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fuuoldself

I have been doing some research and getting my first few quotes in for a modest sized solar PV and battery setup.  How do people feel about this offer

2.6kW PV panels
5kW battery
8kW inverter

£10k fully installed with all the DNO stuff, etc.

Small consumption <2kWh per year.

I do not 100% understand the decision on the inverter size, there's a suggestion it helps with hybrid battery/grid operation, plus any future storage upgrades or additional of electric vehicles etc.

Gut feel is it is a little on the high end but not unreasonable. 

Hexane

Why only 2.6kW of panels? Are you extremely short of roof space or something?

fuuoldself

Hexane said:

Why only 2.6kW of panels? Are you extremely short of roof space or something?

Afraid so. Fairly small mid terrace

Hexane

make sure to be getting at least 400W panels

Screwdriva

I would suggest maxing your panel output. Sharp offer upto 540 Watt per panel - feedback is excellent! 

https://www.sharp.co.uk/solar-energy/find-a-solar-panel

I would also suggest going with a much smaller inverter to maximize efficiency + skip the battery for now. Unless you're a heavy nighttime user, you can sell excess energy via the highly lucrative Octopus Agile Outgoing and save that upfront cost.

Assuming the above, your revised quote should be < £7K

fuuoldself

Interesting links, thanks.  Going to see what other quotes suggest.  This latest one are 365W panels.  With such a small roof area I guess every W per square meter will count.

Re; to-battery or not to-battery, as this is a first-time solar install I haven't got my head around how and when i want to consume the energy i generate.  My simple reasoning was battery = more flexibility (at a higher initial cost)

QrizB

fuuoldself said:

Interesting links, thanks.  Going to see what other quotes suggest.  This latest one are 365W panels.  With such a small roof area I guess every W per square meter will count.

Panel efficiency doesn't vary very much. Higher-wattage panels are usually proportionately larger, ie. a 500W panel is twice the size of a 250W one.

Where changing panel size can help is where you need to optimise the coverage on your roof. For example you could imagine a situation where you could fit two 300 watt panels, but only one 400 watt one.

fuuoldself

QrizB said:

fuuoldself said:

Interesting links, thanks.  Going to see what other quotes suggest.  This latest one are 365W panels.  With such a small roof area I guess every W per square meter will count.

Panel efficiency doesn't vary very much. Higher-wattage panels are usually proportionately larger, ie. a 500W panel is twice the size of a 250W one.

Where changing panel size can help is where you need to optimise the coverage on your roof. For example you could imagine a situation where you could fit two 300 watt panels, but only one 400 watt one.

Thanks, good point.

I think that's what's happening here with the 365w panels. I wouldn't be able to squeeze as many 400w panels into the same space as seven of the smaller ones.

Screwdriva

fuuoldself said:

Thanks, good point.

I think that's what's happening here with the 365w panels. I wouldn't be able to squeeze as many 400w panels into the same space as seven of the smaller ones.

It isn't very difficult to measure this - panel dimensions are provided and your roof measurements should be relatively easy to determine. It is almost a certainty that you will be able to fit larger panels than 365W. Given your limitations, every Watt matters.

fuuoldself said:

Re; to-battery or not to-battery, as this is a first-time solar install I haven't got my head around how and when i want to consume the energy i generate.  My simple reasoning was battery = more flexibility (at a higher initial cost)

There is another thread trying to get to the bottom of this very question. I recommend modeling out your usage pattern, expected generation and sale of energy. You may find that it makes little sense to pay such a large amount to store energy when you can sell it for nearly the same price you can purchase it for (making the grid your "battery")

fuuoldself

Screwdriva said:

There is another thread trying to get to the bottom of this very question. I recommend modeling out your usage pattern, expected generation and sale of energy. You may find that it makes little sense to pay such a large amount to store energy when you can sell it for nearly the same price you can purchase it for (making the grid your "battery")

I can scrape my 30 min usage data easily enough from a site like https://data.n3rgy.com and average out the watt hours by day of the week and interval to get a set data for my average usage broken down by day.

Are there any recommended sources for modelling expected generation by hour?  I found a calculator on https://pvwatts.nrel.gov and configured it with my planned installation.  Although it's a US body, the weather data used was UK based and within 100km of my actual location.  It offers a few measures, including DC Array Output (W) and AC System Output (W). 

Unsure of which figures to use, I took AC System Output (W) and averaged the values in the same method as for the consumption.

My regular weekday usage sits between 100w and 200w in the working day with the expected morning coffee and mealtimes spikes.  

I was surprised by the pvwatts data suggesting my 2.6k system will be able to deliver peak midday averages of 800 Wh?! Seems a bit high to me.  Is there a better source for expected generation modelling? Or would my system really be able to generate this much?

(i am doing annual averages at first.  I will breakdown by month once i can trust the data source)

DougMLancs

PVGIS is a really useful tool for modelling generation https://re.jrc.ec.europa.eu/pvg_tools/en/