Home battery energy store & heat pump advice

[Yachtsman]

I know there are a good number of forum members who are or almost self sufficient in terms of electricity, hopefully I can have some valuable advice and product recommendations from you lucky people.
Now that Boris is willing to give grants towards heat pump installation I’m keen to reduce my carbon footprint and improve my energy efficiency. Until now if been reluctant to go down the solar route simply because I have a relatively small roof surface area facing south. I have a fairly large 4 db house which faces east/west with a small area facing south (5m x 6.5m uninterrupted view) although not surveyed I understand is insufficient to support a house of this size. The house is approx 11 years old and has very good loft & cavity wall insulation.
I’m not really interested in feeding energy back into the grid but would love to be able to manage our electrical, heating & hot water needs using a combination of solar, battery storage & heat pump.
Any advice would be really appreciated in terms of pit falls & poor systems to avoid, best systems & best supplier to talk to etc etc.
Thanks in anticipation.

 

[scdoubleu]

You could always go for a dual array/inverter system. That's what we had installed a few weeks ago. Detached double garage with north/south roof, probably similar size to yours, 9 x 385W panels plus 3 kW inverter. Four bed detached house roof oriented east/west, with 10 x 385W panels on the west side and another 3 kW inverter. All tied in to a Tesla Backup GW2 and one PowerWall. DNO wouldn't let us go any bigger .

Take today as an example. Intermittent sun thanks to a mix of low/high level cloud, but panels putting out over 4.5 kW at peak. Still managed to charge the PW from empty to 70%, plus cook lunch, and two loads of laundry. The PW charge will see us through evening cooking/dishwasher and should last until around 6am tomorrow morning. Not bad for late October.

Hoping to be mostly self-sufficient during the summer, even with our 3 heat pumps in cooling mode.

Steve

 

[Yachtsman]

You could always go for a dual array/inverter system. That's what we had installed a few weeks ago. Detached double garage with north/south roof, probably similar size to yours, 9 x 385W panels plus 3 kW inverter. Four bed detached house roof oriented east/west, with 10 x 385W panels on the west side and another 3 kW inverter. All tied in to a Tesla Backup GW2 and one PowerWall. DNO wouldn't let us go any bigger .

Take today as an example. Intermittent sun thanks to a mix of low/high level cloud, but panels putting out over 4.5 kW at peak. Still managed to charge the PW from empty to 70%, plus cook lunch, and two loads of laundry. The PW charge will see us through evening cooking/dishwasher and should last until around 6am tomorrow morning. Not bad for late October.

Hoping to be mostly self-sufficient during the summer, even with our 3 heat pumps in cooling mode.

Steve

Hi Steve,
Thanks for the info, yes that sounds interesting. This house is a dormer at the front (west facing) so not a lot of available roof space, the east facing is better but does have a velux window in the middle.
Barry

 

[scdoubleu]

FYI, we had several quotes from local installers, none particularly inspiring - mostly because they were solar only; battery storage wasn't their thing. In the end we went via the Tesla website, which resulted in a call from another much more clued up supplier, also local.

Steve

 

[Overworked]

What sort of costs were involved in the setup, may I ask? Are your heat pumps ground or air? Vertical or horizontal loops if ground?

Every time I check and look at the figures for my possible setup, it gets very expensive for an uncertain return. Vertical boreholes apparently at £100 per metre and a few hundred metres down and a few boreholes required soon gets very pricy!

 

[Dilly]

I have 28 south facing panels on my main roof plus 5 more south facing and 8 west facing on my annex. I also have two Powerwalls.
my southern boundary is flanked by tall trees which I love but which play havoc with the panels over winter.
today was more cloudy than sunny but even with 2 washes and tumble dries plus charging the Outlander, I still managed to get the Powerwalls from 59% to 91%. I’ll have about 65% left come the morning.
last year I generated 8500kWh drew 2000lWh from the grid mostly at cheap rate and exported 1000kWh
peak rate draw for the year was just under 200kWh

having the Powerwalls minimises peak rate draw. The west facing panels just give that bit extra in the afternoon evening as the south panels wane.
i have oil central heating and have looked into heat pumps. They won’t do me any favours. All my rads will need upgrading and the system would tip me into peak rate grid draw between now and March annually. I have the space for ground source and that’s where I’ll probably end up when the boiler dies.
I’m not going to rush at the moment!

 

[MrBadger]

Until now if been reluctant to go down the solar route simply because I have a relatively small roof surface area facing south. I have a fairly large 4 db house which faces east/west with a small area facing south (5m x 6.5m uninterrupted view) although not surveyed I understand is insufficient to support a house of this size.

Do I take it that you have east/west aspects too?

