If you had a heat pump you could include that.
Anything above a day’s use is normally a waste unless you are plagued by power cuts and get a system that can run during a power cut. On the subject of power cuts, your PV will cut out if you have one unless you get a suitable battery.
For comparison, my electric usage is about 50% more than yours, with an extra child, hot water by immersion, MVHR and an EV. I have a 3.55kWp PV system with a Powerwall. I have similar orientation as you but I would guess further south (just north of London).
The following might be of interest:
Thanks for this Tim , much appreciated.
I seem to be missing something here. Doesn’t your original post @Luciya_Whyte imply that the gable wall facing the camera is the south-facing one? But if I understand you correctly @Tim_Gilbert you are taking that gable end wall facing the camera to be a west facing wall. Or am I hopelessly confused?
Looking at the photo, my understanding is that the “gable end” is actually a hip end. Therefore it can gave the majority of panels facing south, there is room for a lot of east facing panels (right of photo) and a few west facing.
To clarify perhaps the OP could annotate the photo.
Edit: Oops. My mistake. I’m looking at next door. I’ll re-answer after Father’s Day.
Sorry @Luciya_Whyte, I am now making suggestions relating to this house.
First a little info on panels and shading. Panels are wired to inverters in series from where the DC current generated is converted to domestic AC. Generally speaking the panels on a string can only produce useful power at the rate of the lowest producer. This means that if one panel in a string is shaded is reduces production from the rest of the string. In this scenario even slight shading can have a dramatic effect on overall production. The shading effect can be reduced by having inverters that accept multiple strings and arranging panels on strings dependent on how productive they will be. This needs an expert installer with a good understanding of the process. Alternatively panels can have microinverters. These work out more expensive and many installers don’t use them. The microinverters go up on the roof, under the panels. There would be one or two panels attached to each inverter. Power is then sent to the house as AC. Because only one panel is on each inverter the chain reaction of shading doesn’t occur.
Do your retrofit plans include removing any chimneys? The one in/on your south wall is sabotaging the prospects of any worthwhile south facing panels. In any event any roof work needs doing before the panels go up.
The south end of your front/west roof will be shaded a bit by the protruding roof. For a system on a tight budget needing a good ROI that means the north end will be the best investment. Any panels subject to periodic shading need to be on a different string into the inverter or on microinverters.
Your back/east roof, conversely, has periodic shading at the north end due to the chimney in that roof. The best ROI will be from panels on the south end. Again the rest of the roof could be panelled but the panels at the shaded end need to be on a separate string or microinverters.
Edit: ROI = Return On Investment
Can anyone recommend a good PV installer in the Stockport / S Manchester area