I wanted to make our house kinder to the planet. This was to be a kind a kind of homecoming in that I did a doctorate into the physics of solar cells 40 years ago, but have paid little if any consideration to their environmental potential ever since.
Now, recently retired from engineering and business, an idea grew to make our house “net-zero”: powered solely by green electricity.
Giving back – profitably
A common presumption is that good evironmental practice must be to the detriment of self interest. I wanted to give back to the planet and expected to have to pay an ethical surcharge.
But as with many geeks, finding ways to avoid paying over the odds can become a bit of a hobby. I wondered: if I plan and design really carefully: might we actually come out ahead?
Heat pumps have a mixed reputation. But with careful planning and the right overall 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 common presumptions, our renewable-powered house turns a clear profit and has many other benefits. 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: in fact Octopus Energy pay us!
- No or very low car re-fuelling costs
- over 15 MWh electricity generated in our first year
- projected £16,000 better off over the lifetime of the system
- no CO2
- no air pollution
- comfort: more even temperature control compared to oil and gas heating
- immunity from most power cuts
Why renewable planning is hard
I sound a little smug because I feel that I have solved a common issue: knowing how our home will perform financially before investing.
When it comes to ridding the climate of CO2, there are many alternative energy components to choose between: insulation, solar thermal, solar PV, wind generator, batteries and heat pumps all might achieve this. However finding the most cost effective combinations of these is rarely discussed.
Combinations of renewable component are almost always required to optimise energy efficiency and obtain best financial performance. Installers do sometimes included financial projections when quoting. These can be questionable and, necessarily, they ignore components that come from other sources.
As a result, energy modelling can be a minefield of over simplification, simple guesswork or none at all.
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 these and other factors interact so, unless you’re prepared to take a hit by hiring expensive consultants, it’s nearly impossible to know their combined consequences 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 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.
- 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. ↩︎
