Solar panels and battery - any real world recommendations?

I'm looking at getting Solar + a battery next week. I don't think i can get much more than 3.6kw on the roof however i'm looking at a 10kwh battery.

The company that have specced it have only specced a 3.6kw hybrid inverter however i'm not 100% sure how this works. If for example the panels are maxed out and the battery is full & i jump in the shower at 9.5kw what happens?

Do I get 3.6kw from the panels & have to rely on grid for the remaining 5.9kw or can the battery help leaving the grid to only supply 2.3kw.

I'm going to want a bigger inverter aren't I?
 
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Is it elec only house or elec+gas
What is the heating type, what about levels of insulation etc

Just wondering if a bit spent on insulation, and maybe windows could be better invested.

Or maybe consider saying you will give them £50 a month towards utils Oct-Mar (which is the only time realistically people should have high bills no matter the heating source)
Costs you £300 a year which is going to be less than getting batteries installed and gives them a similar end result.
 
Iamzod said:
I'm looking at getting Solar + a battery next week. I don't think i can get much more than 3.6kw on the roof however i'm looking at a 10kwh battery.

The company that have specced it have only specced a 3.6kw inverter however i'm not 100% sure how this works. If for example the panels are maxed out and the battery is full & i jump in the shower at 9.5kw what happens?

Do I get 3.6kw from the panels & have to rely on grid for the remaining 5.9kw or can the battery help leaving the grid to only supply 2.3kw.

I'm going to want a bigger inverter aren't I?
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It varies on what an inverter can actually handle but its not going to be vastly above 3.6kw, maybe 4kw
But yes the grid will provide any draw above the inverters max. The inverter cant supply energy from both grid and battery at max level, a combination of both.
How long do you realistically spend in the shower as it may not be worth going larger inverter.
They don't cost a lot more for larger ones, but technically they are less efficient the lower the % they get from solar, and a 10kw inverter is a big one.

Also different batteries have different max discharges as well so you would need to have one specced for 10kw discharge if you wanted to do that as well.
 
Johnson9 said:
Don't really care about whole house backup - it's a house in Manchester, don't think there was a single power cut in the last 10 years.

It's a rental property and renters are complaining about high energy bills. I thought if I get them a good battery it will drastically lower their electricity bill. I have a Powerwall 3 at home and practically haven't payed day rate since it was installed.

As an alternative to a big battery I'm considering say 10 solar panels plus a 5kwh battery. But the problem is the roof is North/South facing and there are tall trees on the South side.

One thing I'm slightly worried is the renters may sigh up for a VPP and quickly wear down the battery.
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Not sure I’d be installing a battery system in a rental property, that’s a lot of risk on your part, it’s very easy to rip out and has a lot of value on the used market. It could also get damaged easily, don’t forget a battery is effectively a consumable, a long lasting consumable but still consumable.

What ever you install you’ll be on the hook for supporting and maintaining as it will effectively become part of the property.

Perhaps if you needed to make energy efficiency improvements a solar only system makes a lot more sense. Do north and south facing panels - north is very cost effective now. If you have shading issues, installers can do a micro inverter or optimiser system. You can also get grants as a landlord for EV chargers while you are there.

Otherwise I would look at the fabric of the building, windows, insulation etc.

Energy costs are high generally, they may just use a lot of energy.
 
Mercenary Keyboard Warrior said:
It varies on what an inverter can actually handle but its not going to be vastly above 3.6kw, maybe 4kw
But yes the grid will provide any draw above the inverters max. The inverter cant supply energy from both grid and battery at max level, a combination of both.
How long do you realistically spend in the shower as it may not be worth going larger inverter.
They don't cost a lot more for larger ones, but technically they are less efficient the lower the % they get from solar, and a 10kw inverter is a big one.

Also different batteries have different max discharges as well so you would need to have one specced for 10kw discharge if you wanted to do that as well.
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It's not just the shower. We've got an air source heat pump and some other high load stuff like a 1.8kw A/C unit, 3.5kw pool heater and soon will have an electric cooker.

I imagine cooking in winter when the heating is on will hammer 3.6kw and not leave any room to add more batteries in should i see fit.
 
