If the utilities didn't get any subsidies from the government then it wouldn't be an issue. Electricity costs would increase as demand shifts out, the excess surplus for the power company would allow them to invest in more infrastructure. The big customers would contribute more to the new infra because they buy more electricity.
However if utility companies do get subsidies to spend on infra, then it doesn't matter how much electricity a person buys, the money is coming from taxes separately from how much electricity anyone is buying. This would allow large consumers to take advantage of tax payers to build the infra to shift out the supply, which mostly benefits the large consumers.
The TLDR is that this is a known drawback of utility monopolies and subsidies, and if you took those away it wouldn't matter how much electricity anyone was using, it would all sort itself out with prices.
I'm not sure you can say a utility company prices are better set by the free market. Even outside government enforced monopolies, you can't exactly pick and choose a utility, or hook multiple up
I specifically said that you needed to get rid of monopolies and subsidies for prices to work.
Most places are not set up for that, and giving a power company a monopoly is a necessary evil. That's not a solution without a tradeoff though. When you have a monopoly, the consumers need to collectively negotiate prices. Part of that negotiation can lead to other forms of rent-seeking in the form of subsidies, or whatever else. It's just trading problems for problems.
What might a better solution look like? Having municipalities own the last mile, and take ownership of the grid might eliminate the need for energy monopolies. Multiple energy suppliers could compete, and the grid would be maintained through contractors. The contractors hired to tend to the lines and conduits wouldn't be in the power business, they would be in the plumbing and wiring business. There is a state monopoly on the grid infrastructure, the same way there is a state monopoly on roads. There's no government truck or car monopoly even though that's what uses the roads.
There has to be some sort of regulation --- ~50% of the cost of electricity is for transmission/line maintenance --- though I would argue that the traditional electric co-operatives are the best option for rural areas.
However if utility companies do get subsidies to spend on infra, then it doesn't matter how much electricity a person buys, the money is coming from taxes separately from how much electricity anyone is buying. This would allow large consumers to take advantage of tax payers to build the infra to shift out the supply, which mostly benefits the large consumers.
The TLDR is that this is a known drawback of utility monopolies and subsidies, and if you took those away it wouldn't matter how much electricity anyone was using, it would all sort itself out with prices.