Solar, Heat Pumps, Home Battery Storage - How far have you or would you go?

[IBZman]

Ok, they say a picture tells a thousand words…

This was my electric use on Saturday. My annual electricity usage is around 30,000 kWH per year - around £10,000 at current UK energy prices. Ridiculous, I know!

In addition, we have gas central heating / water, which also does cooking and heats a pool. Add another £4K.

We’ve only been in this house for 9 months. It’s a fully extended and modernised mid-century house. We love it, but the energy use is insane!

So, I’m thinking solar, heat pumps (for the house and pool), battery storage… the lot.

We already have four large solar panels, but they are 14 years old and probably as effective now as providing a kettle’s worth of hot water given the current energy consumption!

Our last house had a Mitsubishi Heat Pump, which was very effective, at providing heat and water. I know newer systems are even more efficient energy to power output ratio wise.

Tell me about your experience of solar, heat pumps, batteries etc. I’m particularly interested in anyone living in Northern Europe (I’m in southern England).

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[f1eng]

Wow I don't use anything like that much but FWIW this is what I do.

1. I am an engineer and tight fisted so we have always been concious of efficient use of energy since well before it got stupidly expensive and I don't need a smart meter to tell me which appliances are expensive.

2. Our house is 1930s with "modernised", such as it was in early 1980s, insulation added, it had none at all when we bought it.

3. We have a complex roof so not possible to get a big efficient area of solar cells but we fitted a dual system, to minimise the shadow losses, just in time to get the generous payback, we get around £0.61 per kWh for our supply. It only peaks at 3.5 kW in the middle of a sunny day and only generates 20kWh total on a sunny day, it only made about 4.5kWh yesterday

4. I installed a device which directs excess power to a "heat store" which is effectively just a big hot water tank.

5. I used to just charge our Plug-in hybrid when it was sunny but now I have the Taycan it uses a lot more power, both from electricity being its only source of power and because it goes about half as far on a kWh as the PHEV. So I did consider whether to get more cells and a battery system. I need to keep the existing system separate because of my payment contract.

6. The payback time is what you need to calculate for your use. Get some quotes. My original system turned out to be a no brainer - the payback time looked likely to be 10 years but was less than seven.

7. I am an old bloke so when I looked at payback for a new cell and battery system compatible with the remaining roof(s) it wasn't worth it for me.

 

[IBZman]

Wow I don't use anything like that much but FWIW this is what I do.

1. I am an engineer and tight fisted so we have always been concious of efficient use of energy since well before it got stupidly expensive and I don't need a smart meter to tell me which appliances are expensive.

2. Our house is 1930s with "modernised", such as it was in early 1980s, insulation added, it had none at all when we bought it.

3. We have a complex roof so not possible to get a big efficient area of solar cells but we fitted a dual system, to minimise the shadow losses, just in time to get the generous payback, we get around £0.61 per kWh for our supply. It only peaks at 3.5 kW in the middle of a sunny day and only generates 20kWh total on a sunny day, it only made about 4.5kWh yesterday

4. I installed a device which directs excess power to a "heat store" which is effectively just a big hot water tank.

5. I used to just charge our Plug-in hybrid when it was sunny but now I have the Taycan it uses a lot more power, both from electricity being its only source of power and because it goes about half as far on a kWh as the PHEV. So I did consider whether to get more cells and a battery system. I need to keep the existing system separate because of my payment contract.

6. The payback time is what you need to calculate for your use. Get some quotes. My original system turned out to be a no brainer - the payback time looked likely to be 10 years but was less than seven.

7. I am an old bloke so when I looked at payback for a new cell and battery system compatible with the remaining roof(s) it wasn't worth it for me.

Some excellent pointers there. Thank you.

 

[tomw00]

Ok, they say a picture tells a thousand words…

This was my electric use on Saturday. My annual electricity usage is around 30,000 kWH per year - around £10,000 at current UK energy prices. Ridiculous, I know!

