Calculating solar energy production vs usage

Antonio101

Hi all
Sorry if this has been done before but i am new to solar. I had a 5.7kw array installed with pigeon proofing for £4950 which i dont not think is bad. Very pleased with it as om these sunny autumn days we are producing approx 17kwh and 7kwh on very dull days. Looking forward to summer. We got a phev the next day so our electricity usage has obviously increased.

My query is how do i calculate my savings/usage. I dont current have online monitoring but this will be fitted.

 As you can see my production thus far over 13days is approx 177kw. My smart meter tells me i have exported 84kw. Does that mean i have used 93kwh of what i produced or 53%. On my current tariff this would equate to savings off circa £20.

Now this 93kw, does it simply displace what i would have imported? 

When looking at my in home display it may state for example today is 20kwh. Is this actual import or usage? if for example i used 10kwh of solar is that part of the figure i.e. 50:50 import/solar.

Hope that makes sense. Appreciate any help. Cheers

QrizB

Antonio101 said:

Hi all
Sorry if this has been done before but i am new to solar. I had a 5.7kw array installed with pigeon proofing for £4950 which i dont not think is bad. Very pleased with it as om these sunny autumn days we are producing approx 17kwh and 7kwh on very dull days. Looking forward to summer. We got a phev the next day so our electricity usage has obviously increased.

My query is how do i calculate my savings/usage. I dont current have online monitoring but this will be fitted.

 As you can see my production thus far over 13days is approx 177kw. My smart meter tells me i have exported 84kw. Does that mean i have used 93kwh of what i produced or 53%. On my current tariff this would equate to savings off circa £20.

Now this 93kw, does it simply displace what i would have imported? 

When looking at my in home display it may state for example today is 20kwh. Is this actual import or usage? if for example i used 10kwh of solar is that part of the figure i.e. 50:50 import/solar.

Hope that makes sense. Appreciate any help. Cheers

Congratulations on the new system!

Yes, you've got it right.

• Your generation meter measures how much solar electricity you generate. 177kWh over the past 13 days isn't bad; that's 31 O's (31x your nominal system power). You'll see a thread called "Talking 'bout my generation" where other PV owners (like me) report daily on their output, in terms of O's.
• Your smart meter "Total active import" reading measures how much you import from the grid.
• Similarly, the "Total active export" reading measures how much you have expored to it.

Your self-generated electricity consumption is (generation - export). If you've generated 177kWh and exported 84kWh then you have consumed 93kWh. Similarly your total consumption for the period is (import - export + generation).

Yes, the 93kWh you've generated and consumed has simply displaced 93kWh that you would otherwise have imported from the grid. At 20p/kWh that would have cost £18.60 so that's a saving.

Your smart meter in-home display measures import, not consumption. If it says 20kWh, that's 20kWh imported from the grid in addition to however much electricity you have generated and self-consumed. If the display says 20kWh plus you've self-consumed 10kWh, that's a total of 30kWh you've used in the period.

Hope this all makes sense, if you have more questions ask away!

QrizB

PS you're the first person I've seen with a smart generation meter!

I guess you're getting an account with https://metermanager.co.uk/ or similar? It will be good to hear about that

Heedtheadvice

The only extra comment I would make about the info posted above is the saving can be misconstrued!

That 93kWh saved is correct but only if you have not increased consumption over what you would have done previously.

It's a bit like buying something in the sales to save money...that you would not have bought anyway!

If for example you have the mindset that you are generating all this power so are tempted to use a bit more then you are potentially eating into your saving. Hopefully most of us interested in being Green and Ethical posters are not of that mindset.

Similarly on a total costing basis and considering the the loss of cash to buy a system that could otherwise have been invested there is also a good chance that investing might have generated more income and thus been of more benefit (financially) than the calculated saving.

All that does not affect the calculation above but might put it in financial perspective. Great though that you will be generating and probably saving using fossil fuel yourself or via your export to everyones benefit. Even better when you can charge your car too and I hope you do that in a smart way too to limit what you need to import by using as much of your free generation as possible!

Well done!

Antonio101

QrizB said:

PS you're the first person I've seen with a smart generation meter!

I guess you're getting an account with https://metermanager.co.uk/ or similar? It will be good to hear about that

Hi thankyou for such a detailed response. I needed the confirmation. Sadly i could not be home for the demo.

Yes i do but my device is missing key details so need to message meter manager.

Next steps for me are a 2nd ev, zappi to tap into that excess solar and possibly either a domestic 1.5kw turbine to hybridise my system  or batterys. I think the recent increase in energy costs has changed alot of payback equations

Antonio101

Heedtheadvice said:

The only extra comment I would make about the info posted above is the saving can be misconstrued!

That 93kWh saved is correct but only if you have not increased consumption over what you would have done previously.

It's a bit like buying something in the sales to save money...that you would not have bought anyway!

If for example you have the mindset that you are generating all this power so are tempted to use a bit more then you are potentially eating into your saving. Hopefully most of us interested in being Green and Ethical posters are not of that mindset.

