Move over wind farms: why some argue cutting costs is the best way to cut carbon
"I'm an early adopter of new technology," says Gavin Tait, a 69-year-old from Glasgow, with a hint of pride.
"I'm an early adopter of new technology," says Gavin Tait, a 69-year-old from Glasgow, with a hint of pride.
So when he received a lump sum on retirement a decade or so ago, he invested in renewable energy: solar panels on the roof, a home battery and a heat pump. "It seemed like a no-brainer," he recalls. "I could save money and help the environment - why wouldn't I?"
At first, it worked. His well-insulated home stayed warm and his energy bills fell. But over the past couple of winters, things began to change. "I noticed my electricity bills were going through the roof," he says.
This winter, he and his wife switched it off and went back to their gas boiler, which they had kept as a backup.
Gavin - who wrote in to BBC Your Voice about his experiences - says he knows what the problem was. At best gas delivers nearly one unit of heat for each unit of energy put in; his heat pump can deliver up to three or four units of heat for every unit of power. But as heat pumps run on electricity, he is now paying around 27p per kilowatt-hour, compared with less than 6p for gas that powers a boiler - more than four times as much.
"It's simple," he says. "Economically, it just doesn't stack up."
His experience is not unusual. A survey of 1,000 heat pump owners last summer, carried out by Censuswide for Ecotricity, found two-thirds said their homes were more expensive to heat than before.
For critics of government policy, stories like Gavin's point to a deeper problem.
Heating and transport account for over 40% of the UK's emissions but they say that progress on replacing gas boilers and petrol cars is lagging well behind targets because ministers have got the wrong focus.
In their view, the government is obsessed with cleaning up electricity generation, even though it accounts for a far smaller total of our emissions - around 10%. So that obsession is pushing up the price of electricity and making it more expensive for people to switch to a heat pump or electric vehicle.
The issue has taken on new urgency as conflict in the Middle East pushes up oil and gas prices, raising fears that high energy costs could persist.
The government insists that focusing on renewables will ultimately deliver greater energy security by reducing reliance on imported gas, lowering emissions and - crucially - cutting bills.
Are they right? Or by prioritising cleaner electricity while progress on heating and transport lags behind, is the government chasing the wrong targets?
The issue is that while generating renewable electricity can be cheap, the system needed to deliver it is not. When I ask Sir Dieter Helm, professor of economic policy at Oxford University, for his definitive answer on the cost of renewables, he laughs.
"It all depends what you choose to measure," he says. Sir Dieter says focusing only on the cost of generating electricity misses a larger issue: the cost of the system as a whole.
Electricity has to be available all the time - not just when the wind is blowing or the sun is shining. That means back-up generation, additional capacity and a more extensive network.
Sir Dieter gives me a simplified example. The UK's peak electricity demand is around 45 gigawatts (GW), he says. In the past, this could be met with roughly 60GW of capacity from coal, gas and nuclear power stations.
As the system shifts towards renewables, far more capacity is needed - not just wind and solar, but back-up for when they are not producing. In Sir Dieter's estimate, the UK is moving towards something closer to 120GW. At the same time, the grid must also be expanded to carry electricity from offshore wind farms to where it is needed.
The exact figures are debated, but the direction is clear: partly because of renewables, the system is becoming larger, more complex and more expensive. Some of those costs are already showing up in bills. Expanding the grid - building new pylons and power lines - is pushing up network charges.
There are also "balancing costs", including payments to wind farms to switch off when the system cannot absorb all the electricity they produce. And until recently, a subsidy scheme accounted for around 10% of the average household bill.
There is another issue. The UK is richest in one of the more expensive renewable resources - offshore wind.
Solar power has seen dramatic cost reductions thanks to mass production. But Britain's often dull skies - especially in winter, when demand is highest - limit how far it can carry the system.
Offshore wind is more dependable but it involves large, site-specific engineering projects that cannot be replicated in the same way, and so have not seen the same sustained falls in cost. At the same time, rising prices for materials such as steel and rare earths - along with higher interest rates - have pushed costs up further.
On paper, the UK has made significant progress on going green — the nation's emissions are down by around 50% since 1990. But that does not necessarily mean the UK's overall global footprint has fallen by that much.
Many of the goods that were once produced and then used in Britain are now being made overseas and then imported here, and often that production is happening in countries with a higher carbon footprint.
China, for example, still relies on coal for more than half of its energy, meaning emissions simply have shifted abroad rather than been reduced altogether.
This is a point made by leading climate scientists including Prof Kevin Anderson of Manchester University, who argues the 50% figure "excludes international aviation and shipping and our imports and exports".
He adds: "If you include those, which of course the climate includes, then the reduction's about 20% since 1990." The government says it follows United Nations guidelines on emissions reporting.
At the same time, the higher system costs do not just show up in household bills - they ripple through the wider economy. UK households face some of the highest electricity bills in Europe. For businesses, the picture is even starker.
While the cost of renewables plays a part, the principal driver for this is, ironically, gas itself. The UK energy mix at any one moment usually includes plenty of renewables, but some gas is still frequently still needed. The way the market works, generators bid to supply power in half-hour blocks, with the cheapest bid accepted first. But all successful bidders end up being paid the price of the most expensive source needed to meet demand.
In practice, that source is usually gas. So, even when much of the electricity is generated from renewables, which are cheap to produce once you get past the hefty set-up costs, it is often gas-fired power stations that set the price - and therefore what everyone pays.