In addition, we have gas central heating / water, which also does cooking and heats a pool. Add another £4K.

We’ve only been in this house for 9 months. It’s a fully extended and modernised mid-century house. We love it, but the energy use is insane!

So, I’m thinking solar, heat pumps (for the house and pool), battery storage… the lot.

We already have four large solar panels, but they are 14 years old and probably as effective now as providing a kettle’s worth of hot water given the current energy consumption!

Our last house had a Mitsubishi Heat Pump, which was very effective, at providing heat and water. I know newer systems are even more efficient energy to power output ratio wise.

Tell me about your experience of solar, heat pumps, batteries etc. I’m particularly interested in anyone living in Northern Europe (I’m in southern England).

I use a similar amount to you ~ 22,000kwh. This is my setup:-

• ASHP - underfloor heating on ground and first floor
• 30 solar panels - 10 facing east , 20 west
• 12kwh - battery system using Victron inverter and BYD batteries
• Shareholding in Ripple energy's Kirk Hill Wind farm ( on stream next year )
• Agile Octopus tariff

To give an indication of what is possible here is my bill from last week

I am currently averaging about 9p/kwh.

The caveat to all this is that I am or was a software engineer so have developed a lot of code to optimise the the use of cheap power. I grab a price feed from Octopus and then tell the battery system/Taycan when to charge.

After the power from the wind farm comes online I anticipate my the net of my power bills to be close to zero.

I am happy to answer more questions. I have only really highlighted the key elements here.

Tom

 

[Fonndu]

Here in the US in North Carolina I have whole house solar and use between 800 and 1600 kilowatts a month depending on season. Have 98 cloudy days on average per year. I have a 15.1kwh solar array (48 panels) along with 20 kWh battery back up due to the fact we have 7-10 power outages a year.
I have only the Taycan to charge besides the house. When I researched my system 5 years ago when I installed I wanted to have 40% more production than what is needed to have extra for future electric cars. I drive the Taycan about 5k miles a year and still have over 20% extra production. Eventually we will purchase another electric car that will drive 20k miles a year and we should be able to still break even with production/ consumption. We are very happy with our set up and financially will break even with just the one car within 8-9 years with our current per kWh rate. Also allows us to be energy independent.
Hope this helps

 

[Dabz]

Our usage is nothing like yours - in fact this year is estimated at 500kwh grid use on a 5 bed large house with 3 of us here (2240kwh used so far in total this year)

We manage that low usage with a combination of solar (7kw system) with battery storage (7.2kw storage) meaning since March we've used at most about 15kwh from the grid in any given month (other than Dec/Jan/Feb) - by being clever when we use appliances and being extremely frugal with energy use. It annoys my wife at times when I stop her putting washing on because we're low on battery but it's brought out consumption down massively. Moving from the electric oven to an air fryer saved us an absolutely astounding amount in electricity for example, and we've used our oven about 8 times all summer (can't fit pizzas in the air fryer!).

Having said that, the car has only ever been charged at home when it'll use excess solar only (granny socket, trickle charge on a sunny day when batteries are already at 100%), and all other charging is done at my office where we have fully renewable electricity from source. We have good insulation throughout and it's gas heating which I'm looking to change to heat pump when Octopus release their new device in the new year.

 

[gramorris]

Southern England too. I'm in to solar, have 12 panels and looking to add as many as I can get away with. When we spec'd it up 2 years ago it started with a 14yr payback and was down 4 years once we hit the peak energy prices.

We have a heat pump too and I'd say it really depends on your situation. We have an ok insulated house and once the outside temperature is in low single digit celsius we're paying more than gas - and that's mostly due to the UK's upside down electricity price policy.

Our battery (10kwh) is useful to avoid peak prices, we mostly use it for that as we're in the house all day so using electricity non-stop and in winter the battery just about gets us through a 3 hour peak period. In summer we export excess in peak times. It is an expensive part of the system and if the tech was there it would've been significantly cheaper to have a car capable of V2H on the drive.

