Calculating Solar PV Savings

Decent enough week 170 kWh.. but the good part is that I used 70% of it which is very good for me. Up until I got the EV I was only averaging about 40-45% self consumption. Worked out the EV is saving me about €270 per month in fuel costs based on the 9 weeks I have it.

Must put together a spreadsheet to work out my savings every month with the PV and the EV.....I love a good spreadsheet!

Why so? Perhaps he might need to charge during the day. Surely you must factor savings during the day usage as well. Otherwise you might as well tell him he can only factor the cooking when done at night, the washing when done at night, etc.

The point is, savings are based on night rate if a device or car can EASILY be used or charged at night.

I think it's fairly safe to assume that 95% of cars can and will be charged at night. Timers can be set in car, or on many chargers themselves.

Charging a car during the day, for most part, should be seen as a nice bonus, but in essence, that power is better served against getting you to midnight to avoid importing expensive units.

Technically your correct deravarra, but to look at it another way......would you charge your car every day during the day if you DIDN'T have solar and a day/night meter. No, you'd plug it in when you go to bed and use night rate. It's basically whatever time was the "normal" use for that component when you didn't have solar.

Washing machines/dish washers the same. If you have a timer and used them at night before getting in solar, then you should count those as night rate. Some people don't like running appliances at night, others don't have a delay timer facility and have to run them at day time. Then sure, that would be day rate as it's what you normally would have done without solar.

Ultimately, it's your math, if you want to fool yourself into thinking that your savings €3000/year, that's up to you. :-)

Again ultimately it's up to you - but the normal way that people work savings is directly applicable to the solar installation. If I have a washing machine and I run it during the day, and then I get a D/N meter in and then run it at night to generate saving......is it fair to attribute that to a solar installation that I didn't purchase? it's nothing to do with solar - I just moved it from daytime to night time.

Basically the kind of standard way that most people here look at solar savings it, is what savings have I generated directly related to the solar. To go back to the washing machine, if i ran it at night before I got in solar and then run it during the day to take advantage of the sun, really I'm only saving the night time rate. If I didn't buy the solar, I would have run it at night time, right?

For your example, if before you had a diesel and then got in an EV, I think it's fair to give an average diesel price/liter. UNless you are the type of person who goes to the local station cause it's handy even though it might not be the cheapest (I do that myself). Whatever the norm was "before" you got in solar.

True the move to EV wouldn't be cheap, but it depends on what forced it. For example, if your existing car just went BANG(TM) and you needed to replace it or spend a fortune, it might not be too bad.

Depends, we got a 2nd hand Leaf and save €1200 a year on juice. And €500 in tax. Ok, I could have bought an old diesel and reduced both, as in I didn't need an EV for it. But can spend as little or as much on an EV as you want. Ours is largely a Leinster Car(TM), and once we accepted the limitations of that we were grand. Of course we can go further but only does 150k before a charge.

**(After writing this I am thinking this whole conversation might be better in a new thread as we are going off topic of daily production but there we go anyway)

Here are my calcs for how much I have saved by switching to an EV over the last 10 weeks. Before we start my previous car was a 2020 (201 Reg) 1.6l petrol Tiguan R-Line that was on PCP with VW. The Tiguan was my 3rd PCP deal with VW and I was paying about €610 pm for this, I went into VW and did the deal and they gave me an ID4 GTX Business for €450 per month with no additional deposit. So straight up I am saving €150pm in PCP loan...for that alone it was worth it. I am not including the PCP finance in my calcs.

The basis of my calculations are below and are simple enough really

Totaled up how much electricity I put into the car (only at night rate) including all external chargers ( a few of these are estimates French chargers so hard to get the data too lazy!) but within a few euro then divided by my total KM. Giving me €0.034 cent per KM.

I then used 7.7l/100km for the fuel efficiency of the Tiguan, this off the internet as I don't know what it actually was but it should be around this or worse.. Then found out how many liters of petrol that would have cost me (at €2.00/litre, its less now but over the last 10 weeks it was around that price) and one minus the other gives me a saving of €717 over 9.7 weeks, which is about €295/pm saving.

I need to do this every month to be accurate going forward as electricity prices are going up and petrol is volatile as well.

Am I right!!!

As far as I am concerned it is good to know and it matters....if you are going to make any significant capital investment you have to compare it to the counterfactual (what would be my cost if I did nothing and still use the ICE car) I did an initial rough calculation but out of curiosity I decided to do a more detailed calc. I get comfort knowing that yeah this month I saved this because I have an EV instead of an ICE. I will probably get board of doing this in a couple of months but I only have the EV 10 weeks now so its good to know.

Also we are all involved here in an online discussion forum where we share info and there are people on here who don't have an EV or PV panels but are researching if they should get one. I always find it every useful when people share their numbers, experience and performance of their systems. Yes some of us can go over board with excel sheets and graphs and logging every bit of data but its like a hobby 😋 doing excel sheets and Home Assistant dashboards.

A year ago when I did it, it was simple. Contact ESB schedule them to upgrade to day night. The provider was sse and didn't do anything in my case.