Earth Notes: Solar PV Rent-a-Roof: A Renter View (2022)

Updated 2022-06-26 10:42 GMT.
By Damon Hart-Davis.
How was the experience of using others' roof spaces to put up more solar PV after a decade?
PV and apple blossom on south facing wall
After putting up my own system around 2010, I was keen to put up as much other solar PV as I could as soon as I could, solaring up a couple of other roofs nearby, one domestic, one not. This summarises the experience to date.

This write-up has been provoked by the likely need to hand over one or both the non-16WW systems in 2022 for separate reasons, and being interested to reconcile the finances if nothing else in case the taxman asks!

This provides simple case studies of how such schemes worked for all involved.

Domestic System

The domestic installation was/is on the house of freeholder owner-occupier friends of mine.

The roofline was such that I put monocrystaline on the WSW-facing slope, and amorphous on the ENE slope.

The total installation cost for ~2.6kWp of the entire MCS-compliant system, including labour, VAT, etc, was just slightly under £11k in early 2011. (The book value was put at exactly £11k for simplicity, which therefore doesn't quite cover management time and legals.)

A generation meter only (no export meter) was installed with the system. So exports are deemed to be 50% of generation.

It took some time to get the system properly registered, and the FiT (feed-in tariff) started, and if I recall correctly, several months' revenue (859kWh) was lost. There was quite a lot of management pain all told.

The system went live in about April 2011, but it was not accepted/registered for FiTs until 2011-09-09, and the first payment was then not until the period ending 2012-06-15 received circa 2012-08-24.

An in-home generation monitor didn't get used (from memory), but some of its remains are still wired in at the meter.

By , ie eleven years later, total FiT payments are just over £10k.

The FiT is due to continue until 2036-09-08. The current rate for generation is 60.23p/kWh, and export (deemed 50% of generation) is 4.25p/kWh.

Generation over that time has been a little under 21MWh. This was the whole point of the effort, displacing generation carbon emissions! With luck the system can generate at least as much again in its remaining lifetime. Inverter replacement can be expected at least once — my rule of thumb was a mean life of ten years, but my installations have done much better.

There have not yet been any hardware repair or replacement costs, eg of the inverter. But there has been admin effort such as collecting generation readings quarterly, and allowing access for a meter inspection every two years. Also there is a potential opportunity cost of the capital, ie the money could have been deployed somewhere with a higher return.

So a nominal loss to 2022-06 of maybe £1k including inflation, etc, and maybe something similar again for admin/management costs, £2k total, if the whole system failed/stopped dead right now! That would be roughly £100/MWh cost to date, and maybe at (say) an average of 300kgCO2e/MWh over those years (maybe 6tCO2e avoided), a spend of ~£3/kgCO2e avoided.

Seems like a good deal already to me!

The finances are being assessed now because the home owners want to sell up to move close to ageing parents to look after them. I said right at the start that I wouldn't seriously get in their way if thay needed to move. I had a contract drawn up to be fair and clear. The original contract term was 20 years with the right for early termination eg The Freeholders can buy out the System at any time and terminate this Agreement on a straight-line-depreciation basis for the original book value multiplied by remaining months remaining divided by the Term in months, with all rights/liabilities transferred as for the normal contract end date. To help make their sale as quick and smooth as possible I have offered to sell them the system (and the FiTs) for a nominal sum.

The FiTs still have considerable time to run, and the panels should also have plenty of life in them (though the amorphous ones may fade faster), so with luck the house sale price will be boosted.

The owners have not found the system any trouble, and have been very happy with the free electricity, which is all good! (Getting readings from them and so on has been a breeze throughout, also.) They have also taken some other conservation measures that I have suggested, protecting them quite significantly from utility price rises.

IN PROGRESS

Sources/Links

  • Body of specially-drawn-up contract for domestic 'rent-a-roof' arrangement. Permission is hereby granted on behalf of "the Company" (which paid for the legal advice and wording) to use any part of this contract text under a CC0 licence to help fight climate change.
~853 words.