With solar panels, what's the best way to I manage power ecologically?

  • 9 September 2020
  • 7 replies

We have the full wack 4kw  solar panels. My thinking was, it would be best to use the washer, dryer and dishwasher during the day when it’s bright (free electricity will always be cheaper than off peak!). But someone told me that probably wouldn’t work and I should set timers so the machines work at night when it’s cheap (not the dryer - could be a fire risk). How do I calculate when it would be most energy efficient to use the machines?

Also, we work from home so in the winter heating is needed all the time.  We have gas central heating and what we do is have that on in the morning and evening, but during the day use electric fan heaters (hopefully being solar powered) in our two offices. Is that the most efficient and ecological way? (I don’t mind doing the calculations, but I don’t know what they should be!).

7 replies

I’m sure others with direct experience will chip in, but meanwhile…

4kW isn’t a whole lot of heat for two rooms in winter, but could be sufficient depending on your insulation. However, you probably won’t get any (significant) output from the roof in winter! So then gas seems like a better bet.

An air-sourced heat pump gives you about 5 times the heat output as the energy you put in, so could be an option. Read @RoyTheBoy’s experience with heat pumps.

Depending on the deal on the panels, you probably do get free electricity in the sunny daytime, so I’d have thought that’s the time to do the laundry. Not sure where the logic of the somebody comes from, seems counterintuitive. 

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Hi i would ditch the fan heaters and spend time getting the central heating to work more efficiently. Battery storage is better than exporting any spare electric. 

Space out your uasge so that you dont exceed what the solar panels can produce. 

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Bear in mind that there is currently no off peak rate with Pure Planet. So definitely use electricity during the day. Run one appliance at a time - if you want to be very careful, only boil the kettle when you are not using the dishwasher or washing machine, for example. Or to put it another way, space out your usage!

I am surprised that air pumps give a five fold increase in efficiency, I thought it was nearer two fold but I defer to the experience of others. In cost terms mains gas is still the cheapest overall source of space heating in winter,  and I am not sure whether the battery storage of solar power is yet financially viable given the current capital cost and limited life of the batteries available.  I suggest you use your solar power in the warmer months when the sun shines and the gas at other times.  The equation may change when we are eventually allowed to sell our excess domestic wind and solar at commercial rates to energy companies, but don’t hold your breath!!!

Yeah @Daved, it surprising but Daikin quote: 

Air-to-air heat pumps

Our air-to-air heat pumps are powered by around 80% energy extracted from the air and 20% electricity, giving you low-energy cooling and heating for the perfect home environment.

Makes electricity a similar cost to gas to heat your rooms.

Yes, I am still very sceptical. Air source heat pumps are most efficient when there is a high external air temperature, mid summer, when you don’t want the heat for space heating. Far less so mid winter. Worth checking some independent internet sites for the overall figures.  Having said that, there is clearly an environmental benefit compared to mains gas if the electricity comes from renewable sources.

You are right! I’ve worked in an office heated by these things, they are suboptimal during the coldest weather as they have to periodically switch to a de-frost cycle. Ground (or river) source would be better but a lot more expensive.