Sig Energy Solar Installation

[JohnW2]

To clarify, I was asking of their meaning - I have since noted that Self Consumption refers to that from PV and Consumption is from Grid.

Fair enough, but how does "From Battery" (which could have been charged by either PV or Grid) fit into this? Is it perhaps in addition to 'Consumption' and 'Self-Consumption' (i.e. your total actual consumption was 28.98 kWh - 17.72 + 7.7 + 3.56) ?

 

[ericmark]

The battery is charged and discharged many times a day, solar is fixed, and consumption is also reasonable fixed, once you start a washing machine etc, it has to complete the cycle, so the battery is what ensures you don't use grid power when a cloud comes over.

 

[JohnW2]

The battery is charged and discharged many times a day, solar is fixed, and consumption is also reasonable fixed, once you start a washing machine etc, it has to complete the cycle, so the battery is what ensures you don't use grid power when a cloud comes over.

All true, but what is your point?

 

[morqthana]

kWh is very confusing, really should be Joules, it has nothing to do with time in spite of having hour in the name.

kWh is the opposite of confusing, it absolutely has everything to do with time, and is far more useful and informative than J.

If I have a battery containing 5kWh of energy, I know instantly that I can power a 5kW appliance for 1 hour, or a 1kW one for 5 hours, or a 5W one for 1,000 hours. I know almost instantly that if I run a 2.5kW kettle for 2 minutes I'll have used 1/60th of it's capacity.

On the other hand, if I have a battery containing 18MJ I'm not going to know those things, and even if the kettle maker had thought to tell me that the device uses 2500 J/s I'd have a less friendly calculation to do.

Could be worse though - you could quote a 5kWh battery as being approximately 0.427 gigafoot-poundals.

 

[ericmark]

I agree kWh easier to work with 3600 (60 seconds time 60 minutes so 3600 seconds in an hour) so 3600 Joules = Watt-hour. The seconds and hours cancel each other out, a watt is a Joule per second but so easy for people to get kWh and kW mixed up, and very different units.

Today is the first day I have every noted where the battery has lasted until the sun has started to shine, still have 17% left.

There is a thread I started, "Off-peak tariff, does it really save money?" which has a lot of common ground with this one. There is an off-peak tariff Octopus "Go" or British Gas EV both similar, where you don't need an EV to get tariff, and payment for export, if you get it, is rather low, I think around 8p per kWh. And there is Octopus Flex designed for customers with solar panels and batteries, which gives a far better export rate.

But the off-peak for "Flux" is for a shorter time, and a lot more expensive to import. So much is dependent on how long your batteries will last in the Winter. The 4 pm to 7 pm time is the important slot. My records show I will run out of battery around 5 days a year, but clearly you have no records.

Also, my tumble drier takes around 3.5 hours to complete the cycle, and the off-peak with Flux is only 3 hours, so for the last ½ hour it will be drawing off my battery. Looking at Winter, where some days the battery never full charges from Solar, the shorter time can make a difference in lasting until 7 pm or not.

But the off-peak, standard, and peak with Flux are closer together, so the impact of using the three machines for washing clothes and dishes at the wrong time, is not as much. I note the heat pump drier we have, now has connection to internet, so you can look at the solar production and start it even when at work. Ours was before that feature was included, so just delay start timer. And with both washing machine and tumble drier, they tumble the clothes every so often while waiting for the start time.

 

[JohnW2]

I agree kWh easier to work with 3600 (60 seconds time 60 minutes so 3600 seconds in an hour) so 3600 Joules = Watt-hour.

As has been said, Wh are dramatically more useful, easy to understand and easy to deal with' than are Joules, kiloJoules or MegaJoules.

The seconds and hours cancel each other out, a watt is a Joule per second but so easy for people to get kWh and kW mixed up, and very different units.

People obviously make mistakes but, since kW and kWh relate to totally different quantities, the mistake hould be fairly obvious to any 'reader' - just as it would be if one expressed a distance in mph or a speed in miles.

 

[ericmark]

just as it would be if one expressed a distance in mph or a speed in miles.

Very well put, good analogy.

 

[morqthana]

I've seen people refer to the speed of a ship in "knots per hour".

Or who think that a light year is a measure of time.

Basically there's nothing you can do - there will always be people who are confused, and we cannot pander to them.

 

[Munroast]

for those with Solar + Battery and use Octopus - what Tariff are you on ?

 

[ericmark]

for those with Solar + Battery and use Octopus - what Tariff are you on ?

They tell us the Flux tariff is designed for solar + battery, but as yet not been moved to that tariff, there is also their "go" tariff, get paid less for solar, but off-peak costs less. The main thing is what happens in the winter months, the rate from 4 pm to 7 pm means you do not want to run out of battery before 7 pm. There will be some bad days when it does happen, you could charge the battery at standard rate before 4 pm to get past the 7 pm, but what most people want, is to forget about how much is being used.

But there must be a point where getting only 8p per kWh for export is better than paying 36.06p per kWh for import. So battery size, and power used will determine which is best.

 

[Munroast]

If allowed to use 'Octopus Go' (i don't have an EV) I am thinking of combining that with 'Octopus Outgoing'
this should give
15p for all export
8p to charge batteries through the night
26.2p for all import during the day, which should be very minimal

we average about 12kwh per day, so the the night charge + top up during the day (even in winter) should mean we rarely import from the grid (I guess when we are using above 6kw (that is the limit of inverter) will be only time we use from grid, and 26.2 is only marginally above standard tariff


does all that sound plausible ?

 

[ericmark]

The question is, will they allow you to use "Go" without an EV? It asks me to select and when I select solar and battery it only gives me Flux as an option. I went looking at a YouTube video and the rates given were a lot higher for everything, it did say some people have got onto the "Go" without an EV, but you are looking at a minefield of rates, and you would need to do a lot of calculations to work out the best rate.

 

[Munroast]

it does say on the advert that the cheap energy is for your car and your home

I have emailed them so will find out next week, it would be a fantastic combination of tariffs, and I don't see why they would offer such a far better deal just because you are charging a car battery - what difference does it make to them

 

[flameport]

what difference does it make to them

Load profiles, and the fact that the majority of homes do not currently have an EV.
Just as their export / solar / battery / heatpump and other tariffs are all limited to those who have such devices, and therefore will be a small percentage of the properties they supply.

the cheap energy is for your car and your home

It is - all electricity used in the 5 hour window is at the lower rate, so that would include the car and anything else that was in use at the time.
However electricity the rest of the time is more expensive so like the E7 affairs of old, it only makes sense for those using substantial amounts of electricity overnight.

 

[Munroast]

Load profiles, and the fact that the majority of homes do not currently have an EV.
Just as their export / solar / battery / heatpump and other tariffs are all limited to those who have such devices, and therefore will be a small percentage of the properties they supply.


It is - all electricity used in the 5 hour window is at the lower rate, so that would include the car and anything else that was in use at the time.
However electricity the rest of the time is more expensive so like the E7 affairs of old, it only makes sense for those using substantial amounts of electricity overnight.

There are fewer homes have Solar + Batteries than have EVs and the size of solar batteries will be much smaller compared to EV batteries.
800,000 EVs
175,000 who have Solar + Batteries

so why would they just not offer that tarff to who ever asked? I would assume there is a plausible reason, why would you have to have an EV ?

Octopus Go + Octopus Outgoing would be perfect for me
On the rare occasions I would need to use from the grid during the day I would only be paying 2.9p per kwh more than the standard tariff