Lotus Energy

24/08/2026

Another Heat Geek install in an unsuitable home, when will we learn?

15/08/2026

It might seem an unlikely way to stop overheating, but many owners have found the tech a lifeline in hot weather

14/08/2026

12/08/2026

A heat pump can cost more to run than the gas boiler it replaced.

That is not an argument against heat pumps. It is an argument against badly designed ones.

The maths is simple enough. A good gas boiler makes heat at about 8.37p per kWh round here. Electricity is 26.42p. So a heat pump has to produce at least 3.2 units of heat for every unit of electricity it uses, just to break even with the boiler you took out.

Design it properly and you are at 4 or better. On a typical Surrey home that is about £315 a year less than the gas boiler.

Get it wrong and you land at 2.5, and you are paying £160 a year more than you were.

Same house. Same heat pump. The difference is flow temperature, emitter sizing, controls and commissioning. None of which shows up on a quote unless you know to ask.

Complaints about heat pump installs went up roughly 24 fold between 2021 and 2024. The most common fault is an oversized unit short cycling. The second is flow temperatures left at 55 to 60 degrees when they should be 35 to 45, which on its own costs about 40% on running costs.

The unit in the first photo is a Vaillant aroTHERM plus. It sits on anti vibration feet rather than straight on the slabs, and the pipework is insulated properly. Small things. They are the difference between a system that runs quietly at the efficiency it was designed for and one that does not.

Every job we do gets a room by room heat loss survey, and we will show you the design flow temperature we are working to. If an installer will not show you theirs, that tells you something.

Full breakdown with all the figures on the blog. Link in bio.

11/08/2026

New on the blog, and it is the honest version rather than the sales version.

A heat pump can cost more to run than the gas boiler it replaced. On a typical Surrey home using 12,000 kWh of heat a year:

Designed properly, at a SCOP of 4.0, it costs about £793 a year. That is roughly £315 less than the gas boiler.

Designed badly, at 2.5, it costs about £1,268. That is £160 a year MORE than the boiler it replaced.

Same house, same heat pump. The difference is flow temperature, emitter sizing, controls and commissioning.

The post has the full working: current Ofgem prices, what the heat pump tariffs actually do to the numbers, and where the Boiler Upgrade Scheme stands, including the £9,000 for off gas grid oil replacements that runs out in March 2027.

https://www.lotusenergy.uk/heat-pump-running-costs-surrey-2026

13/04/2026

24/03/2026

5 heat pumps fitted this year (3 boilers too, but we don’t talk about that), not only saving tonnes of carbon, but saving clients money too. Thanks to legislation announced in the last Budget, a lot of the levies on electric prices have been moved to general taxation, meaning the spark gap is reducing, making heat pumps cheaper to run that gas boilers in most homes. With the algorithm, install costs are coming down thanks to AI aided design, plus you get a 5 YEAR efficiency guarantee .uk

06/01/2026

Just had my new batteries and inverter delivered, an ‘Earth friendly’ alternative to Lithium batteries. My first foray into the world of home energy storage, but would like to eventually offer it alongside heat pumps, under my own MCS. But let’s see how much admin/training/red tape is involved first.

31/12/2025

So, the results are in on the 5 bed, 280m2 Victorian house, and the results may be surprising. Long story short, the heat loss is around 12.5kW, or just under 45w/2. This house has solid uninsulated 9” brickwork, solid uninsulated floors, uninsulated tile clad timber framed 2nd floor with lathe and plaster internal walls, and a leaky front door. Fabric upgrades are limited to loft insulation where possible, and double glazed windows. The Vitocal 150-A is maintaining 21-22° internal temperature, at -2.4° outside temp (both figures 1° above design), however the flow temp is around 10° below design, proving how far out the whole methodology is. The backup heater did come on in the middle of the night, when the desired indoor temp jumped from 20° to 23° (to take advantage of the off-peak tariff), but only used 1.6kWh of electricity, about 11p worth at that time of day. Sticking to CIBSE design guidelines on this job would have increased the install cost by around £15k, making it entirely untenable and meaning the gas boiler would have remained in use. By looking at actual gas consumption at design conditions, we were able to specify correctly, save around £15k from the install cost, reduce CO2 emissions by around 6 tonnes per year, plus NOT fit loads of extraneous components, each with their own embedded carbon. This strengthens the case for using monitoring and measuring existing heat sources, rather than traditional heat loss survey methods, especially on older properties.

19/12/2025

Very happy with how this panned out. A Victorian farmhouse with solid walls, a CIBSE estimated heat loss of 24kW, but the gas usage didn’t stack up. Smart meter data and checking the boiler efficiency, as well as rules on thumb on annual gas usage, both suggested 11kW total heat loss. By using Historic England data on period properties, as well as being confident enough to slash ACH values right down, resulted in getting the survey heat loss to 13kW, just enough for the biggest Vitocal 150-A. Coupled with a cylinder, and 15 new Charleston column radiators, piped direct with no buffer, it’s working very nicely and settled on a curve of 0.9, which is approx a 47° design flow temperature.