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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
I'm wondering why only the 3 batteries quote include 2 inverters but not the 2 batteries?
To keep cost down?
Also I’m not sure if the export limit the DNO (local electricity distributor) sets for export to the grid limits the max. that can be drawn from the batteries even for self consumption.
I think the standard export limit is 4kW, I managed to get 5kW.
RichardTheKing
Member
Don't know but the guy from Givenergy told me 1 inverter 1 battery = 2.6kWh max and 2 inverters with 1 battery each = 5.3kWh max, but no backup from these batteries in case of power cut, will need another battery with a capacity max of 2.5kWh
That's a shame regarding power cut, as in another battery directly coupled rather than through the inverter?
Having looked at it again, the 5.0 givenergy hybrid inverter can handle 5kW- so I'm guessing this actually handle a max of 2.5kWh per battery (2 total) at the same time?
The extra 3kW inverter would then have been for the third battery option as capacity of the first inverter would have been taken?:
WannabeOwner
Well-Known Member
Given how you have tightened up the building I think that would be a good move (might be worth an air-tightness pressure test though in order to have some data to be sure ...)
We built passive house extension (even though the house is basically "poured concrete" and was already very air-tight we deemed it too difficult to convert existing house to Passive House or EnerPHit). We liked the air quality in the new part so much we then retrofitted MVHR to the old part. We didn't have any mushrooms growing on the ceilings! but undoubtedly had some winter mould spores, and condensation on the windows. That has all gone. Air quality much better, and circulation / evening out the heat too. We have reduced old central heating system usage in the old part of the house by about 50%, prefer to light a wood burning stove (passive house model with external air feed). We did consider wrapping [insulation] the old part; cost would be eye watering relative to any savings / improved comfort, and actually I think making sure all windows and doors are really really! air tight, over insulating the loft, and MVHR have done it for us. (But that is on the basis that we are fortunate that our building is inherently far more air tight than typical UK housing stock)
Something I hadn't realised before doing this: the balance of airflow through MVHR is very important. If the incoming air is greater than the outgoing the transfer of heat is reduced (obvious I now realise, but for whatever reason I didn't realise that before). So any leakage reduces MVHR recovery efficiency (IME massively), so air tightness is key. Even a keyhole in outside door makes a noticeable difference, trivial as that may seem.
Key will be whether you can "hide" the air pipes in a retro fit as they are, necessarily, of large diameter. We had fitted cupboards in upstairs bedrooms that enabled us to route some pipes from loft to downstairs rooms.
Wife and I have had no winter coughs or colds in the half dozen years since building the Passive House extension. And that's despite (pre covid) being in an office with everyone around dying of colds and flu! Both of us had Winter colds / coughs every year before that. So comfort and respiratory benefit worth factoring in too.
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WannabeOwner
Well-Known Member
How quickly does your house cool down? Depending on the thermal mass and insulation I wonder if it would be worth "overheating" overnight (to e.g. +1~2C above normal thermostat) on Eco-7 to charge up the thermal-mass and then heating off during the day (or thermostat set to -1C below ideal, so heating cuts in if temperature falls to uncomfortable).
I have underfloor heating and a building that needs negligible heating and has very high thermal mass (all internal walls are dense-block, the brickies hated me!); the response time is so slow that thermostat is useless - a 1C overrun puts so much heat into the floor, and the loss is so slow, that temperature continues to rise.
What I do is to use bog standard thermostat intended for a "Getting up" and "return-in-evening" time intervals. I set a period late in the night to +1C over, day to -1C under, and afternoon / evening to +0C. If we get a sunny winter day that will increase the air temperature (i.e. heating stays off). That only warms the air, once the sun goes in the thermal mass will soak it up and air temperature falls back. If we get very cold period in Winter I can increase the overnight-hours (although in practice I've been too lazy to do that, and on the only properly artic winter snap we had a few years ago the min temperature only fell 0.5C lower than normal ...)
So I wonder if your house would only lose a couple of degrees over, say, 8 day hours with everything turned off whether "overheat" on night cheap-rate would work. Bedrooms would need to be separately controlled I expect
Giv 3 and 5 hybrids are related to theiir solar inversion. They can both handle 2.6 charge and discharge from the battery.
I have 2 hybrid inverters with a 8.3 kWh each, solar goes into the 5hybrid. Nothing in the 3 hybrid. Both charge from the grid at night. Combined 5.2 charge and discharge.
Both can do emergency power supplies, but they need to go to independent CUs (max 2.6). The CUs can have an automatic changeover switch, I've gone with manual. Most installers want to just put in single sockets for EPS.
lots commenting that 2.5 discharge/charge isn’t a practical limit but I’m struggling to understand. If you want battery as an underlying base capacity to help with avoiding peak grid usage, and even if you have solar there will be plenty of days with limited generation so the battery is being leant on heavily. 2.4kw is basically putting the kettle on. so if you have a baseload of eg 3-500w then any single appliance like a kettle/toaster/oven/tumble drier/hair dryer maybe could be beyond the battery and need grid. Maybe they’re for short enough times that its not worth expanding your capacity for? But especially if we start ot get heat pumps, induction hobs etc there will be increased periods that you can’t move to off-peak that can need more than 2.5kw draw across the whole house?