Similarly on a total costing basis and considering the the loss of cash to buy a system that could otherwise have been invested there is also a good chance that investing might have generated more income and thus been of more benefit (financially) than the calculated saving.

All that does not affect the calculation above but might put it in financial perspective. Great though that you will be generating and probably saving using fossil fuel yourself or via your export to everyones benefit. Even better when you can charge your car too and I hope you do that in a smart way too to limit what you need to import by using as much of your free generation as possible!

Well done!

Hi heedtheadvice
Our consumption remains the same but we now have an ev and soon to get a second. The plan is to get a zappi to tap into that excess. I will then look at my total export/use and do some crunching to ascertain if a battery or wind turbine maybe beneficial. 

I likely would have made more throwing this money into s&s but with ever increasing energy prices the ROI is only ever improving. Also the personal pleasure obtained from not handing my money to greedy oil companies, helping holt climate change and being partly energy is a huge return on its own

Heedtheadvice

An excellent ethos!

The financial aspects I only mention because (from just that point of view) it should be considered.

If and when you go for a Zappi make sure you get three CTs so as to monitor grid, EV and generation. Also make sure you have at least a 60amp incoming supply (most usually are) some do happen to be labelled 100A on the fuse holder but are only rated at 60. Make sure you factor in a potential upgrade to your consumer unit if it does not currently have spare capacity/breaker slots.

Early Zappis did have a few teathing problems according to web info but I have been very happy with mine and support has been great. There are others of course that can work out cheaper so maybe worth considering too. For grants you need to get a smart one and are installed by approved installers.

Antonio101

Heedtheadvice said:

An excellent ethos!

The financial aspects I only mention because (from just that point of view) it should be considered.

If and when you go for a Zappi make sure you get three CTs so as to monitor grid, EV and generation. Also make sure you have at least a 60amp incoming supply (most usually are) some do happen to be labelled 100A on the fuse holder but are only rated at 60. Make sure you factor in a potential upgrade to your consumer unit if it does not currently have spare capacity/breaker slots.

Early Zappis did have a few teathing problems according to web info but I have been very happy with mine and support has been great. There are others of course that can work out cheaper so maybe worth considering too. For grants you need to get a smart one and are installed by approved installers.

Off course. Thankyou I will consider those factors.

When you mention others what are they? As far as I was aware zappi and solar edge 2:1 inverter? One some days I have produced enough to cover my baseload and charge the car but off course some has gone to the grid.

Heedtheadvice

Quite a few on the market such asEO, Wallbox uk, podpoint etc.

You should maybe read up about them and pros and cons as well as costs.

Which? Has a good intro to car charging https://www.google.com/url?q=https://www.which.co.uk/reviews/new-and-used-cars/article/electric-car-charging-guide/electric-car-charging-at-home and there are lots of other guides such as https://www.google.com/url?q=https://www.apielectrical.co.uk/electric-vehicles/charge-point-brands https://www.google.com/url?q=https://www.theecoexperts.co.uk/electric-vehicles/the-9-best-home-chargers https://www.google.com/url?q=https://www.smarthomecharge.co.uk and more.

I have not studied the whole market as Zappi ticked all the boxes for me but some are half the cost, some not very advanced but still considered smart enough for the grants.

I hope others will post on here as there is a lot of experience on this forum.

beware some of the web sites will be biased and aimed at sales of a limited selection (situation normal) plus some electricity suppliers also have cheap offerings.

worth doing lots of research to make sure you pick one that meets your need on facilities, plug type, thethered or not, price of course, meets grant requirements, fits location, supplies high enough charge rate to be quick enough for you, remote control, interfaces well with solar, progam to use cheap overnight rates in conjunction with supplier needs,.......

Antonio101

Heedtheadvice said:

Quite a few on the market such asEO, Wallbox uk, podpoint etc.

You should maybe read up about them and pros and cons as well as costs.

Which? Has a good intro to car charging https://www.google.com/url?q=https://www.which.co.uk/reviews/new-and-used-cars/article/electric-car-charging-guide/electric-car-charging-at-home and there are lots of other guides such as https://www.google.com/url?q=https://www.apielectrical.co.uk/electric-vehicles/charge-point-brands https://www.google.com/url?q=https://www.theecoexperts.co.uk/electric-vehicles/the-9-best-home-chargers https://www.google.com/url?q=https://www.smarthomecharge.co.uk and more.

I have not studied the whole market as Zappi ticked all the boxes for me but some are half the cost, some not very advanced but still considered smart enough for the grants.

I hope others will post on here as there is a lot of experience on this forum.

beware some of the web sites will be biased and aimed at sales of a limited selection (situation normal) plus some electricity suppliers also have cheap offerings.

worth doing lots of research to make sure you pick one that meets your need on facilities, plug type, thethered or not, price of course, meets grant requirements, fits location, supplies high enough charge rate to be quick enough for you, remote control, interfaces well with solar, progam to use cheap overnight rates in conjunction with supplier needs,.......

Thankyou I will do my research accordingly.
thanks