Before you sign a solar PPA.

1Is the yield from a simulation of your roof, with the losses listed?

Fixed solar in South Africa yields roughly 1,400 to 1,900 kWh per kWp a year, depending on where it is, its tilt and its shading. A figure without its losses can't be checked.

2Has it been laid against your half-hourly load, not your monthly totals?

Weekends, shutdowns and lunch breaks decide how much of the solar you use. What you can't use is exported or switched off, and earns little or nothing.

3What loss of output a year is assumed, and does it match the panel warranty?

Panels lose a little output every year. The proposal should use the warranty's figure, not a better one.

4What happens during load shedding and grid outages?

Most grid-tied systems switch off when the grid does, unless they're designed not to. Check whether the PPA still charges you for energy you couldn't receive.

5Is the saving worked out on the energy rates solar replaces, by time of day?

Solar replaces daytime energy. Your fixed, network and demand charges mostly stay, so a saving on your bill's average rate per kWh overstates it.

6Does the proposal count on a lower maximum demand?

Usually it shouldn't: one cloudy afternoon at peak still sets the month's demand charge. Count it only with a battery sized and controlled for it.

7How does the price rise each year, and against what?

A fixed rise, inflation or your utility's increase. Over 20 years, a gap of 2% a year adds up to almost half as much again.

8Do you pay for what you use, or a fixed amount whatever you use?

Take-or-pay terms, minimum volumes and payment for energy you couldn't take move the risk of your own shutdowns to you.

9How long is it, and what happens at the end?

Terms run from about 10 to 25 years. At the end the system may pass to you, be removed, or stay at a new price: know which.

10What does it cost to get out early?

If you sell the site, move, close a line or want to buy the system, the termination schedule sets the price.

11Who pays when the roof needs work?

Lifting and putting back the panels for a roof repair costs money and lost output. The roof lease should say who carries both.

12What's guaranteed, and what do you get if it isn't met?

A guarantee on output or availability is only as good as how the shortfall is measured and paid.

13What security is asked of you?

Deposits, parent company guarantees or a bank guarantee tie up money or credit lines for the length of the contract.

14Who gets the connection approval, and is its cost in the price?

Your municipality or Eskom must approve the connection. Small systems follow NRS 097-2-1, larger ones the grid code for renewable power plants, and the project may need registering with NERSA.

15Will it export, and what is exported energy worth?

Export credits differ from one municipality to the next, and some don't allow export at all. Check the tariff before counting any.

16Who owns the meter and the data, and can you see it?

You need the metered data to check every invoice and the guarantee.

17Has the PPA been compared with buying the system, on the same yield?

With cash or a loan, owning can beat a PPA. Section 12B of the Income Tax Act allows the whole cost of solar PV up to 1 MW as a deduction in its first year, a benefit the provider keeps under a PPA.

18Does the PPA count as a lease in your accounts?

Under IFRS 16 some PPAs contain a lease, which puts an asset and a debt on your balance sheet. Ask your auditor before you sign.

19Who did the numbers?

A vendor's numbers aren't wrong because they're the vendor's, but someone who isn't selling the system should check them.