100% renewable is not 100% renewable

How renewable is our electricity really?

A third of British homes choose to pay a premium of about 5% to buy electricity that is sold as '100% renewable' but what does this mean?

What it strongly implies is that electricity is exclusively renewable and comes directly from a wind farm, solar farm, or some other renewable source. It's a simple and compelling image that most people accept at face-value.

But can it really be true that all these homes are always getting renewable electricity? What about when the sun doesn't shine, the wind doesn't blow, and we're at home with the lights on?

It seems unlikely.

What the data says

From public data we can calculate how much renewable electricity a supplier buys and compare it to the electricity that they sell to their customers.

And the data shows that the electricity is not 100% renewable.

Actually two-thirds renewable

In fact, most suppliers are only about two-thirds renewable meaning that the remaining third actually comes from fossil-fuel or nuclear generators. And, despite claiming to be 100%, the worst supplier we've rated is actually less than a fifth renewable!

Generous accounting

Suppliers currently rely on a loose and very generous accounting practice that allows them to offset fossil-fuels with renewables.

If a supplier has a deficit of renewables and relies on fossil-fuels on one day, they can still claim to be 100% renewable so long as they have a surplus of renewables on another day.

It's like a restaurant advertising an 'all-organic' menu but regularly having to borrow non-organic ingredients from a neighbouring restaurant. They eventually repay the lender with organic ingredients - and claim to be entirely organic as a result - but the food they serve their customers isn't exclusively organic.

The practice is increasingly meaningless because with growing frequency there's too much wind and solar on the grid which makes offsetting easy and an entirely superficial exercise (like the organic restaurant dumping unwanted organic tomatoes on other restaurants during a glut).

We're being held back

The current system of accounting is over twenty years old, when renewables were rare. Now that renewables are so dominant our accounting needs to be updated to reflect three things:

1) You can't sell what you don't have

Selling 100% renewables means you should always have renewables to sell (just as selling an organic menu means always having organic ingredients). Claiming that a surplus of renewables in one hour 'cancels out' fossil-fueled consumption in another is false pretense and we should, instead, focus on eradicating fossil-fuels entirely.

Our accounting needs to reflect the electricity that is bought from renewable generators and actually delivered to customers.

2) Some suppliers are better than others

Serving customers renewable electricity is hard because the wind doesn't always blow and the sun doesn't always shine.

We find that the best supplier carefully buys electricity from a diverse portfolio of generators and delivers its customers electricity that is over 90% renewable.

By contrast, most other suppliers are only two-thirds renewable and the worst supplier is less than a fifth renewable. And this is just the subset of suppliers that market themselves as entirely renewable!

The best suppliers are actively building the practices and infrastructure that are necessary for a highly-renewable grid, and our accounting should acknowledge and reward their efforts.

3) We need to act with urgency

We're still a long way from being truly 100% renewable and any claim to the contrary is misleading at best and horribly counterproductive at worst.

We need a lot more wind and solar, and a huge number of batteries to shift renewable electricity from times of surplus to those of deficit. And to make this happen we need action from every part of the sector including investors, regulators, politicians and - critically - energy suppliers.

Energy suppliers buy electricity on our behalf and we entrust to them the job of making it clean. We cannot afford for the urgency of the situation to be lost in vague or misleading claims.

We need honest accounting that rewards the best suppliers and directs investment to where it's most needed.