I went to visit a neighbour recently to help him think through the cost/benefit of switching his gas boiler to a heat pump. He had recently had solar panels and a large battery installed, but had unusually large daytime electricity usage for his son’s home-based business. Would a heat pump work in his house – and would it actually save money? Would adding more batteries help, and what if he switched to a cheap overnight tariff?

There are a lot of variables to take account of when trying to work out estimated running costs and returns from home green technology, and most installers (understandably) focus on their own part of the picture: solar panels, energy tariffs, heat pumps, or insulation.

The spreadsheet I started to make quickly got out of hand, so I’ve been building a little app to quickly compare the current setup and energy cost of your home with a rough estimate how those might change with various upgrades (solar, heat pump, battery, insulation) or switches (tariff). It incorporates the main variables and some rules of thumb to come up with round numbers to give you an idea of how the bottom line running costs might be influenced by different upgrades, and what the payback periods might be for a combination of green technology investments.

You can try it out without logging in or sharing any details with me or installers by plugging in a handful of details of your current home here:

There’s an in-depth mode too if you want to dive deeper (contact me, details on the About page), but really this is more about quick rough estimates in any case. There are tools like the Household Co-Benefit Explorer by Open Energy Monitor built by people much more expert than me that help to calculate these things if you have the time and data – do check them out too.

All comments, corrections and suggestions welcome.