We were NET 0 Jun to Aug on ~ 300kWh usage per month. No Taycan until Dec - hence more panels on the way.

 

[bn8959]

I have 15 panels - 8 facing SSE and 7 NNW. The roof pitch is 21d though, so the rears are actually only about 20% lower output than the front.

They went in April last year.

I have one Tesla Powerwall battery too, which has around 13kWh capacity. We use around 6,000kWh/year (although that is pre-EV).

The battery is brilliant, and ensures we can run entirely on night-rate electricity and solar (except for a very days per year.

I have an Eddi hot water diverter, but ive turned it off for now, as with 15p kwh export and 7p/kwh gas, its better to export the excess solar than use it to save gas.

During the summer we are pretty much nett negative energy use (although again thats pre-EV).

Currently with Octopus on ECO7, but will switch to Octopus Intelligent as soon as my Taycan arrives!

Biggest annoyance is the DNO limited me to a 3.6kW inverter, so despite having 6kWp of panels, I cap out at 3.6kW, eg:

I can pull smart meter data from Octopus API in to PowerBI which is nice:

The odd high night use before April '23 was because Octopus failed to tell us that the way Smart meters are programmed to emulate ECO7 is that they are not BST aware and the 7 hour low rate starts at 00:30 not 00:00, so in the summer the ECO7 low rate is actually 01:30 to 08:30!

OP - sounds like you'd need a big PV array and lots of batteries!

Ive not looked in to heat pumps as I have a relatively new gas boiler and my house dosent suit a heat pump (for one thing, I have microbore pipes which is bad for heat pumps).

 

[Dabz]

Ive not looked in to heat pumps as I have a relatively new gas boiler and my house dosent suit a heat pump (for one thing, I have microbore pipes which is bad for heat pumps).

This is the same situation as us - 5yr old boiler and microbore throughout, other than extended and updated areas of the house. Octopus announced a new heat pump that's coming in Dec, specifically designed for the UK market with a higher temperature flow rate and designed as a direct replacement for those with gas boilers including those with microbore piping. It's worth checking out (though replacing a perfectly good gas boiler gives me the same dilemma as replacing a perfectly good petrol car for an EV...it's not the greenest choice)

 

[Poshfpg]

Ok, they say a picture tells a thousand words…

This was my electric use on Saturday. My annual electricity usage is around 30,000 kWH per year - around £10,000 at current UK energy prices. Ridiculous, I know!

In addition, we have gas central heating / water, which also does cooking and heats a pool. Add another £4K.

We’ve only been in this house for 9 months. It’s a fully extended and modernised mid-century house. We love it, but the energy use is insane!

So, I’m thinking solar, heat pumps (for the house and pool), battery storage… the lot.

We already have four large solar panels, but they are 14 years old and probably as effective now as providing a kettle’s worth of hot water given the current energy consumption!

Our last house had a Mitsubishi Heat Pump, which was very effective, at providing heat and water. I know newer systems are even more efficient energy to power output ratio wise.

Tell me about your experience of solar, heat pumps, batteries etc. I’m particularly interested in anyone living in Northern Europe (I’m in southern England).

This is very interesting as we've been having the same discussions and wondered how effective it would be as our electricity usage is 20,000kwh+ (18,000 for the last 12 months but the Taycan has only been there since Xmas). The RSEV set up, EV dealer and YouTuber, while commercial, looks ideal if it could be replicated domestically.

Moving to a full solar set up with batteries seems like the way forward but I need to find a reputable company to price it up, calculate what we can get on our roof and understand the work involved. I'm less focussed on payback, 7-15 years works fine, but more on a degree of energy independence and reduced bills now. I hadn't really thought about a heat pump to replace the gas boiler is that genuinely feasible?

I would be very interested to hear what you end up doing.

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