Noob Solar / battery questions and confusion about potential cost savings?

Magnitio

feelingsuelawley said:

Magnitio said:

With that level of usage, I would suggest doing a very detailed audit of where all the electricity is being used and work out what improvements can be made. We have 2 adults at home most of the day and the highest month in the past year before installing solar was 251kWh. The quickest and most effective environmental impact you can make is working out how you can use less. Out of interest, do you know what your gas usage is over the same period?

Gas:

• Oct 2363 KWh
• Nov 3845 KWh
• Dec 3999 KWh
• Jan 4737 KWh
• Feb 4110 KWh
• March 2713 KWh
• April 1433 KWh

It's a 1930s built semi where most of the house has no cavity in the walls. And 4 people at home every day meaning at least 4 rooms need to be heated.

There's some modern extension with cavity wall insulation, but one of the rooms we were heating is a loft conversion which isn't great.

And to swing back round to your point on reducing consumption, I'm not saying I'm perfect and I do need to get much more granular with monitoring the usage per activity but realistically I'm going to shave 10% off my usage (as a guess) not 50% so for now I am focussing on how to reduce my environmental (and financial) impact at this level of consumption.

Please don't take any of what I say as being critical, I'm just trying to help and offer advice.

On the electcity consumption, 974kWh in March works out at an average of over 31kWh per day. Without seeing the gas usage, I thought that there might be a big chunk of this for heating, but your gas consumption was over 87kWh per day. I obviously don't know your details, but I would think a bigger than 10% saving could be achieved somewhere. Do you have a hot-tub or mine bitcoins? Are there any particularly large consumers? Any reason why March was 50% bigger than October?

I grew up in a 1930's semi and it wasn't until my parents died that I looked into the energy performance of the building. It had about 50mm of loft insulation that we topped up to 270mm. The front of the house was partly tiled, behind which was a wooden frame with absolutely no insulation; a considerable amount of heat was lost through this. Although the fireplaces were filled in, a lot of heat still escaped through the chimney breast, so they were insulated. If you have large rooms, there is the possibility of insulating on the inside. Externally insulating the walls can be difficult (and expensive) with a semi unless your neighbour wishes to do the same. Under-floor insulation may also be possible. Getting a thermal camera to assess where the heat is lost is very useful, but best done on very cold days. There is a fair amount of information on the internet that will help (e.g. https://energysavingtrust.org.uk/advice/solid-wall-insulation/ )

On the subject of heating, do you have a modern condensing boiler? Do you have a smart thermostat and thermostatic radiator valves? Used properly, these can make a reasonable difference. What temperature do you normally have the thermostat set to?

Given your current high level of gas usage (and therefore high level of heat loss from the building), I don't think a heat-pump is a current solution to reduce environmental impact. Solar panels may be, depending on your roof size and orientation. Payback on solar could be just a few years based on your usage and current costs.

Happy to help.

arty688

I'm a bit confused and could have read it wrong but are you saying solar is not worth it because you use too much electric and it won't cover much of your needs?

If so financially the more generated you use yourself the better solar which in your case would be high. Although 10m2 won't get a lot of solar on it . Do you have a big garden ? Maybe ground mount might be an idea?

feelingsuelawley

Magnitio said:
Please don't take any of what I say as being critical, I'm just trying to help and offer advice.

On the electcity consumption, 974kWh in March works out at an average of over 31kWh per day. Without seeing the gas usage, I thought that there might be a big chunk of this for heating, but your gas consumption was over 87kWh per day. I obviously don't know your details, but I would think a bigger than 10% saving could be achieved somewhere. Do you have a hot-tub or mine bitcoins? Are there any particularly large consumers? Any reason why March was 50% bigger than October?