Iamzod said:
I'm looking at getting Solar + a battery next week. I don't think i can get much more than 3.6kw on the roof however i'm looking at a 10kwh battery.

The company that have specced it have only specced a 3.6kw hybrid inverter however i'm not 100% sure how this works. If for example the panels are maxed out and the battery is full & i jump in the shower at 9.5kw what happens?

Do I get 3.6kw from the panels & have to rely on grid for the remaining 5.9kw or can the battery help leaving the grid to only supply 2.3kw.

I'm going to want a bigger inverter aren't I?
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Fit as many panels as will fit on the roof as possible on all aspects including north.

The cost difference between a 3.6kw and 5kw inverter is minimal so suggest going up to 5kw to enable better charge and discharge from the battery (assuming the battery also supports it).

Edit: just saw your post above, how much battery storage are you considering?
 
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b0rn2sk8 said:
Fit as many panels as will fit on the roof as possible on all aspects including north.

The cost difference between a 3.6kw and 5kw inverter is minimal so suggest going up to 5kw to enable better charge and discharge from the battery (assuming the battery also supports it).

Edit: just saw your post above, how much battery storage are you considering?
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Battery storage 10kw initially but they have said we can add more in as we need, so may well end up with 20kwh.

I'm planning to use one of the multi rate tariffs with Octopus, maybe even Agile so i want to not be using grid early evening.
 
Iamzod said:
Battery storage 10kw initially but they have said we can add more in as we need, so may well end up with 20kwh.

I'm planning to use one of the multi rate tariffs with Octopus, maybe even Agile so i want to not be using grid early evening.
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You won't want to be in agile with that use load IMO. You sound like a heavy user who would benefit from more battery and load up cheap overnight. 6.7p on Eon or Octopus go a bit higher will save you more than agile these days. I have a 9.5kw battery with no heat pump or electric shower or other stuff and that lasts me just about a day in winter.
 
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Iamzod said:
Battery storage 10kw initially but they have said we can add more in as we need, so may well end up with 20kwh.

I'm planning to use one of the multi rate tariffs with Octopus, maybe even Agile so i want to not be using grid early evening.
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Sizing batteries is the trickiest part as it’s a balance between cost, solar production and energy use.

Once you have ‘enough’ batteries, the RIO goes down as you add more where as with solar, the more you add the higher it gets.

You don’t need to aim for zero peak rate usage, that is the fallacy many people fall down. Don’t forget, tariffs like Octopus Cosy also exist where you can charge the battery 3 times a day at a higher rate (still half the peak rate) which will be cheaper than adding more battery storage to cover heat pump winter usage.

A key point is what does your daily energy consumption look like, how much of that can be done off peak?
 
b0rn2sk8 said:
Sizing batteries is the trickiest part as it’s a balance between cost, solar production and energy use.

Once you have ‘enough’ batteries, the RIO goes down as you add more where as with solar, the more you add the higher it gets.

You don’t need to aim for zero peak rate usage, that is the fallacy many people fall down. Don’t forget, tariffs like Octopus Cosy also exist where you can charge the battery 3 times a day at a higher rate (still half the peak rate) which will be cheaper than adding more battery storage to cover heat pump winter usage.

A key point is what does your daily energy consumption look like, how much of that can be done off peak?
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On a normal day we can move stuff around a bit like the tumble drier, dishwasher & washing machine with no real issue as I work from home, my big problem is showers as I like to have a shower at about 7am and then again at 5pm, particularly in summer. Maybe I ought to move to a mixer shower now I have the ASHP.

This is why I was favouring agile, we pay 24p per Kwh as it is and it looks like it mostly stays under that anyway and of course the battery will take half that load reducing it to an effective 12p anyway (with a 5Kwh inverter).

Our energy usage prior to heat pump fitting in 2024 was 6464kwh for the year so we only average 17.7kwh per day, but that's made up of really low days & then there will be some where we hammer it & go over 30kwh (Highest day i've seen was 38kwh)
 
Yeh you want to transition to mixer showers, not necessarily because of the energy use but they are utter **** compared to a mixer shower connected to an unvented cylinder which you’ll have with your heat pump.

