Discussion
Really helpful, thank you
So between 5 and 15 kWh per day (accepting the point already made that there will be a big variation between individual days?)
I guess what size array and battery you need depends on whether you are intending to go off grid entirely (I’m not) or just use all your available south facing roof space in a way that allows you to use most of the electricity and not export much (given how little you get paid for it).
Even with electricity capped at 36p per kWh you’d be generating around £1.5k per year so the system would pay for itself in under 10 years while all the time reducing your carbon emissions?
Thank you for sharing your data.
So between 5 and 15 kWh per day (accepting the point already made that there will be a big variation between individual days?)
I guess what size array and battery you need depends on whether you are intending to go off grid entirely (I’m not) or just use all your available south facing roof space in a way that allows you to use most of the electricity and not export much (given how little you get paid for it).
Even with electricity capped at 36p per kWh you’d be generating around £1.5k per year so the system would pay for itself in under 10 years while all the time reducing your carbon emissions?
Thank you for sharing your data.
It seems pretty clear to me that the viability of solar is dependent on personal circumstances and the addition of a battery can range from pointless to critical.
What’s very clear (to me) is that for some people (myself included) even with grid prices at ‘just’ 34ppkWh Solar is a great investment. For me personally the break even period is approximately 4 years. And for the next 20 odd years after that I will be saving a considerable sun of money.
The only question is timing the install, weighing up current high install prices versus guessing how long high electricity prices will last. My feeling is as long as you are not totally getting your trousers taken down it’s worth going for it sooner rather than later.
What’s very clear (to me) is that for some people (myself included) even with grid prices at ‘just’ 34ppkWh Solar is a great investment. For me personally the break even period is approximately 4 years. And for the next 20 odd years after that I will be saving a considerable sun of money.
The only question is timing the install, weighing up current high install prices versus guessing how long high electricity prices will last. My feeling is as long as you are not totally getting your trousers taken down it’s worth going for it sooner rather than later.
Dave726 said:
It seems pretty clear to me that the viability of solar is dependent on personal circumstances and the addition of a battery can range from pointless to critical.
What’s very clear (to me) is that for some people (myself included) even with grid prices at ‘just’ 34ppkWh Solar is a great investment. For me personally the break even period is approximately 4 years. And for the next 20 odd years after that I will be saving a considerable sun of money.
The only question is timing the install, weighing up current high install prices versus guessing how long high electricity prices will last. My feeling is as long as you are not totally getting your trousers taken down it’s worth going for it sooner rather than later.
Four years is an incredibly short break even point. What do you base that on?What’s very clear (to me) is that for some people (myself included) even with grid prices at ‘just’ 34ppkWh Solar is a great investment. For me personally the break even period is approximately 4 years. And for the next 20 odd years after that I will be saving a considerable sun of money.
The only question is timing the install, weighing up current high install prices versus guessing how long high electricity prices will last. My feeling is as long as you are not totally getting your trousers taken down it’s worth going for it sooner rather than later.
15p export rates from Octopus are going to be nice for some:
https://utilityweek.co.uk/octopus-energy-doubles-s...
https://utilityweek.co.uk/octopus-energy-doubles-s...
MaxFromage said:
15p export rates from Octopus are going to be nice for some:
https://utilityweek.co.uk/octopus-energy-doubles-s...
That could change the game significantly.https://utilityweek.co.uk/octopus-energy-doubles-s...
Obviously, you'd need to compared the whole of the tariff with other tariffs.
MaxFromage said:
15p export rates from Octopus are going to be nice for some:
https://utilityweek.co.uk/octopus-energy-doubles-s...
Interesting. I do find the Octopus tariifs a bit confusing. https://utilityweek.co.uk/octopus-energy-doubles-s...
What does that mean in practice? Octopus do seem to have high import rates 40-50p? (which might be OK depending on set up) - but are you still able to get cheap night rate leccy too - e.g. the 7.5p for 4 hours rate as well as 15p export? If not isn't the winter potentially expensive?
