Minimum power requirement for charging from home solar panels

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orrery
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Post by orrery »

I can use the Hypervolt on 'eco' setting - where it always pushes 1.4kW minimum, then ramps up if there is surplus. But I have to make the same call as you - "is it going to be continuous sun all day?" - as I don't want to pay more than I can by charging overnight.
It's a tough call. It doesn't take much to drop the surplus solar generation down below 1.4kW then I end up charging with electrons that cost almost 30p each. You need to guarantee that you are getting better than 6:1 ratio of free leccy to paid, or you are better off charging overnight.
Bearing in mind that the clever chargers cost money, I still think that if you have solar PV you may just be better off charging overnight and leaving the solar to offset the extortionate daytime units.
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Perchede
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Post by Perchede »

I am in France with a 6 year old solar install. Solar prices with much higher then and the govenment wanted to promote integrated solar into the roof. Consequently offering premium prices for 20 year indexed contracts. I opted for 100% injection and currenetly get 0.25 centimes per KWh.
On night 8 hour consumption prices I pay between 8.62 and 12.22 centimes with the lower price available for 300 days p.a. The consumption tarrif (Tempo) is currently available and has a hefty 54.86 day taffif for 22 winter days per year. However you can switch provider at any time without penalty.
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hergus
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Post by hergus »

I have been using a 3kW solar array and a Zappi 2 for the past 7 months. Works for me. I also have Octopus GO tariff so I can instruct the Zappi to charge off-peak (during the night) at 5p per kWh. That rate is due for review in August.
Zappi works well with solar as despite the 1.4kWh threshold, it is possible to adjust how much is taken from the grid if it drops below 1.4kWh (you can do this on the app). On intermittently cloudy days, charging tends to stop after a few pauses due to there being less than 1.4kW, so setting a higher level of grid use can be useful, but does mean paying more for the power.
The MyEnergi (Zappi) online dashboard also gives a solar radiation forecast which is handy for deciding whether to try charging, but is no more reliable than any other forecast.
Just to be clear, I have found that letting the Zappi do everything works fine. I don't set anything on the Enyaq (other than occasionally max 80% charge).
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orrery
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Post by orrery »

hergus wrote: Mon Apr 18, 2022 1:13 pm I have been using a 3kW solar array and a Zappi 2 for the past 7 months...

So, can you set the Zappi to 'super eco' i.e. only charge if there is 1.4kW surplus, and have the Enyaq accept it without it flouncing off home in a huff?
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hergus
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Post by hergus »

You can set the Zappi to Eco+ and it will pause if generation drops below 1.4kW. It does a pretty good job of balancing domestic use (you don't want it to stop every time you put the kettle on) with charging. I find in practice that after several pauses it decides you don't have enough sun and stops charging. Might be the car, but I doubt it. Enyaq plays nicely with Zappi if you let the Zappi do the thinking.
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orrery
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Post by orrery »

hergus wrote: Tue Apr 19, 2022 8:37 am I find in practice that after several pauses it decides you don't have enough sun and stops charging. Might be the car, but I doubt it.
You are describing what I'm seeing. I'm pretty sure that it is the car. If you look at the app, the 'start charging' button re-appears. If you click it, there is a bit of a stand-off as the car and charger try to get their act together, the car throws an error say that the operation was possible, then it starts charging.
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hergus
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Post by hergus »

You may be right, in which case the Enyaq might need a good talking to. It is frustrating to not be able to leave them to get on with it without worrying that a few clouds might interfere.
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RichR
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Post by RichR »

There seem to be a lot of adverts for 4kW solar arrays with 5kWh battery and appropriate inverter etc for about £7000. Do people with solar think this is a reasonable starting point for those interested in having some sort of solar system, that might be suitable for at least topping up a car and taking some of the load off the mains supply?

This is just out of interest - we can't have solar on my house unless we get some work done on the roof first as it's unable to take the weight at the moment :(
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MikeJL
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Post by MikeJL »

RichR wrote: Tue Apr 19, 2022 12:37 pm There seem to be a lot of adverts for 4kW solar arrays with 5kWh battery and appropriate inverter etc for about £7000...
That's the size of system we have, although we don't have room for any more panels. There are lots of fixed costs in an installation (eg scaffolding & inverter), so adding more panels if you have the space may not add much more to the price & will reduce the cost per kWh. For me batteries are a must, else most of the power you generate will go back to the grid, for which you'll be lucky to receive £0.05/kWh under the Smart Export Guarantee.

On a dull winter's day our system produced 0.05kWh (50 watts per hour). The best I've seen so far this year is 2kWh. I haven't had the system long enough to see its performance in summer.

Our intention on sunny summer days is to charge the car via a granny cable, thus limiting the draw on the system, with the batteries able to cover any short cloudy periods. Unfortunately, I don't think we'll have our Enyaq this summer to try it out.

If you have an off-peak electric deal & can charge the car sufficiently on that, then charging more at night & selling your excess electricity during the day should cancel each other out (more or less if you can get the best tariffs for both).

We also have ours configured so that it isolates itself from the mains in the event of a power cut & we are able to use solar & battery power to run some circuits until the mains is restored. A standard install of solar or solar & batteries will switch itself off if the mains power fails (to prevent leakage to the grid). In order to guarantee some power during a power cut, in winter our batteries charge from the mains in the afternoon & we then draw that down in the evenings.

To get back to your question, it's difficult to know what the optimum battery size should be as the system performance varies so much through the year & with varying cloud cover. In winter the batteries are hardly used as the house consumes everything produced; come summer I expect the batteries to be fully charged by mid-day & then to supply our needs through the night. And we haven't considered what power you consume & when. Obviously you will get maximum benefit if you can consume power when the the panels are generating the most.

BTW £7,000 seems a very good price for what you have described, I'd get the roof fixed quick :-)
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white67
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Post by white67 »

RichR wrote: Tue Apr 19, 2022 12:37 pm There seem to be a lot of adverts for 4kW solar arrays with 5kWh battery and appropriate inverter etc for about £7000. Do people with solar think this is a reasonable starting point for those interested in having some sort of solar system, that might be suitable for at least topping up a car and taking some of the load off the mains supply?

This is just out of interest - we can't have solar on my house unless we get some work done on the roof first as it's unable to take the weight at the moment :(
Agree you need to get the roof fixed! £7k is good though 5kW isn't much for a battery, but as I mentioned previously it's useful to have the battery allow you to go off grid i.e. it's between your incoming power and your home fusebox.

My installation was handily timed to be while the scaffolding was still up after having had my roof renewed - 30 years of Scottish weather and it was finished.
So, if you need to renew your roof, plan for (shiny new loft insulation and) solar equipment at the same time.
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