Solar install, part 3 (performance)

Read part 1 for more background.

I have now had one cloudy day, and one much more sunny day. This is April 14th and 15th. Bearing in mind that the forecast from the installer was an average of 24.28kWh/day over the year. I expect winter to be much lower, obviously.

Cloudy April day

The cloudy day had a total of 17.9kWh, usage was 47kWh.

Sunny April day

The sunny day had a total of 48.5kWh, usage was 45.4kWh. Yes, we made more than we used!

P.S. After a few days I can see we are typically doing 40kWh to 50kWh most days, the low cloudy day seems to be very much the exception.

What does that mean?

It looks very much like the forecast is, as expected, somewhat pessimistic and I can expect much higher. The 40 and 50kWh days in April suggests we will easily exceed the forecast for the year.

The sunny day is interesting - we made more from solar than we used, even in April. I can't be sure how usage will go over the summer - I expect it to drop noticeably as the heated kitchen floor used a lot in the winter, but also we now have air-con. The air-con is quite low usage at present, but when it is really hot and sunny it will be using more. The good news is those days will have more solar.

It really does highlight the need for the battery (which is on order). With a battery I could have had all of yesterday's power from solar and imported none. That is, quite frankly, amazing.

I have also changed the hot tub, as one of the really high users of power, to heat during the daytime when we have spare solar rather than maintaining temperature all day and night. Especially without the battery - that alone will save £'s a day.

Part 4


  1. "It really does highlight the need for the battery (which is on order). With a battery I could have had all of yesterday's power from solar and imported none."

    That would only be true if the battery had sufficient capacity to see you through the night. Will the one that you have on order be able to store that much energy?

    1. It should do, just, with changes to hot tub usage profile.

  2. What does the hot tub draw? It may be worth considering a Myenergi Eddi if the hot tub power consumption is within its limits. I have a smaller (5.2kWp) system here with a 9.7kW battery. Currently the battery charges first, hot water via the Eddi second and then any surplus is exported. During April the battery has mostly covered night time use and day time peaks. 3.6kWh from the grid so far for April - but then I don't have a hot tub or AirCon.

    1. I genuinely spent a few moments trying to translate "Myenergi Eddi" from Welsh to English before I twigged that it's a product name!


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