In this case, what are the other rates alongside the 15p export?
I'm still procastinating over adding a 2nd battery.
We burn, on a rolling 12 month average, 16kWh of electricity per day
A single 5kW inverter can put 14.4kWh of juice in the battery in a 4 hour (off peak, say), period.
I reckon we'll be producing way over that from solar during 6 months of the year - but obviously there will be higher & lower production days.
The only downside of an extra battery is the £. But the upside is it'll reduce our peak time grid consumption and smooth out the summer months production a bit more too. But it is a chunk more £ - and while I'm not doing this just for the savings & payback, I'm doing it because I'd like to minimise grid consumption at all. It's like deciding between an S6 and an RS6 (if they still make both, I dunno).
We burn, on a rolling 12 month average, 16kWh of electricity per day
A single 5kW inverter can put 14.4kWh of juice in the battery in a 4 hour (off peak, say), period.
I reckon we'll be producing way over that from solar during 6 months of the year - but obviously there will be higher & lower production days.
The only downside of an extra battery is the £. But the upside is it'll reduce our peak time grid consumption and smooth out the summer months production a bit more too. But it is a chunk more £ - and while I'm not doing this just for the savings & payback, I'm doing it because I'd like to minimise grid consumption at all. It's like deciding between an S6 and an RS6 (if they still make both, I dunno).
TDK-C60 said:
Interesting. I do find the Octopus tariifs a bit confusing.
What does that mean in practice? Octopus do seem to have high import rates 40-50p? (which might be OK depending on set up) - but are you still able to get cheap night rate leccy too - e.g. the 7.5p for 4 hours rate as well as 15p export? If not isn't the winter potentially expensive?
In this case, what are the other rates alongside the 15p export?
I believe you cant be on Go and the cheap export. I think you can be agile but not 100%What does that mean in practice? Octopus do seem to have high import rates 40-50p? (which might be OK depending on set up) - but are you still able to get cheap night rate leccy too - e.g. the 7.5p for 4 hours rate as well as 15p export? If not isn't the winter potentially expensive?
In this case, what are the other rates alongside the 15p export?
You say the only downside is £, but they are quite a lot of £
We have a similar average consumption to you and specified a 15kw battery, but I have the feeling the payback vs a 10kw would be hard to justify. At the moment we use 50% of the battery per night, but it is going up daily as the days get shorter.
It all seems to be diminishing returns, especially when the elephant in the room is our gas consumption.
Last year we consumed 5,500kw of electricity but 38,000 kw of gas
We have changed our hot water to a heat pump, but cant find a solution for the central heating. We have those old-fashoined (1970s) radiators in the floor which require high temperatures to work, and heat pumps cant produce the temperatures required.
We have a similar average consumption to you and specified a 15kw battery, but I have the feeling the payback vs a 10kw would be hard to justify. At the moment we use 50% of the battery per night, but it is going up daily as the days get shorter.
It all seems to be diminishing returns, especially when the elephant in the room is our gas consumption.
Last year we consumed 5,500kw of electricity but 38,000 kw of gas
We have changed our hot water to a heat pump, but cant find a solution for the central heating. We have those old-fashoined (1970s) radiators in the floor which require high temperatures to work, and heat pumps cant produce the temperatures required.
I hear you. I fear the 9.5 might not be enough - I could go halfwayish to 15, but in for a penny in for a pound, I'd prob go straight to 19.
We won't be able to do a heat pump either - our house just needs a lot of heat to keep it warm. So 2x log burners and 2x open fires to supplement the gas is the best I can do for now. And the idea is dump some excess solar electricity into the immersion to reduce gas a bit.
Very similar gas numbers to you too.
We won't be able to do a heat pump either - our house just needs a lot of heat to keep it warm. So 2x log burners and 2x open fires to supplement the gas is the best I can do for now. And the idea is dump some excess solar electricity into the immersion to reduce gas a bit.
