> is there anywhere in the world where adding wind and solar has led to lower electricity rates for ratepayers?
We do not have a spare universe without such additions to answer that question.
Hornsea Project 1 (1.2GW nameplate electricity generation from wind turbines in the North Sea) is running right now and is paid £140 per MWh under CfD terms. So, on a nice fresh day that's £168 000 per hour.
In 2019 you could say that's a ludicrous subsidy, the market price for electricity in the UK was about £50 per MWh so the government (and thus rate payers ultimately) are paying about 200% extra to subsidise this wind farm.
On the other hand, today (in January 2022) the market price is fluctuating closer to £200 per MWh due to gas prices and so £140 per MWh looks like a bargain.
[ The way Contracts for Difference works is you sell your electricity like everybody else, via some mix of long term and short term contracts, and the government tops up the difference between the market price and your "strike price" so that your income is always determined by your strike price not subject to changes in the market price. This also means if market prices are higher (as they often have been this past year) you pay the government back the difference so you still only get the income your strike price guaranteed. As a result the risk of not generating electricity stays with you, as does the risk of not selling your electricity for market prices but the government eats your risk that market prices are far lower than you expected while also gobbling up any windfall profits if market prices are far higher ]
Now, if Hornsea and similar wind farms don't exist, does the UK magically pay the same price £140 per MWh for that electricity even though gas is expensive and it has no other source of electricity ? Or do the prices go up even further? Maybe with no other choice the UK buys electricity for £300 per MWh or even £500 per MWh. The lights must stay on after all.
Also there are secondary effects. If you propose a new wind farm today, to start construction in 2024 and be online in 2030, you're not going to get a strike price of £140 per MWh because of course prices came down due to investment in the sector. But if there was no investment, why wouldn't you find wind farms in 2030 just as expensive as they were in 2015 ? And not only did prices come down, efficiency went up as suppliers gained experience and competed to offer better products, when Hornsea was proposed a 8MW turbine was best-in-class, Hornsea Project 2 intends up to 15MW turbines. The taller structure offers not only more peak power output, it also delivers higher capacity factor because high altitude winds are more constant.