If so, don't get fixated on south facing. Its not necessary, far from it. Whilst south facing may give peak power, a properly configured dual aspect east and west setup will likely give peak energy. Basically, south facing is peaky, east and west will be less peaky but will give more usable energy than south facing in early and later parts of the day.

What is even more important, is lack of shading. There are ways to mitigate against it, but shading, no matter how small (including an aerial or telegraph wire, will decimate the output from a string of panels. If you have that then you need to ensure that your solar install takes that into account and do the sums on how much they can recover. On similar subject, watch out for being mis-sold optimisers. They are great if used to solve the appropriate problems, but I've seen them sold to solve things that either do not exist, or could be solved far cheaper by a good design. I use to be on the Solar Edge (an optimiser company that sells good products) installers mailing list so saw what use to be pushed by some installers wanting an easy upsell.

Word of warning. Solar PV is a rabbit hole but you can do the sums yourself to validate what is being sold to you.

Another word of advice. It sounds obvious but is easily lost when savings are being thrown around. You cannot save more than you spend on electricity in the first place.

 

[Yachtsman]

Do I take it that you have east/west aspects too?

If so, don't get fixated on south facing. Its not necessary, far from it. Whilst south facing may give peak power, a properly configured dual aspect east and west setup will likely give peak energy. Basically, south facing is peaky, east and west will be less peaky but will give more usable energy than south facing in early and later parts of the day.

What is even more important, is lack of shading. There are ways to mitigate against it, but shading, no matter how small (including an aerial or telegraph wire, will decimate the output from a string of panels. If you have that then you need to ensure that your solar install takes that into account and do the sums on how much they can recover. On similar subject, watch out for being mis-sold optimisers. They are great if used to solve the appropriate problems, but I've seen them sold to solve things that either do not exist, or could be solved far cheaper by a good design. I use to be on the Solar Edge (an optimiser company that sells good products) installers mailing list so saw what use to be pushed by some installers wanting an easy upsell.

Word of warning. Solar PV is a rabbit hole but you can do the sums yourself to validate what is being sold to you.

Another word of advice. It sounds obvious but is easily lost when savings are being thrown around. You cannot save more than you spend on electricity in the first place.

This house is a dormer at the front (west facing) so not a lot of available roof space, the east facing is better but does have a velux window in the middle.
The east facing is a little better but not fantastic due to velum windows.

 

[Fred2]

I have solar panels (7kW, nearly due south) & a heat pump. In the depths of winter on particularly cold / grey days you might only get a few kWh from the panels but the heatpump might draw 50 kWh+ - there’s no way you’ll be self sufficient over the winter months. Even with the maximum number of powerwalls (9) you’d only be able to hold out for a few cold & dark days

Over the year I generate more than I use for heating, but I still use the grid a lot in winter. East/west panels would be a reasonable - having a bit more solar power in the morning, when you want to warm the house up, or late afternoon when it’s cooling down outside.

 

[MrBadger]

This house is a dormer at the front (west facing) so not a lot of available roof space, the east facing is better but does have a velux window in the middle.
The east facing is a little better but not fantastic due to velum windows.

East or West is not a substitute for south facing. But East and West may well be. But if you only have viable east or west, you are going to be down on total energy capacity and pretty short at one end of the day or other. Only individual usage patterns would tell if that would work or not.

For anyone contemplating solar, the goto site is PVGIS - its change a bit since I last used it in anger, but you probably want the grid connected PV Performance tool at

Photovoltaic Geographical Information System (PVGIS)

PVGIS is a free web application that allows the user to get data on solar radiation and photovoltaic system energy production, in most parts of the world.

ec.europa.eu

Enjoy the rabbit hole...

 

[Yachtsman]

East or West is not a substitute for south facing. But East and West may well be. But if you only have viable east or west, you are going to be down on total energy capacity and pretty short at one end of the day or other. Only individual usage patterns would tell if that would work or not.

For anyone contemplating solar, the goto site is PVGIS - its change a bit since I last used it in anger, but you probably want the grid connected PV Performance tool at

Photovoltaic Geographical Information System (PVGIS)

PVGIS is a free web application that allows the user to get data on solar radiation and photovoltaic system energy production, in most parts of the world.

ec.europa.eu

Enjoy the rabbit hole...

Thanks that’s a starting point. I do have a smallish south facing roof(see initial post) and not a large east facing roof. West facing is a complete no go. East is completely uninterrupted view and south has a small chimney in its lower left corner.

 

[Yachtsman]

I have solar panels (7kW, nearly due south) & a heat pump. In the depths of winter on particularly cold / grey days you might only get a few kWh from the panels but the heatpump might draw 50 kWh+ - there’s no way you’ll be self sufficient over the winter months. Even with the maximum number of powerwalls (9) you’d only be able to hold out for a few cold & dark days

Over the year I generate more than I use for heating, but I still use the grid a lot in winter. East/west panels would be a reasonable - having a bit more solar power in the morning, when you want to warm the house up, or late afternoon when it’s cooling down outside.

