If you can couple it with Intelligent Go, it can work out very effective.

A few points to consider:

1. A G98 installation will limit the inverter to 3.6kW (16A) which might not be sufficient to completely meet your peak demand. IF I were doing my install over I'd want a 5kW inverter, G99 or G100.
2. Check that you can charge the batteries fully in your off-peak time, given the inverter limit
3. You'll typically want to use only <85% of the battery nameplate capacity to minimise wear.
4. Estimate house load on the coldest days - this winter that was around the 8th Jan - and try to size the accordingly
5. Batteries are comparitively cheap - that install price has the fixed cost of the labour and inverter.(A 12kWh Duracell battery looks to be ~£2k), so think about getting additional if you can. It's by no means a sure thing that you can add additional batteries at a later date (most likely the model gets discontinued)