I was thinking even 5kw might be too low!
in my specific case my array is small (2.9kw) and fitted by someone else (we just get the benefit of the electric) so we can’t easily upgrade to more powerful panels and no room for any more. So we’d be using a battery only slightly to use solar excess but also expecting to timeshift offpeak to peak times.
I was thinking even 5kw might be too low!
in my specific case my array is small (2.9kw) and fitted by someone else (we just get the benefit of the electric) so we can’t easily upgrade to more powerful panels and no room for any more. So we’d be using a battery only slightly to use solar excess but also expecting to timeshift offpeak to peak times.
Thanks for the clarification, like someone mentioned before - you do need an inverter per battery to achieve a total charge/discharge of 5kW then?
RichardTheKing
Member
Yes indeed, but on the other hand with the Powerwall, you've got a bigger battery (13.5kW), and get access to the Tesla Octopus Energy Plan which is the most effective one. I have compared the Octopus Go and the Tesla Energy and I have reduce my return on investment by 1 year
. I have aready found 3 accredited supplier in the Northwest with quote and I am now just waiting for confirmation of the leadtime and the physical house check .The most interesting quote for me is the one for £15,750 (for 15 panel - 1 powerwall2 - the gateway - and a 6kW inverter in/out) I have two other one between £15k to £15.5k but with 12 panels.
Yes.
Each inverter can only charge/discharge at 2.6, so 2 hybrid inverters required for 5kw (if you have grid power).
This is assuming no solar. If you have solar the hybrids can fill the gap from 2.6 to 3/5 with solar.
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RichardTheKing
Member
I am not a specialist, but remember what the guy told me: if I need 5.6Kw (or perhaps 5kw) out/in I will need two inverters. but my main concerne not that by was the powercut situation not supported, or you need to add a dedicated battery with a max capa of 2.5Kw.(which definately not enough - I consume 2kwh/day (mainly fridge-light-smart device-computer), then 2.5kwh give me only 1.5 day without cooking and the frustration of not been able to use the 8kwh battery full of energy. This is real shame. I have tried to investigate and I have not find any another suppliers who can provide what the Powewall can do, , this is very strange.
I did look originally at two powerwalls without solar, so this maybe an option similar to you - is the import tariff just for when charging the battery? Do you mind sharing your contact?Yes indeed, but on the other hand with the Powerwall, you've got a bigger battery (13.5kW), and get access to the Tesla Octopus Energy Plan which is the most effective one. I have compared the Octopus Go and the Tesla Energy and I have reduce my return on investment by 1 year
The most interesting quote for me is the one for £15,750 (for 15 panel - 1 powerwall2 - the gateway - and a 6kW inverter in/out) I have two other one between £15k to £15.5k but with 12 panels.
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RichardTheKing
Member
RedMod3
Member
Interesting stats on the Tesla Energy Plan, but with Powerwalls and 5p/kWh, why would I want to pay 10p per kWh, when I will use all the solar I get and consume any extra I need at 5p per kWh? The plan seems expensive. Anyway, this time next week, my first PW will be fully working, let's see how it goes.
RichardTheKing
Member
Yes indeed, it depend of a good number of differents things, first your load (what your consume average wise on a daily basis), if it is very important it will be more important to invest on a good mixt Battery Vs Panel where you need to prioritise your budget more on battery, then you can get anything you can on the 7.5 p low rate during the night but also enjoy the benefits of the solar panel from April to august to get some type of free energy. now if you load is not very high (say 15kWh to 20kWh/day) the mix is going to be different as well as the plan, you need more solar panel and less battery for the same budget and if you got a TESLA energy plan that balance give you more money back than the Octopus Go Plan. all people are in different situation. for me per example, I am traveling a lot and I spend 6 month in UK and 6 monthh outside UK, If I spend more time oustside UK during the winter I do not need a lot of Kwh batteries because I will only consume in winter 2kWh /day and the cost will be no significant enough to justify that investement. My solar panel will give me a good amount a Kwh during the other 6 months (too much) which I can use for the house and the car and one battery will be more than enough to storage the energy needed during the evening. to demonstrate that flow of energy in and out on a monthly basis Vs Batteries +Panel you need to put yourself infront a spredsheet and simulate the best as you can what will be the best sitution for you: More batteries or more panels? or a good mixte between the two?. Octopuss Go or octopus Tesla or an other plan?, which will tell you what will be your Return on investment you need. What will be energy cost increase? the one you are going to forecast on your moddel for the next 10 to 20 years, if your increase is too high from the futur reality your ROI is going to move out but on the other hand if your forecats is too low your ROI will move in.
Going back to the thread title. Are panels worth it?
OH YES!
I generated 41.6 kWh today. That’s the earliest in the year i’ve generated that much since the panels were installed in 2015.
I consumed all but 400Wh. Charged both cars and Powerwalls, heated the hot water, washed and tumble dried, drum clean on the washing machine, pyroclastic clean on the oven and ran the house.
good result
OH YES!
I generated 41.6 kWh today. That’s the earliest in the year i’ve generated that much since the panels were installed in 2015.
I consumed all but 400Wh. Charged both cars and Powerwalls, heated the hot water, washed and tumble dried, drum clean on the washing machine, pyroclastic clean on the oven and ran the house.
good result
