We created Sunsave Plus as a way to make solar more accessible for UK homes, breaking down the upfront cost barrier that stops so many people from going green.

And it was important to us that our customers owned their solar & battery systems from day one, so we structured it as an unsecured personal loan (i.e. instead of a roof lease). 

That makes us a bit unusual: we're a solar installer and a regulated finance provider wrapped into one. Before anyone can get their Sunsave Plus contract, they go through an 'underwriting' process – a series of checks to make sure we can responsibly offer them finance.

As a regulated lender, getting these checks right matters. But they also shouldn't feel invasive, slow, or like an interrogation. 

We've spent the last two years making them faster and far less friction-heavy for our customers.

% of lending decisions made automatically, Jan 25 - Jul 26

Here's what underwriting actually involves

To assess whether we can offer someone finance, we need to build a picture of two things: their history with money, and whether the subscription is affordable for them.

To do this, we use information customers give us, supplemented by data from third parties – primarily TransUnion (a credit reference agency) and HM Land Registry – plus our own decision-making algorithms.

It’s very important that we do this carefully. Get it wrong in one direction and we lend to someone who can't afford it. Get it wrong in the other direction and we turn away someone who'd be perfectly fine. Neither is good – for customers or for us.

We think careful automation is good for everyone

Before getting into the specifics, it's worth explaining how we think about this overall.

We believe in doing whatever gets the best outcome for us and our customers. Manual reviews are slower, more expensive for us, have a higher error rate, and risk being subjective as they can be led by human bias. 

That ultimately means higher prices for customers and less consistent outcomes. Automation, done well, is better for everyone.

When we first launched, a significant proportion of applications required human review – but today, the majority are assessed entirely automatically. We keep an eye on things to make sure it’s all accurate, but in most cases a human only gets involved when genuinely needed.

For cases that do need more information, our system now works out what questions to ask and sends them to the customer automatically – instantly after they apply, rather than hours later when someone gets to it. 

Customers get a faster response, and our team only needs to review the reply. It's a much better experience on both sides.

Everything else we've improved has been in service of this: making our process smarter, so fewer applications need a human in the loop.

It all starts with cleaner data

Automation only works if the data going in is reliable. We found that some customers were entering information in ways we didn't quite expect, such as double-counting figures, or adding multiple names to a single field.

These weren't mistakes as such, but they would cause errors when we fed the data to third-party systems, which meant a referral to a human reviewer and a delay for the customer.

We've invested a lot in removing less useful questions and reframing those that remain so they're clearer and more jargon-free, as it should be obvious what we're actually asking for. Fewer data quality issues means smoother processing for everyone.

We're asking for far fewer income documents

Previously, if we couldn't automatically verify someone's income, we'd have to ask them for documents, such as payslips, bank statements, HMRC forms. 

It works, but it's not a great experience. Many customers don't think of us as a finance company first, so being asked to dig out sensitive financial paperwork can feel jarring.

We've made two significant changes here. 

First, we changed how we looked at household income, so that we can more easily verify customers whose pay goes into a joint account. 

Second, we've upgraded to more advanced income verification tools, which give us a direct read on what someone earns, so we’re no longer relying on higher-level data.

When we launched Sunsave Plus in early 2024, we were asking roughly 60% of customers for income documents. Today it's around 5%.

We've found a smarter way to verify home ownership

To offer Sunsave Plus, we need a homeowner on the application, as they're the only ones with legal authority to let us install solar at their home. 

We verify homeownership using HM Land Registry, but this isn't always up to date, particularly if someone has bought their home recently. 

We’ve seen cases where records were as much as two years out of date after COVID. It's come down a lot since then, but it's still running at three to six months today – which is a real problem, because a lot of our customers have recently moved in.

We've solved this by updating our lending policy to accept other indications of homeownership, without having to rely solely on HM Land Registry.

It's a pragmatic fix that removes a blocker for a meaningful number of customers.

We're making our solar finance faster and fairer

We're lending to a greater proportion of the people who apply, making decisions faster, and asking for far less from customers along the way.

Solar should be accessible to as many UK homes as possible, and a fair, efficient underwriting process is one of the most tangible ways we can support that.

And we’re not done yet. We'll keep improving our models and adopting better tools as they become available.

Robin Mabley

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How we've made our underwriting process better for customers