I grew up in a 1930's semi and it wasn't until my parents died that I looked into the energy performance of the building. It had about 50mm of loft insulation that we topped up to 270mm. The front of the house was partly tiled, behind which was a wooden frame with absolutely no insulation; a considerable amount of heat was lost through this. Although the fireplaces were filled in, a lot of heat still escaped through the chimney breast, so they were insulated. If you have large rooms, there is the possibility of insulating on the inside. Externally insulating the walls can be difficult (and expensive) with a semi unless your neighbour wishes to do the same. Under-floor insulation may also be possible. Getting a thermal camera to assess where the heat is lost is very useful, but best done on very cold days. There is a fair amount of information on the internet that will help (e.g. https://energysavingtrust.org.uk/advice/solid-wall-insulation/ )

On the subject of heating, do you have a modern condensing boiler? Do you have a smart thermostat and thermostatic radiator valves? Used properly, these can make a reasonable difference. What temperature do you normally have the thermostat set to?

Given your current high level of gas usage (and therefore high level of heat loss from the building), I don't think a heat-pump is a current solution to reduce environmental impact. Solar panels may be, depending on your roof size and orientation. Payback on solar could be just a few years based on your usage and current costs.

Happy to help.

Valuable feedback, thanks. No criticism inferred, grateful for the info!

According to my IHD, at any given moment, the house is using about 0.5KWh just "ticking over". That's with a random subset of lights on/off, maybe 1 computer on and the usual collection of smart devices/fridge/freezer/microwave/TV box etc etc on standby and no "big consumers" switched on (kettle, oven, dryer etc). I have no idea if that's high, low, average - I'd guess "above average" but I have no insight beyond that.

Overall, I think it's quantity of appliances, not one (or two) big hitters, since all our appliances are as energy efficient as are readily available (A-rated dishwashers, refrigeration etc) and we have LED lamps throughout. We do most of our cooking from scratch, so gas burners and electric ovens are on quite a bit for cooking. Very little "slam it in the oven for 5 minutes" food prep.

But each of us WFH/learning FH are using dual monitors and a desktop PC (but no bitcoin mining that I know of!). We have a tropical aquarium and a garden pond with a pump but the pump is 25W, the fish tank heater is about 125W and neither are on all the time (timer/thermostat respectively)

2 Year old Vaillant condenser boiler, coupled to a Nest smart control system and energy efficient pump to circulate water. Themostat set to 21 in depths of winter, 19 the rest of the time. TRVs in every room. LED bulbs throughout (mostly Philips Hue, so they are "on" permanently and controlled by app/sensor)

Loft conversion is about 10 years old. Insulation under its floor - but won't be 270mm since it's only between beams - and I believe its "ceiling" into the roof is insulated but again not 270mm because the frame it's attached to isn't that deep. I know our roof is usually the first one where the snow melts, although we've reshuffled the use of rooms and the attic is no longer in use 24/7 which will probably help in future.

House is double glazed throughout. Aware of insulation options for solid walls but not been able to prioritise it yet.

As I say, there is lots I need to think about in terms of reducing energy consumption for both gas and electricity, but in terms of the basics - LED bulbs, efficient appliances (LCD not plasma, A ratings etc) - that's all done. The rest is more complex and potentially expensive to do something about, but so is solar.

arty688 said:

I'm a bit confused and could have read it wrong but are you saying solar is not worth it because you use too much electric and it won't cover much of your needs?

If so financially the more generated you use yourself the better solar which in your case would be high. Although 10m2 won't get a lot of solar on it . Do you have a big garden ? Maybe ground mount might be an idea?

I think the thing I need to get my head around is what "good" looks like for Solar for me, given that 10m2 on roof is probably my limit on capacity - and I'm in a conservation area which limits my options to some degree.

I had a hope/expectation/fantasy before reading this thread that I could spend £10K to chuck 10m2 of panels on the roof and a battery which would make me basically self-sufficient and free from the worry of future industry price rises. Then I could also power my (future) EV for free and move hot water heating to electric for free too - while reducing the use of gas/burn fewer fossil fuels etc.

Clearly that's not true, so I need to investigate it a little closer and get more data on what %age of my usage I can actually generate myself through solar and what that means financially.

