#Electric heater with solarpanels

1 messages · Page 1 of 1 (latest)

inner goblet
#

I have an electric heater. It currently charges at night-time rates. I also have solar panels. When I feed electricity back into the grid, I receive an injection payment. I would now like to calculate how much my solar panels need to generate to make it worthwhile to charge the heater during the day using the solar panels.
The data is:

  • Cost of electricity during the day: 18.13 € cent/kWh
  • Cost of electricity at night: 14.94 € cent/kWh
  • injection payment: 3.73 € cent/kWh
  • Heating consumption: 5.5 kWh

So how much do the solar panels need to generate to make it cheaper to charge during the day? And how do you calculate this?

glass escarp
lapis narwhal
inner goblet
#

You're probably right. This is more of a mathematical problem. I posted it on a maths server and the first reply I got was ‘use a calculator man!’. I have calculated this in this way. Heating one hour in daytime cost 5.5 x (18.13-3.73)= 120.23 € cent. Heating during night costs 5.5 x 14.94= 82.17 € cent. So heating during day cost 38.06 € cent more every hour. This corresponds to 2099 W of electricity during the day. Therefore, the solar panels must generate 2099 W to have the same costs as during the night. Is this correct? I want to be sure about this before I start my automation.

twin jewel
#

If you can do it purely on solar you would otherwise return to the grid it will "cost" (aka, don't get back) you 5.5 kWh x 3.73 cent/kWh = 20.52 cent. You don't pay anything for the energy you can use from your PV directly! During the night it will cost you 5.5 kWh x 14.94 cent/kWh = 82.17 cent. So you save 82.17 - 20.52 = 61.65 cents if you could do it purely from solar.

Time has nothing to do with it as you already specify energy, not power. But to see if you can turn on the heater without importing energy from the grid you will have to look at the power. At that moment you need to export more power then the power rating of the heater. If you don't, it will be a mix of free solar and payed grid import. But that rato depends on solar production and what you already use in your house.