From Oil Boiler to Net-Zero: Our Journey

My wife and I wanted to make our house warmer — and kinder to both the planet and our wallet.

For me, this was something of a homecoming. I did a doctorate on solar cells 40 years ago, and now, recently retired from engineering and business, I finally had the opportunity to put theory into practice: designing and building a truly net-zero home powered solely by green electricity.

Giving back – profitably

I wanted to give back to the planet. And honestly, I expected to pay for that privilege — a kind of ethical surcharge. But, as for many pensioners, avoiding paying over the odds for things is a bit of a hobby. So I wondered: could we do the right thing and still come out ahead?

Heat pumps have a mixed reputation. But with careful planning and the right system design, it looked like we might have our cake and eat it.

So, I built a few software tools to help optimise a design. The project began when we moved to a 1960s detached house in West Berkshire — oil boiler, a few aging solar thermal panels, and not much else. No fancy insulation. No recent upgrades.

Despite the sceptics, the deniers, and the “it’ll never pay off” crowd, our renewable-powered house turns a profit. The system performs almost exactly as predicted. In fact, it delivers returns that rival — and in some ways outperform — the stock market.

The results

  • NO energy bills: Octopus Energy pay us
  • nearly 14 MWh electricity generated in our first year
  • 60% exported to the grid
  • projected £16,000 better off over the lifetime of the system
  • no CO2
  • no air pollution

Why renewable planning is hard

If I sound a bit smug, it’s because we may have addressed the biggest and most common issue with home energy projects: figuring out how the complete system will perform before spending a penny.

When it comes to ridding ourselves of CO2, there are many alternative energy components to choose from: insulation, solar thermal, solar PV, wind generator, batteries and heat pumps all might achieve this.

A blend of these components is often required to obtain optimal energy efficiency and financial performance. But most installers make projections that ignore components they don’t sell or know. Energy modelling can be a minefield of guesswork, oversimplification, or opaque spreadsheet voodoo.

Reality is complicated:

  • heat pump efficiency depends on temperature swings by time of day, the weather, hot water and room temperature;
  • solar panel output varies with weather, temperature, and time;
  • tariffs fluctuate depending on time of day and import/export;
  • batteries wear out with use;
  • solar inverters clip excess energy;
  • distribution networks (DNOs) cap how much you can export.

All of these interact. And unless you’re prepared to take a hit by hiring expensive consultants, it’s nearly impossible to model them all together reliably.

So I wrote some planning tools

I wrote software to simulate different renewable energy setups: solar, batteries, heat pumps, thermal storage, insulation strategies, and more — all working together as an integrated system.

This site is about that planning journey — and the lessons I learned along the way.

For the few months it took an old dog of a retiree to write these tools, we now have a system that leaves us over £30k1 better off compared to the oil boiler we left behind.

I hope to encourage more home owners to take a similar plunge … even if it is at the risk of driving down solar export prices.

So if any of this is relevant, see my blogs, play with the tools and tell me what you think.

Jonathan

What’s in it for you?

If you’re thinking about upgrading your home energy system — or just curious about how to do it well — you’ll find:

  • Blog posts sharing insights from each phase of our journey
  • Free planning tools to help you evaluate your own options
  • Hard-won lessons from the front lines of DIY energy optimisation

Join the conversation

This is a journey, and I’d love to hear your thoughts along the way.

  • Have you done something similar?
  • Are you facing hurdles in your own energy upgrade?
  • Want help making sense of the tech, tariffs or trade-offs?

Drop a comment. Share your story. Let’s learn from each other.

  1. If only forecasts are so easy in practice: £30k was the figure when we started. Since then the price of oil has fallen and the figure is now £16k … and still a switch to net-zero that costs less than nothing. ↩︎