Solar vs Investing – Which Actually Makes You More Money?
- jontracey4
- 6 hours ago
- 3 min read
One of the most common comments I receive whenever I post about solar is:
“You haven’t factored in the opportunity cost.”
And it’s a fair point.
If you spend £20,000 on a solar and battery system, that same money could have been invested instead. Over time, that investment might grow significantly, so how do you know whether solar was really the better financial decision?
Rather than arguing opinions in the comments section, I decided to build something to actually test it properly.
I’ve now created a fully interactive Solar vs Investment Calculator, which compares two different approaches side by side using real financial modelling.
👉 Try the calculator here:https://www.jonathantracey.com/solarvsinvestments
👉 Watch the full video here:https://youtu.be/trkqIP9mM1g
The Core Question
The calculator compares two scenarios:
1. Investing the Money
In this scenario, you keep your £20,000 invested in an ISA or investment account and use that pot to pay your energy bills over time.
The model factors in:
Investment growth
Energy bill inflation
Monthly bill payments
Compounding returns
This is important because energy bills do not stay flat forever. Even modest annual increases can have a huge impact over 10, 15, or 25 years.
2. Buying Solar Instead
In the second scenario, the £20,000 is used to install solar and battery storage designed to significantly reduce or offset household energy bills.
Instead of paying those bills each month, the savings are invested into an ISA.
The calculator also accounts for:
Solar panel degradation
Battery degradation
Maintenance costs
Export rate changes over time
Long-term inflation
This creates a much more realistic comparison than the simple “payback period” figures often quoted online.
Why Payback Period Can Be Misleading
A lot of people focus purely on how quickly solar “pays for itself.”
The problem is that payback period only tells you how long it takes to recover the initial investment. It tells you nothing about what happens after that point.
For example:
What happens after 15 years?
What happens when energy prices rise?
What happens when your investment pot starts shrinking because it’s being used to pay bills?
That’s where the opportunity cost argument becomes much more complicated.
The calculator was designed specifically to explore those long-term effects.
The Results Can Be Surprising
One thing the tool highlights very clearly is that the answer depends heavily on your assumptions.
Small changes in:
Investment returns
Energy inflation
Solar degradation
Export rates
Maintenance costs
…can completely change the outcome over time.
That’s why I built the calculator with editable assumptions and scenario presets, allowing you to test conservative, base, and optimistic projections.
In some situations, investing may outperform solar.
In others, solar can end up significantly ahead, particularly if energy prices continue to rise and the savings are consistently reinvested.
A Financial Model – Not a Sales Pitch
One thing I want to make clear is that this tool is not designed to “prove” solar is always better.
It’s designed to model the financial trade-offs honestly.
There are plenty of videos online that present solar as a guaranteed win regardless of circumstances. Reality is more nuanced than that.
Your:
energy usage,
installation cost,
tariff structure,
export rates,
and investment performance
…all matter.
That’s why I wanted to create something data-driven rather than opinion-driven.
Try It Yourself
If you’re considering solar, investing, or simply want to understand the opportunity cost argument better, I’d encourage you to try the calculator yourself and experiment with different assumptions.
👉 Solar vs Investment Calculator:https://www.jonathantracey.com/solarvsinvestments
👉 Full YouTube Video:https://youtu.be/trkqIP9mM1g
I’d also be interested to hear your conclusions. Do you think investing wins long-term, or does reducing your energy bills create a stronger financial position over time?
Let me know in the comments on the video.
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