There's nothing more irritating than the fashion for converting all our opinions into "isms". You know the kind of thing – "smokeism"for objecting to smokers. Or "lookism", the new name for discrimination against people with less than perfect appearances. And how about "beefism"? Apparently, it describes the views of militant vegetarians. Aarrgh!

But there's one "ism" which I reckon more than justifies its place in the lexicon. Ageism is the last socially acceptable prejudice in our society – and it is rampant. Reader Rose Frain is very cross about an article in 'The Independent' last Thursday, which described the artist David Hockney as a "pensioner" even though the piece had nothing to do with pensions – or the elderly. "Sloppy and demeaning language," she calls it, and goes on: "This is about as accurate as referring to everybody under 60 as 'worker'. It is extremely condescending and unworthy of 'The Independent'. How dare you refer to anyone, let alone a distinguished artist, as a pensioner? I am very angry." Don't we have a policy, she asks.

Actually, Ms Frain, not even society as a whole has a policy. Astonishing as it may seem, while we have laws covering race, gender, sexuality and faith, there is nothing to prevent discrimination against older people, except in the workplace. And campaigners point out that careless use of language, such as "pensioners", "wrinklies" and "twirlies", is just the tip of an iceberg where older people are regarded as second-class citizens on a whole range of counts, from getting NHS treatment to insurance policies. "For some older people, it's still a bit the old 'no blacks or Irish' attitudes of the 1950s," said one.

As for stereotyping, we in the media are as guilty as the rest. Anna Ford, Nick Ross, Moira Stuart and Peter Sissons are among many top BBC figures who have complained about ageism in the corporation. And it's hard to disagree with the Lib Dem MP Lembit Opik when he says his leader Ming Campbell was "driven out of office by the media's obsession with his age". The US media are now giving the same treatment to John McCain – recently described by David Letterman as a "Wal-Mart greeter".

Now you might argue that David Hockney can look after himself, as can other famous members of the bus pass generation, such as 61-year-old Elton John, 64-year-old Mick Jagger and 65-year-old Paul McCartney. Helen Mirren continues to win "sexiest woman" polls at 62. But their PR machines and Botox clinics have to work ever harder. And what about the rest of the over-60s who don't happen to be celebrities and who will soon outnumber the under-25s?

Don't hold out your hopes for change. My spies at Westminster tell me that ministers are busy watering down plans to curb age discrimination, due in this autumn's Equality Bill. Apparently it's not a sexy enough issue. Meanwhile, how many more gags about Senator McCain, dementia and Zimmer frames can you take?

Message Board: Does power generation begin at home?

Our front-page story last week showed that houses can harness energy from the sun and wind. The prospect led to a heated discussion at ios.typepad.com

Andrew

Grants to the public to install such technologies would boost the industry, reduce manufacturing costs as the market expands, and reduce the requirement for costly new power plants. Simple, really!

Martin

The cost of decommissioning nuclear power stations would be £73bn, which is roughly £3,000 for every household. That would go a long way towards renewable energy installations for all of us.

alan

The right to sell back to the grid makes more sense than subsidies because an empty property can generate power for the neighbourhood; a subsidy generates a tax increase for the neighbours.

Marsha

I live in Las Vegas, Nevada USA – the most sunshine in the US – and we cannot provide that kind of energy through solar power. Besides, isn't the real issue how to store the energy?

Val

Micro-energy generation reduces dependence on major installations that can be affected by external factors (other governments' policies and prices) and are vulnerable to terrorist attack and to faults.

rose

We have a Government that likes to dictate to us, eg banning smoking. What they should do now is dictate green building methods – we need a dose of liberal fascism.

Burkhard

I studied in the UK for one year and was shocked by the low level of recycling. This situation could easily be reversed if the Government would provide the right incentives. The same applies to energy.

kate

As a green-minded mum on a low income, it has become increasingly difficult to turn to micro-generation. It seems that you have to be wealthy to be able to make the greenest choices in life.