Hi Everyone,
we moved into a new house and we’re planning our first solar system and we would be very grateful if you could help us out with any advice.
We have an East - West facing roof with some shade on one side. (The building next to us casts a triangular shaped shade on the center of our East side roof, that’s disappearing by 11:30-is.)
We would like to have a system that supports a 15kW/day usage in case of an outage on the grid on a winter day. (Our summer, normal usage is around 8-9kW currently, but we just moved in, we don’t have enough data points yet, we’ve been living on ready meals for the last 2 weeks, didn’t get new electrics etc.)
We’re in the
UK (Northamptonshire), where we get 8-9hrs of daylight during winter.
Peak insolation hours are: January: 0.6 / February: 1.17 / March: 2.07 / April: 3.15 / May: 3.83 / June: 4.31 / July: 4.28 / August: 3.62 / September: 2.53 / October: 1.51 / November: 0.83 /December: 0.49
We had 3 surveys so far and talked to several companies, but we’re getting conflicting information. We would like to have an oversized system and can easily accommodate 20 panels (8kW system) on our roof (16 on the West side, no shade, and 8 on the East side, probably also safe from shade, but there might be some shady corners - we have no way to know yet; we just moved in and have trouble seeing the roof and calculating the shade-free area.) Therefore, the 8 panels on the shady side will have either optimisers or microinverters.
So far we got 3 suitable offers:
Option 1: this is the most expensive. We understand this would allow us to use “island mode”, which for us, ignorant people means pretty much being independent from the grid and provide enough electricity for our needs, winter/summer and turn the incoming grid power off, if we llike.
We were told we cannot NOT feed electricity back to the grid, because once we’re not using more, and our batteries are topped up, the produced energy NEEDS to go to somewhere, and that’s the grid (we can either sell it or give it away for free, but it needs to go there.) Is this correct?
This system would have:
- 20 Longi Hi-MO 5m monocrystalline panels
- 8 optimisers
- 2x3.6kW GivEnergy hybrid inverter
- 2x9.5Wh GivEnergy batteries. (If we want to reduce costs, we can have 2x5.2kWh batteries instead.)
We’ll need power diverter and PV protect but no voltage optimiser. We were told this is a big work, the electrician would change our system so much they will issue a new NICEIC certificate. (Bear in mind it’s a new build.) We understand they will rewire all the electrics with a secondary feed to the solar system.
We would have a changeover switch - in case of blackout, we would be able to manually switch to full solar mode/separate ourselves from the incoming grid electricity. Our electrics will still shut own, but we can just switch to use our batteries instead of the grid.
Option 2: this would need us to choose a couple of slots from the fusebox to be connected to our solar system. We won’t be able to operate all our equipment from solar in case of a blackout, just the ones that are wired to our solar system (e.g. boiler, fridge, micro, wifi, computers or whatever we pick).
This would have:
- 16 Longi Hi-MO 5m monocrystalline panels
- 8 optimisers
- one 5KW GivEnergy hybrid inverter
- one GivEnergy 9.5kWh battery
Option 3:
this company said they don’t even deal with connecting us to the grid - what we want is easy and possible without feeding electricity back to the grid and it’s possible. (Is this true?) No visit from the grid people is needed, no permission, no power diverter, no PV protect is needed.
They gave us a quote for:
- 20 Longi Hi-MO 5m monocrystalline panels
- 8 optimisers
- 3 GroWatt 6.5kWh batteries
Which option do you think is best from the above? Option 1 is almost double the price of option 3.
Meanwhile, another company keeps telling us, we’re really oversizing our system, it doesn’t make any sense; we should get 10-12 panels max.
What do you guys think of the above options?
Since we’re in the UK, one of our worries are that during winter we won’t produce enough V to startup the inverter in the morning, unless it’s very sunny, so we might be spending a lot of money on something that might not work. (Stupid side question: isn’t it possible to start up the inverter from batteries?)
Our main objective is not to save money, but to be able to use our essential equipment if there’s an outage, especially during the winter (last year there were outages that lasted for 2-3 weeks in some areas). (Combi boiler with a 40W pump, 900W micro, 3 computers, maybe a little electric heater etc.)
If we could avoid feeding electricity back to the grid, we would like that - it would indeed save us some money on equipment and hassle, getting permissions, visit from the grid people etc. We got conflicting info about it, so we don’t even know if this is possible or not.
We would be very grateful for any advice and confirmation about our inverters (needing 120 V or 150V startup voltage) to start working early on a winter day… I couldn’t calculate for how long it would take for them to start up in a cloudy, winter day.
Again, we don’t care too much about the return of our investment - we want backup power supply in case there are weeks of outage or issues with electricity (and potentially gas) supply.
Thank you!
PS: You guys rock - we read through so much of your advice on this forum and learnt so much from you already.