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

feelingsuelawley

QrizB said:

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.

2KWp from 10m2? Damn, I thought it was nearer 4KWp, must have read it wrong!

Thanks ever so much for all the insight and advice @QrizB @Magnitio and co

QrizB

feelingsuelawley said:

QrizB said:

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.

2KWp from 10m2? Damn, I thought it was nearer 4KWp, must have read it wrong!

Full sun is about 1kW/m2 and current-generation panels manage roughly 20% efficiency (maybe a tiny bit more). Efficiency has risen by 7% in the past decade so give it another 30 years and you might get to 40%!

Magnitio

feelingsuelawley said:

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.

I am assuming you mean 500W, which is high, but isn't quite ticking over if computers and other items are on. As an example, base in our house is about 50-60W, but when fridge and freezer kick in it is about 200W. I know some others on this forum would think 50-60W is excessive.

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)

Desktop PC's can consume a fair amount. With 2 monitors and peripherals, that could be 200W. Do they get turned off or put to sleep when not in use? It's worth looking at the Power options (Control Panel\All Control Panel Items\Power Options) and trying them on Power Saver. Laptops are much more efficient if you have that option.

I would also suggest getting an energy monitor and checking out the consumption of everything in the house. I think you'll be surprised at what you find. An example is: https://www.currys.co.uk/products/tplink-tapo-p110-mini-smart-wifi-socket-10230067.html which can also be used to turn sockets on/off. I used one to check our house and found a few things that consumed more than I expected and also adjusted some settings to reduce power usage.

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)

Sounds good, apart from the temperature settings. I know it can be difficult with the family, but wearing a bit more clothing and turning the thermostat down a degree or two can make a massive difference. 18-19 should be achievable.

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 mentioned, a thermal imaging camera can be used to see where the heat leaks from your house and provide you with information to look at solutions. They can be bought or hired.

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.

The other area not mentioned is the amount of hot water used. Showers/baths can be massive consumers of energy.

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?

Although you may pay for 100% green electricity, life's not that simple. For most of the country, most of the time, if you are generating extra load on the grid, it is met by the burning of coal or gas. If you start using your own solar, you are making a difference. Unfortunately, as you have found from other discussions, it looks like you might not have sufficient roof space for a decent solar system.

I've messed up and added comments above..

arty688

Nothing to do with the electric but before turning the stat down check your boiler settings. As the person who installed your boiler has probably had zero energy efficiency training and the factory settings are way too high in most cases. Although its the wrong time of year for any savings.

What's the flow temp to your rads? and do most have TRV's?
What's the hot water temp set at ?

marchesini46

marchesini46 said:

shibli said:

I have a similar quote with Light Renewables but requested a "iboost" for my megaflow, this will save gas costs in heating the water, which current rate has made it worth the investment

I think armed with all this new info, I’m going to give them a call and get a revised cost with more battery, panels and the iBoost. 

Thanks

Resurrecting this old thread but with the news that bills are expected to rise again in a few months, I seriously need to get this install sorted.

One quick question that I hope Octopus customers can answer. I understand that I buy electricity for approx 29-31p per kWh and any extra I generate via solar can be sold back to Octopus for 7.5p per kWh. That seems a huge price discrepancy between the two and while I’m sure it’s not a case of taking my solar energy and then selling it to my next door neighbour for a massive mark up, it still seems a tad miserly. Have I understood this correctly?

I’m not planning on buying an EV any time soon so am limited what night time tariffs I can switch to but seem to recall reading that there is an Octopus tariff that pays you much more than 7.5p per kWh (around 16/17p per kWh) and would assume that if energy costs continue to rise, then would assume that you would in turn get paid more for any solar energy you generate? 

Can anyone explain how the the Octopus export tariffs work? 

Thanks

Boffinboy24

https://www.energy-stats.uk/octopus-agile-outgoing-export/ Has a very good write up 

marchesini46

Boffinboy24 said:

https://www.energy-stats.uk/octopus-agile-outgoing-export/ Has a very good write up 

That’s super useful. A quick read through shows that the export tariffs are between 11p and 20p + per kWh on the Agile tariff (in the SE London area) - which seems pretty decent. 

Are there any strategies that have worked for anyone as it seems like very much a balancing act about the usage cost / export cost.  I was looking at batteries and solar diverters to heat up my Megaflow hot water but wonder if these are a false economy. The only thing I am sure about is that I need to do something 😂 but so confused about what exactly. Even how many panels I can fit on my roof as I’m sure that my roof is large enough to fit more panels on than my current quotes 🤔

Boffinboy24

TL;DR if it’s only about saving money get solar and think really hard before spending money on the other things

The general principle tends to be get as much solar capacity as you can, the cost per kWp will usually go down because scaffold etc form a reasonable part of the cost, and in the winter months you will never generate that much so more panels helps. You then try and maximise self usage by running appliances when the sun is shining, and things like running them one after another rather than all at once if you know it would exceed what you are generating.

For hot water diverters this is primarily about environmental benefit (unless you have solar from the past with “deemed export” which is no longer relevant) and reducing gas use. Even with price rises gas is cheaper for hot water heating, and all you are saving is the difference between gas cost per kWh and the SEG payment you would otherwise get. If you use agile outgoing you’d be losing money as the SEG payment is higher than the gas cost per kWh at the moment. 

For most people batteries have so much uncertainty and are unlikely to pay back anywhere near as fast as solar. The general guidance is don’t do it for savings alone - do it for fun, the knowledge of using your own electricity etc. They may cover their cost in a few years if pricing stays as high as it currently is for longer term, and you have an EV to allow you to get on Go. Or if you are on Tesla energy plan and a fully electric household. Or electricity prices may decline significant in a year or two, Go and TEP may change or be discontinued, and the economics look poor. Many people - including oft-cited YouTubers - forget to take in to account the opportunity cost / cost of capital (eg how much interest you’d earn with the money in a savings account), missing out on higher SEG payment tariffs like Agile outgoing, as well as round trip losses on the battery. A lot would have to fit together for it to really make sense on economics alone over and above solar. There is no strong positive environmental argument, as far as I can tell, because any solar you export is still green energy being used.

arty688

Another benefit of solar is your get a bit of energy independence which will protect you against the some of the volatility in the markets , like what we are experiencing now. Long term I hope price will fall back again but will probably settle above where they were. Tariffs will come and go, I think Go and Agile will end and be replaced by smarter EV and heat pump tariffs which would mean you had to own one as they would interact with the supplier.

markin

If the Garden has room maybe a large pergola roof plus ground mount along a fence line would be the way to go. If it was just the 2 of you working from home, a home office would make perfect sense, Being smaller and better insulated than the house.