BUT if you need less energy, then you need LESS to fill the gap too.
Irrelevant. We'd still need energy. Conservation is a good idea that I wholly support. The problem is that one can only conserve so much before it starts to affect their standard of living. This comes through either increased expense in the form of energy efficient devices and materials, an expense that is not offset by the energy saved, or through an inconvenience.
Or adapt you standard of living so they can survive even if you switch to more wind and solar. If at night all people start using lower-power LED instead of incandescent light-bulbs, the "gap" that the utilities need to compensate is smaller.
No, that "gap" does not get smaller. The utilities have to produce power based on an consistent "base" usage and on the peaks. For residences the utilities charge consumers based on their average costs, industrial/commercial users may be offered discounts on certain times of day for power usage to address those peaks. The "gap" between the base and peak has to be made up with expensive peak power. The larger that gap gets the more expensive electricity becomes.
When adding solar as a power source there's an added complexity, the utility doesn't just have to compensate for the power consumed by their customers but also by the power they produce. It makes the "gap" between base power and peak power a greater percentage of the total. Energy efficient lighting reduces the total power consumed but does little to affect that "gap".
An interesting thing about CFL and LED lighting, they have power supplies in them that are very adaptive to the power they are supplied. They do this so that they can be used in a number of places with different power and still produce a consistent light output. The same power supply can be used for places wired for voltages from 110, 120, 208, 220, 250 and anywhere in between. Also they don't care on if it's 50 or 60 hertz. Old incandescent lights are somewhat similar in that respect, the voltage has to be within a tighter range, they can't vary from 240 volts to 110 volts but they will give pretty much the same light on 110 volts as they do on 130 volts.
I go through that explanation of lighting to point out how badly utilities hate these new lights. It's not because they affect profits from reduced consumption by customers, they will always adjust their rates accordingly. One problem is that these new bulbs add reactance, a load that is either inductive or capacitive. Reactance messes with the generators and need to be compensated for to keep them running. Incandescent bulbs are almost purely resistive, utilities like resistive loads. Another problem is that they consume the same amount of power regardless of voltage. If there is a problem at the utility a common result is a voltage drop. With incandescent lights a voltage drop means reduced power consumed. With the fancy new bulbs a voltage drop means the same, or more, power is consumed. That is a problem with the utility, if power used does not reduce with voltage then a runaway condition can happen. Instead of the lights dimming a bit and coming back up the lights keep trying to stay on at the same brightness, the current consumed goes up and up until wires get hot and fuses start to trip.
These incandescent light alternatives are adding on to an already complex system. Solar and wind make it more complex. The more complex the system the easier it is to break.
Indeed that's easier for us (we already have this possibility) than for you in the great plains (you probably will need to slowly start things like compressed-air energy storage, etc. or other such technologies)
Energy storage also adds to the complexity, and cost, of electricity. Solar and wind are already expensive, more expensive than even the cheapest peak power we have. No one uses this stuff because it is cheap. The only reason we use it all is because some legislators thought it was "green" when it is not. We burn more natural gas to make up for the times when the wind does not blow or the sun does not shine than if we had just burned that natural gas in an efficient boiler.
Pumped hydro only works because the losses in the system are made up with rain. With compressed gas, weights on ropes, whatever, the power out is always going to cost more than the power in because of the losses. Solar is already mind blowing expensive, adding compressed air storage is only going to make it worse. Wind is approaching the costs of peak power sources right now so a lot of utilities like it since it makes for a nice PR show when greenies and politicians show up. Wind power also has an "off" switch. If the grid becomes unstable because the wind is adding too much power they can feather the blades on the turbines and have them stop spinning. Residential solar does not allow for that, they have to take that power.
Another cute fact I heard of wind turbines is that they need to be spun up to speed so that they can catch the wind. There's a motor in those turbines to get them spinning. Theoretically I assume that windmills could be used as a sink of power as much as a source. If they need to shed some excess power the utility could just spin some windmills. I don't know if they do that but I would not be surprised to find out that they do.
I understand you're dislike of coal power, I share it. The problem is that for much of the USA, and much of the world, we don't have the luxury of mountains and water for cheap pumped hydro. That makes expensive wind and solar power even more expensive. I see the solution in nuclear power.