It's not Friday the 13th, but... Part 2

In It's not Friday the 13th, but..., I had a picture of my then new Solar PV installation.

1.35kWp Solar PV using Kyocera 135W panels + 2kWp Solar thermal using 100W Thermomax tubes.

As the Solar thermal tubes were no longer heating the hot water much (they were installed in 1991), I decided to upgrade my system. It now looks like this...

3.5kWp Solar PV, using Hyundai 250W panels.

Of the twenty 100W Thermomax evacuated heat-pipe solar collector tubes, only one still worked.

The limescale-coated bulb at the bottom is very hot!

Hot water is now heated by the immersion heater in the tank in the airing cupboard, using spare electricity that's been generated but not used. This is controlled by a gizmo called an immerSUN. See below. The immerSUN is at top left. The inverter is at bottom right.

The current-sensing transformer is the black thing around the red wire, sitting on the black fuse.

The water from the hot tap is now hot enough to make instant coffee!

As the company that installed the upgrade had previously only installed systems to properties previous without Solar PV, they thought that I would receive the current Feed-In Tariff rate, which is 16.56p/kWh, including 50% export Tariff. This is much lower than the Feed-In Tariff rate that I was receiving for my 1.35kWp installation, which was 47p/kWh, including 50% export Tariff. They suggested that I phone ScottishPower (my energy supplier) for clarification.

The good news is that I will receive 47p/kWh for 1.35kW and 16.56p/kWh for the additional 2.15kW, making a net Feed-In Tariff of 28.3p/kWh, including 50% export Tariff. That's 71% more than I thought I'd get.

Based on PVGIS data (postcode-dependent), the system should generate 3,210kWh/annum. That's £908/annum in Tariffs + ~£240/annum in saved electricity consumption + ~£50/annum in saved gas consumption = ~£1,198/annum. The system cost £7,700 including VAT, so ROI is 15.6%. Feed-In Tariffs increase by ~5%/annum and energy prices increase by ~14%/annum, so the system should pay for itself in ~5 years.