Very similar gas numbers to you too.
AW10 said:
julian64 said:
Anyone seen solar panels with built in inverters yet?
What would the advantage be?Batteries are DC and the grid is AC - as batteries become more common that seems all the more reason to stick with DC from the panels.
Arnold Cunningham said:
I hear you. I fear the 9.5 might not be enough - I could go halfwayish to 15, but in for a penny in for a pound, I'd prob go straight to 19.
We won't be able to do a heat pump either - our house just needs a lot of heat to keep it warm. So 2x log burners and 2x open fires to supplement the gas is the best I can do for now. And the idea is dump some excess solar electricity into the immersion to reduce gas a bit.
Very similar gas numbers to you too.
Have you looked at your expected usage on an hour by hour basis and how a battery supports that? It is worth doing.We won't be able to do a heat pump either - our house just needs a lot of heat to keep it warm. So 2x log burners and 2x open fires to supplement the gas is the best I can do for now. And the idea is dump some excess solar electricity into the immersion to reduce gas a bit.
Very similar gas numbers to you too.
I think our optimal set up will be an approach with 8-10kW solar, using the low tariffs for ~4hours in winter and assigning some high demand activities to that period also, as well as topping up the battery.
If you look at big uses like washers and possibly immersion - this can be done during that 4 hour period - in winter there is no point charging the battery from grid and back out of the battery (remember 5-10% conversion losses) for those uses - just take it direct. Overall you might conclude the battery size you need is not as big as expected. I was originally wondering if 20kW of batteries might be useful, but now thinking 10kW is plenty - at least until I might decide to fully bin gas and go all electric with heat pump - then more batteries might be a consideration. But lots of other house changes needed before then.
This balance also applies to EV charge periods. In winter - use cheap grid, in summer let the PV do what it can. I'd expect PV to easily cover 3/7 days commute in summer. The batteries can really help in some circumstances, but the more you model it the more it seems maybe 6-8kW of battery is plenty "bridging" needed for a typical house.
I'm still doing the sums but breaking use down hourly for winter and summer scenarios is definitely worth plotting out as it changed my view - and look at moving your high energy demands around.
Also worth looking at things like smart immersion when considering overall energy - cut power to only heat to 40deg 15 days only use 60deg for legionella twice a month. The energy savings from this alone could be considerable - cut from e.g. 5300kW per year to 2800kW - and if tank / pipes well insulated much of that power can be taken during 7p rate. (This is going from a 7kW day demand to 3.6kW of 14 days lower demand).
Elec - water heating (annual)
35p - 5300kW is £2800 - baseline - no point - stick to gas
35p - 2800kW is £930 - ignoring >50% could be PV via battery
7p - 2800kW is £261 - ignoring >50% could be PV via battery
The daily amount of3.6kW for low heat days (7kW for kill legionella day) - PV can cover much of that for much of the year - hence reducing grid use/costs
AW10 said:
julian64 said:
Anyone seen solar panels with built in inverters yet?
What would the advantage be?Batteries are DC and the grid is AC - as batteries become more common that seems all the more reason to stick with DC from the panels.
julian64 said:
Anyone seen solar panels with built in inverters yet?
Not built in, but meant to be attached directly to the panels.https://enphase.com/installers/microinverters
Last I heard, Analog Devices were doing cell-level MPPT if you want highest efficiency.
Rough guide is panels that might get shaded, or point in different directions should be parallel, if you have a good array of unshaded panels pointing the same way, series is more efficient due to lower ohmic losses.
But multiple strings are more robust, you don't lose everything from one rifle bullet or small meteorite.
Rough guide is panels that might get shaded, or point in different directions should be parallel, if you have a good array of unshaded panels pointing the same way, series is more efficient due to lower ohmic losses.
But multiple strings are more robust, you don't lose everything from one rifle bullet or small meteorite.
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff