Probably find the 3.6kw inverter won't allow battery draw at the full 3.6 and it'll be limited. know my 5kw is only limited to 2.6kw from the batteries unfortunately.
Solar panels and battery - any real world reccomendations?
- Thread starter GinG
- Start date
Soldato
The batteries themselves have limitations as well. The smaller ones have less capacity to charge/deliver
Yes, my Huawei 10 kWh battery is two 5 kWh modules, so can do twice the output of the single module. Peak output is 7kW vs 3.5 kW of the single 5 kWh battery.
I’m trying to understand this post.
I get the PV to house is limited by the inverter capacity. What about the battery to house, or combined PV & battery to house - isn’t that too?
I guess the question is : once the PV generated or Grid charge power is in the battery, does it need to go through the inverter again for use in the house?
My battery is DC, so it must go through the inverter to house, which surely means the battery discharge to house is limited by the inverter dischsrge capacity?
This is the spec sheet for Huawei inverters. The battery input discharge on my 5kW model is more than the 3kW model.
Last edited:
Soldato
Thank you all for your replies.
Heading out to do a little digging now before ordering.
Heading out to do a little digging now before ordering.
Associate
Yes SDK, the inverter dictates the power supplied to the house. PV and battery power is DC, both need to go through the inverter to convert to AC as used by the house, so if the inverter is 3kW, that the max you'll get from either battery/PV/both. If its 5kW as you circled above, you'll get 5kW from the inverter max regardless of whatever batteries/solar PV is connected.
Which is what I posted above
I suspect @Journey is referring to a Tesla Powerwall battery, which is AC, with an integrated inverter/charger?
I suspect @Journey is referring to a Tesla Powerwall battery, which is AC, with an integrated inverter/charger?
Soldato
With a hybrid system the charge controller shunts DC directly from the solar into the battery pack, and then when you want to the battery power is then taken from the pack and pushed through the inverter into AC for your house. Some systems allow various battery sizes and inverter sizes to be combined, so you can be limited by either the inverter or the continuous output of the battery, which ever is lower. So if you only had one of the LUNA2000-5-SO 5kWh battery packs attached, the maximum output is 2.5kW, if you have the 10kWh model that is doubled to 5kW, and the 15kWh remains at 5kW also.
Some PV installers don't bother to mention this when you are having a system installed, so you could end up with a real imbalance when you require more power, and need to draw from the grid more often to achieve this, thus extending your payback time and increasing the energy bill. It could be something a simple as boiling a kettle, or an air-fryer at the same time as wanting to have the gaming PC on full tilt, and a big TV.
Soldato
Is there any realistic prospect of a relatively small solar & battery install paying off within 5 years? Starting to consider putting a pin in the plan to move house before then due to all the rising costs - although it's going to end up a bit cramped, it will probably make more sense to build more equity in the house to be able to buy something "better" when it comes to it.
The house next door (basically a mirror of ours) has 6 panels on the roof (South-East facing, no shade), which a quick google suggests would be 3kW? I reckon there's potentially space for 2 more, so possibly 4kW? Including a say 5kWh battery I guess we're looking at ~£8k installed, so would have to save ~£135/month - I need to speak to them to find out how much they're getting from it, can't be too bad as they've just bought an inflatable hot-tub which apparently runs exclusively from solar!
Current electricity bill is ~£125/month (fixed at 35.05p/kW), but looking at potential increases looks more like £180+ in 12 months time.
Daily usage is ~11-12kW and we have Octopus Go so could top up for 4hrs overnight at 7.5p/kW.
Any ballpark figures on what this could add to house value - I suppose the battery could be taken to the new house if/when we move (assuming the buyers didn't want it) in which case maybe worth going for a larger one to make the most of the cheap overnight power during winter?
The house next door (basically a mirror of ours) has 6 panels on the roof (South-East facing, no shade), which a quick google suggests would be 3kW? I reckon there's potentially space for 2 more, so possibly 4kW? Including a say 5kWh battery I guess we're looking at ~£8k installed, so would have to save ~£135/month - I need to speak to them to find out how much they're getting from it, can't be too bad as they've just bought an inflatable hot-tub which apparently runs exclusively from solar!
