1. Monbiot argues that "either solar photovoltaic (PV) power in the United Kingdom is, as (Leggett) claims, a cheap, efficient technology, or it isn't. If it is, why should we be subsidising it to the tune of 41p per kilowatt hour? If it needs this subsidy, it is neither cheap nor efficient. If it doesn't need it, the feed-in tariffs are even more of a swindle than I thought."

This view takes a snapshot in time that is a flawed basis for analysis because it ignores both the past and the future, in terms of cost, plus the strategic context of the discussion. I don't claim PV is "cheap" today – I never have. PV is on a descending cost trajectory because economies of scale are at work in both manufacturing and installation, and costs and prices of conventional electricity are rising fast. The feed-in tariff is a market-building mechanism. It is designed to create sufficient demand for PV systems to trigger two benefits: first, falling cost and price of solar electricity, and second, growth of a proper UK-based solar PV industry that can compete with the fast-growing industries in Germany, China, the US, Japan and many other countries. More than 40 governments now have feed-in tariffs, and it is clear that many people believe them to be the best way to make grow renewables markets fast.

2. Monbiot bets me £100 that my prediction that solar PV electricity in homes will be no more pricey in 2013 than conventional electricity will be wrong.

I accept Monbiot's bet. But I have a proviso: that the winner donates the £100 to the charity SolarAid, set up by my company, for the training and equipping of solar PV lighting entrepreneurs in Africa.

This seems appropriate because of another sad aspect of Monbiot's assault on PV. He does not mention the strategic importance of providing channels of distribution and credit for mobilising solar PV in the developing world, where solar PV electricity is already economic in competition with kerosene and other alternatives. As even the World Bank has admitted, solar PV is a better bet than conventional power plants for the hundreds of millions of developing-world households currently without electricity.

If I lose the bet on timing of UK grid parity, it would only be by a few years at most, and by 2013 I am confident that people will be able to see the writing on the wall with respect to grid parity. And herein lies my return bet with Monbiot. I bet that if we are near or at grid parity by 2013, that we won't see a column of his admitting to how wrong he was. If he does, I'd gladly donate another £100 to SolarAid.

3. Monbiot suggests that if I "really believed" my sales pitch, I would be calling for the feed-in tariff for new installations to be scrapped in 2013, as it would then be redundant: "He can't have it both ways: defending the tariff while suggesting that the tariff won't be necessary."

I have never suggested that the "tariff won't be necessary." The government does not share my view of when grid parity will be delivered, but nor do they believe as Monbiot appears to that new industries and new installer capacity can just be turned on overnight.

By 2013, just three short years from now, the UK will still be endeavouring to build a domestic PV industry that can compete globally. To do that we will need a strong domestic market. To build that we will need a continuing market-enablement regime. The feed-in tariffs can and will be lower by then, but we will still need them. Otherwise, with a low-growth domestic market in an explosively growing global market, we will be importing almost all the solar technology we useand we will have further undermined our chances of energy independence down the track.

4. Monbiot asserts: "Every pound spent on PV is a pound not spent on a more effective technology."

This is another use of the flawed snapshot argument devoid of strategic considerations. If we were to use only the current price of energy technologies as a yardstick, and discount all trends and strategic considerations, we would allocate all our money to energy efficiency, where we get the quickest paybacks and carbon "bang for the buck." But this not an either-or: we can't solve all our energy problems with energy efficiency. We will need plenty of new generation to replace aging coal and nuclear plants, and this will have to mean a range of generation by renewables, alongside as much gas as Vladimir Putin and others overseas will allow us. We would be crazy just to go for the technologies that happen to be the cheapest in March 2010, and it is extraordinary that an advocate of expensive nuclear like Monbiot can argue this.

5. Monbiot says of the German feed-in tariff: "The realisation in Germany, after 10 years of minimal returns, that they have been getting shockingly bad value for money from their scheme coincides with the launching of the same fiasco in the UK".

It is untrue to suggest that the returns are minimal. Consider just taxation. In 2008, the German government gained almost €3bn from the direct and indirect taxation of German solar power companies and their employees. In the same year, feed-in tariff investments amounted to about €2bn.

6. Monbiot questions the jobs the German feed-in tariff has created. He says: "Leggett goes on to claim, again without attribution, that the Germans have "created over 50,000 jobs in solar PV alone."

The 50,000 German employees are counted by the Federal Solar Industry Association. Monbiot's questioning of even this statistic introduces another relevant issue. I have invited him in to Solarcentury several times to discuss the detail of our story and have a go at calibrating numbers ahead of any epistolary exchanges. I have had no success. He seems to prefer unrooted conflict from afar.

7. Monbiot also questions the location of jobs created. He says: "The electricity users who have to pay for the tariff would be rather put out to discover that the jobs the government says it will create are actually on the other side of the world."

How many mistakes can you make in one article? The Federal Solar Industry Association count over 100 factories in Germany in the industry built to date by the feed-in tariffs. Then there are all the installer companies.

Certainly modules are also imported from China and Japan as well. The global PV market is one of the fastest growing markets in the world (87% in 2008). That is why UK plc needs to be a part of it.

Feed-in tariffs in the UK will lead to many jobs in the UK. Solar companies estimate that around 100,000 new jobs could be created in the UK by 2020. And they will be skilled and fulfilling jobs.

8. Monbiot persists with the argument from his first article: that the British poor will subsidise the solar roofs of the middle class. He says: "Their bills will rise just like everyone else's to pay for a scheme which will mostly benefit the middle classes. This is why it is deeply regressive."

First, it is necessary to be clear about the numbers and the likely impact on average household bills as a result of this scheme. The average yearly cost of the feed-in tariff scheme to household levy payers is projected to be £8.50 per year to 2030. The average annual household levy in 2013 when tariff rates are all up for review is likely to be £3. And those are the costs for all technologies not just solar PV. So the question is whether an average household levy of just £8.50 per year makes the feed-in tariff scheme regressive or not? Furthermore, the government has already committed to make the scheme revenue natural by offering loans whereby households can borrow the capital cost of energy efficiency and renewable technologies and repay them over time using the money saved as a result of installation.

And if PV was so regressive, how come housing associations are so keen on PV as a tool for addressing fuel poverty?

9. Lastly, Monbiot accuses me of ignoring a "killer fact". He says: "Feed-in tariffs cannot reduce our carbon emissions by 1g while the UK remains within the European emissions trading scheme (ETS).

Monbiot and I might find things to agree on, when it comes to scope for nonsense in the European emission trading scheme, as it stands. But climate policymaking requires many tools in the toolkit, and there is no reason to throw feed-in tariffs out just because politicians have historically granted heavy industry emissions allocations that are too high to deliver an effective carbon price. Monbiot's "killer fact" taken to its logical conclusion would mean no support for any low or zero carbon technology outside the EU ETS.

• Jeremy Leggett is founder and chairman of Solarcentury, the UK's largest solar solutions company.