In fact, you make the exact same mistakes they do, and more, which are critical ones.
Personal Capital's Retirement Planner is quite a bit different too. For one, it's a Monte Carlo simulator. Two, it assumes your retirement income will remain constant for your entire retirement. Third, to use their calculator they make you sign up, link your accounts and endure the harassment of their financial advisors.
There's a lot of details that are required for increasingly better projections, and sometimes people taking a glance at what your software has to offer might not necessarily have time during their lunch hour or on the weekends to fill everything out.
Yes, Personal Capital targets sub-HNWIs, but realize they run a business, and if they're targeting you, it's also a sign you're probably doing something right.
So if you need a public domain based approach to retirement calculations, you might be able to follow what they are doing.
How does your strategy differ from the many ERN evaluates?
The thing that's most different about my strategy is that it doesn't have a 'memory' of what your past retirement income was. Put simply, you retire every 3 months. A lot of folks get nervous when I say this but in practice, this is in fact how most people behave.
For example, consider the case of someone who unfortunately retired just before the COVID crash. Strategies that have a 'memory' intrinsically offer some assurance that you'll probably weather the downturn without decreasing your lifestyle very much. In practice, most folks will 'start over' their retirement just to be safe and reset the memory of their prior payments. In my opinion, if you're not going to trust the assurances of a given strategy then what good is it?
Another thing that sets my strategy apart is that it focuses on capital depletion. Most strategies don't have any sort of annuity component and this typically resorts in a binary outcome near the end of the investment horizon -- you're either filthy rich or you went bankrupt years ago (both of these are bad outcomes for me). My strategy is constantly readjusting itself so that you exhaust your savings around 100 years old (or whatever age you set the formula to). This results in better overall effective utilization of savings.
I could go on but those are the two biggest things.
I have no intention of burning most of my investments away when I can instead, over a lifetime, teach my children how to manage their resources and insulate them from concerns most others toil away at.
I'd instead rather spend as a little as possible.