Since I'm already on a 100% green electricity there's no immediate change in environmental impact just from moving from supplied electricity to self-generated solar - so would solar deliver environmental benefit by allowing me to move diesel/gas to electricity without increasing my costs?

arty688

Since I'm already on a 100% green electricity there's no immediate change in environmental impact just from moving from supplied electricity to self-generated solar - so would solar deliver environmental benefit by allowing me to move diesel/gas to electricity without increasing my costs?

I have no real clue how the energy market works but my thoughts are if everyone changed to a 100% green energy it wouldn't mean all electric is suddenly 100% green and no more gas would be burnt. So I would say the Electric that you actually use is not 100% green so if you generate some yourself you are reducing the amount of gas burnt.

Having said that is the whole process of getting solar panels actually green. If so not sure what the green ROI is. I don't know, which is probably why most people focus on the financials.

andyg9053

If you are comfortable at 19 degrees for most of the year, why turn it up in winter? Every degree lower saves 10 %.

Do you run heating all night, if so turn it down a bit. 

feelingsuelawley

arty688 said:
I have no real clue how the energy market works but my thoughts are if everyone changed to a 100% green energy it wouldn't mean all electric is suddenly 100% green and no more gas would be burnt. So I would say the Electric that you actually use is not 100% green so if you generate some yourself you are reducing the amount of gas burnt.

Having said that is the whole process of getting solar panels actually green. If so not sure what the green ROI is. I don't know, which is probably why most people focus on the financials.

oh heck, don't start me on whole lifecycle environmental impact! 

Might have confused things with my reply:
I currently use mains gas for heating + hot water and Diesel to run my car.

Gas + Diesel I burn has an environmental impact I could take steps to remove, by moving my domestic water heating to electric and my car to EV and using green electricity to do so.

If I do both of those things while using electricity from my supplier, the cost is going to be quite high. In theory, doing so from self-generated electricity is not going to increase my cost (so long as I'm able to meet my own demand)

andyg9053 said:

If you are comfortable at 19 degrees for most of the year, why turn it up in winter? Every degree lower saves 10 %.

Do you run heating all night, if so turn it down a bit. 

It's a reflection of the insulation of the house (and a lifestyle that involves sitting at a desk for hours at a time). If the outside temp is below about 3C, thermostats at 19C don't keep the house warm enough, so they go up to 21C for a while in the coldest periods.

And no, not on 24/7. But on (by timer, if not thermostat) most of the day because of people WFH - the house is never empty.

arty688

heat geek has some good videos on you tube about energy savings

eg https://www.youtube.com/watch?v=lu0k8A7K2kY&t=334s

QrizB

arty688 said:

I'm a bit confused and could have read it wrong but are you saying solar is not worth it because you use too much electric and it won't cover much of your needs? If so financially the more generated you use yourself the better solar which in your case would be high. Although 10m2 won't get a lot of solar on it .

As a very general rule of thumb, the smaller the system the greater thr %age self-consumed. The challenge is that smaller systems tend to cost more, per watt of panel, than bigger ones so it' can be a balancing act to choose a system that's the right size.

In feelingsuelawley's case, 10 sq. m. will accommodate roughly 2kWp of solar panel which is at the smaller end of the scale for an early-2020s solar PV system, but they should be able to use a very high %age of what they generate with it.

feelingsuelawley said:

arty688 said:
Having said that is the whole process of getting solar panels actually green. If so not sure what the green ROI is. I don't know, which is probably why most people focus on the financials.

oh heck, don't start me on whole lifecycle environmental impact! 

Around 3 years is the oftten quoted as the carbon payback time for a solar PV system installed in the UK. Given that a system should have a 20+ year life, it's a significant reduction in whole-life carbon.

arty688

Although I would guess the carbon payback time will increase with the increase in green generation.

QrizB

arty688 said:

Although I would guess the carbon payback time will increase with the increase in green generation.

Yes, but that won't change very much in the next 3 years!