Current electricity bill is ~£125/month (fixed at 35.05p/kW), but looking at potential increases looks more like £180+ in 12 months time.
Daily usage is ~11-12kW and we have Octopus Go so could top up for 4hrs overnight at 7.5p/kW.
Any ballpark figures on what this could add to house value - I suppose the battery could be taken to the new house if/when we move (assuming the buyers didn't want it) in which case maybe worth going for a larger one to make the most of the cheap overnight power during winter?
Soldato
Nope I've clarified above.
Soldato
If you only think paying itself off with be of any value, rather than adding value to the house. I suppose it depends on the property price, and the upfront install costs though how much that matters. Ask yourself this, when you move if the next house doesn't have solar and energy prices are high will that put you off? If it had solar would that encourage you to buy it?
For the most part a solar install is almost a rounding error in total cost of the lifetime of the mortgage, as it is an asset to reducing costs, not increasing them - do you think people would be less likely or more likely to buy your house with solar installed, and you can show it's total value in energy generated and money saved over those 5 years? Even if you only save £3k in 5 years, do you think and £8k system will add £5k value, or make the house more appealing?
With that sort of usage, I'd be looking to get as many panels as you can afford as they aren't where the cost is, the cost is in the labour, scaffold, and certification etc. Doubling the number of panels might only cost and extra £1k, but could make your power usage from the grid much lower overall, so that £1k will be paid back fast.
Soldato
8 x 385w JA Solar panels
solis 5kw hybrid inverter
all electric cabling, fiiting and scaffold, mcs certs, seg certs etc etc
£5995
can add a battery at a later date of want too
solis 5kw hybrid inverter
all electric cabling, fiiting and scaffold, mcs certs, seg certs etc etc
£5995
can add a battery at a later date of want too
So, if you have a 3.6kw inverter and your battery can output 5kw, are you limited to the inverter output?
Soldato
Thanks both - I think the battery would be where a lot of the savings come from due to being able to charge up overnight? (especially relevant during winter!), but obviously doubles the costs. We're restricted on the number of panels due to available roof space (neighbours house with panels already, ours is the other half):
So potentially could fit one more panel on the top row, or a couple more if they were rotated 90 degrees (if that's even possible?), but that would be it
So potentially could fit one more panel on the top row, or a couple more if they were rotated 90 degrees (if that's even possible?), but that would be it
Soldato
Yes, because the inverters maximum AC output would be rated at 3.6kW, be that supplied by DC from PV or a battery.
Soldato
If you have AC coupled batteries, each battery will have its own inverter, so you would would have the sum of each battery and the PV inverter.
If the batteries are DC coupled to the PV inverter then it will just be what that single inverter could supply, unless the batteries have a lower limit for some reason, for example the maximum current they can supply.
If the batteries are DC coupled to the PV inverter then it will just be what that single inverter could supply, unless the batteries have a lower limit for some reason, for example the maximum current they can supply.
Soldato
You can fit panels in either portrait or landscape, so you can fit quite a few on there by the look of things. It is also potentially worth also doing the rear regardless of facing, if you can't get many panels up there as it will make a good difference still in the spring and summer. Is the roof angle quite shallow, can't really tell from the photo being top down.
As I mentioned to someone else, look at the cost the battery is adding, then ask them to take it off but leave the hybrid inverter if having one and see where that puts the costs for the pack, and the install, you might be able to save quite a bit having it done separately. But there are sums to do!
Associate
Interesting what you say about battery output being limited. When I look at the specs for the PureDrive battery the only ones that mention output are:
Discharge cutoff voltage: 45v
Continuous discharge current: 100A
Max discharge current: 350A (3 sec)
From this, how do you work out its maximum output?
Back of a fag packet 48v x 100a = max 4.8kw draw from the battery. Subject to the limitations of the hybrid inverter as mentioned. For reference my Luxpower/Pylontech combo is 66amp max battery draw.
A small draw from the grid because the oven is cycling on at the same time as the dishwasher will be pennies in the scheme of things, so I wouldn't worry much about this.
Soldato
Thanks again for the useful info, from eyeballing I'd say it looks like ~45 degrees pitch, might be time to speak to the neighbours about their figures and look at getting some quotes.