Toaster or Grill?

I changed electricity suppliers recently and my new supplier gave me a little gizmo that shows me the detail of my electricity usage.

Since I have toast for breakfast every day I could see that using the grill as a toaster might not be such a good idea. I bought a toaster, therefore. Then I carried out an experiment and gathered these data:

Toaster 3 minutes at 1.3kWh per serving
Grill 10 minutes at 2.71kWh per serving
Electricity costs 12.1 pence per kWh

The toaster has the capacity of two slices of bread while the grill has a capacity of eight slices of bread.

Use Excel to evaluate my decision to buy the toaster that cost me £24.99 to buy. Set out any assumptions you make as part if your evaluation.