Your usage is quite high so it probably comes down to 10kwh and making heavy use of octopus cosy from late autumn to early spring or 20kwh and sticking with Go for as long as you can, possible all winter.

I’m not sure which will come out better, I suspect they’ll not actually be much in it.

The other thing to consider is inverter size and cheap periods. You might not get 20kwh of batteries recharged in a 5 hour cheap window without a decent inverter. Batteries don’t charge linearly and slow down as they fill. The Cosy cheap periods are typically only 2-3 hours so you’ll want at least 5kw, ideally 6kw.
 
Hello!

I'm about to pull the trigger on a solar install. I've had 10 quotes (yes 10!).

My home setup is:

  • 12kw Vaillant Arotherm Air Source Heat Pump
  • No gas supply
  • Likely to use 10,000kwh per year (This is my first year with the ASHP so this is fag-packet maths based on converting previous gas consumption against my ASHP COP)
  • Peak daily consumption was in January (78kw)
  • Average consumption per day (kwh): Aug (10), Sep (20), Oct (28), Nov (39), Dec (39), Jan (47), Feb (42), Mar (26), Apr (20)
  • Likely to be able to fit 10 panels on the North facing roof, 10-12 panels on the south aspect
  • I have Home Assistant

This is the quote I'm likely to go for:
  • 20 panels (Trina Vertex)
  • 10.8kw total inverter capacity Solax inverter (a 7.5kw inverter and a 3kw inverter - not sure why there are 2 inverters)
  • 21.6kw Solax battery
  • Bird netting
  • No rewiring to cope with grid failure (waiting on the price for that to follow later tonight)
  • Local firm recommended by a neighbour, MCS registered
  • Visited for initial survey
  • Price - £15,100

Overpriced? Seem like a decent design given our usage? Anything I should be asking to change on the quote before pulling the trigger?
 
Marakith said:
Hello!

I'm about to pull the trigger on a solar install. I've had 10 quotes (yes 10!).

My home setup is:

  • 12kw Vaillant Arotherm Air Source Heat Pump
  • No gas supply
  • Likely to use 10,000kwh per year (This is my first year with the ASHP so this is fag-packet maths based on converting previous gas consumption against my ASHP COP)
  • Peak daily consumption was in January (78kw)
  • Average consumption per day (kwh): Aug (10), Sep (20), Oct (28), Nov (39), Dec (39), Jan (47), Feb (42), Mar (26), Apr (20)
  • Likely to be able to fit 10 panels on the North facing roof, 10-12 panels on the south aspect
  • I have Home Assistant

This is the quote I'm likely to go for:
  • 20 panels (Trina Vertex)
  • 10.8kw total inverter capacity Solax inverter (a 7.5kw inverter and a 3kw inverter - not sure why there are 2 inverters)
  • 21.6kw Solax battery
  • Bird netting
  • No rewiring to cope with grid failure (waiting on the price for that to follow later tonight)
  • Local firm recommended by a neighbour, MCS registered
  • Visited for initial survey
  • Price - £15,100

Overpriced? Seem like a decent design given our usage? Anything I should be asking to change on the quote before pulling the trigger?
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I would say it’s on the upper end, especially if it doesn’t include whole home backup.

Solax is mid range brand so you shouldn’t be paying a premium for it. Others have had similar systems installed for less.
 
b0rn2sk8 said:
I would say it’s on the upper end, especially if it doesn’t include whole home backup.

Solax is mid range brand so you shouldn’t be paying a premium for it. Others have had similar systems installed for less.
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Thanks - what's a fair price do you think? I'm in Hertfordshire? And if permitted can you recommend a good installer?
 
Freefaller said:
Well my givenergy battery firmware is cooked. Modbus / TCP connections not working. Battery not charging at all either via solar or any commands given. Ugh. Waiting for GE to fix it. I wish I hadn't done the firmware upgrade now despite it notifying me every time I logged on.
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Uh oh. Sad times, which firmware bricked it? The dongle firmware?
 
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