Hello Fred, I’m expecting to make use of octopus agile when necessary & I can take advantage of any low rates, haha.

 

[gangzoom]

Hello Fred, I’m expecting to make use of octopus agile when necessary & I can take advantage of any low rates, haha.

I persume you have seen Agile pricing lately.

Lots of good info on here, but essentially heat pumps make zero financial sense at present, unless you really really want one just stick to gas its work much better and cheaper.

We'll probably go ground source heat pump, but only if really forced. I cannot see the imaginary government dead line on phasing out gas boilers becoming reality.

 

[Fred2]

Lots of good info on here, but essentially heat pumps make zero financial sense at present, unless you really really want one just stick to gas its work much better and cheaper.

It’s working out for me, with a relatively new (20ish years) home. When my oil boiler died it was about 10k extra to get an air source heat pump instead of other oil boiler, but I’ll get £9k of that back through RHI.

It’s been just over a year since I had the heat pump installed, over that period it has consumed about 6000kWh. I’m currently on the Tesla energy plan at 8p/kWh, so that’s £480 for a year’s heating & hot water (although that like every else, is going up).

I used to use about 1500 litres of oil a year to heat the house, but that was before working from home so I strongly suspect I would be using significantly more oil that that. The price of heating oil varies a lot, but it’s currently at 65-70p/L so I’m saving money, and it would have to go very low (ie lockdown 1 levels) for it to be cheaper to run on oil

 

[Yachtsman]

I persume you have seen Agile pricing lately.

Lots of good info on here, but essentially heat pumps make zero financial sense at present, unless you really really want one just stick to gas its work much better and cheaper.

We'll probably go ground source heat pump, but only if really forced. I cannot see the imaginary government dead line on phasing out gas boilers becoming reality.

I’m not looking to or expecting to save money just the opposite and appreciate the payback on the initial outlay is likely in the region of ten to twenty years. I’m keen to reduce our emmissions and take advantage of any government grants, god knows I’ve paid plenty in over the years.

 

[Fred2]

Hello Fred, I’m expecting to make use of octopus agile when necessary & I can take advantage of any low rates, haha.

Even if those low rates ever return, agile wasn’t the best fit for a heat pump, since the heat pump is adding a lot of consumption that’s not easy to shift (unless you particularly want the heating going at 2 in the morning!).

It’s not like charging the car where you can just do it the next cheap day, if it’s cold you probably want the heating on. In addition a heat pump is quite different to a gas/ oil boiler where you’d have it running an hour here and an hour there - it’s much better if it can run more constantly.

 

[MrBadger]

I’m keen to reduce our emmissions

If you have an inefficient installation, you may well find that the emissions from the build of the equipment and its supply and installation far outweigh any emissions saving that you may have from operating it. First approach, if you have not already done so, is to reduce the requirements for the heating etc in the first place.

 

[Yachtsman]

If you have an inefficient installation, you may well find that the emissions from the build of the equipment and its supply and installation far outweigh any emissions saving that you may have from operating it. First approach, if you have not already done so, is to reduce the requirements for the heating etc in the first place.

Apparently we have one of the most efficient and reliable gas boilers according to the engineer that serviced it 2 weeks ago. I can’t get into the whole emissions cycle thing else I’d probably not bought an electric car.

 

[Zakalwe]

I moved into a new house about three months ago and am now waiting for an installer to put 5.5kWh of PV on the roof allied with a 8.2kWh battery. The roof is south facing and is not shadowed at all...pretty much the perfect roof for PV. The house is less than 2 years old and very well insulated. Any sun at all seems to really heat the house up as there is a lot of glass in the south-facing lounge and kitchen.

There's no real incentive to change to a ASHP...I pay about £40 a month for heating and hot water via the gas boiler. My plan is to charge the batteries during the day and divert any excess power into the cars (Tesla and Peugeot 208e) and into heating the hot water tank. I can also charge the batteries during the Octopus Go Faster cheap periods (mine runs 8:30PM-1:30AM). If this works then I should use zero gas during the summer- no heating and the water heated via PV).

I personally am not convinced that the current generation of ASHP would be suitable. I will reconsider when the ones that can do cooling as well as heating are less costly. Based on the last few years I guess that the need for cooling in Summer will become as important as heating in Winter.

 

[Teddy69]

I'm in a 2 year old house which has a hybrid Daikin boiler? it's air source and gas, no one else go one like this?

you tell it the tariff info and then it decides when to switch from air source to gas as the temperature drops.