Heating News – Spring 2022

Energy crisis edition          Nearly free electricity and a free car!

Price caps for everyone.

Oil and gas now costs the energy suppliers so much that they all have to charge right up to the government price cap and there’s worse to come in October.

All offers therefor will settle at about the same level, 34.64p for electricity and 8.38p for gas with some sneaky increases on daily charges. Meanwhile energy prices continue upwards so future caps are very likely to be even higher. The new norm for total domestic energy costs looks more like £3,000 – £4,000 and that’s money that has been taxed. I make this point because any savings you can make are tax free. As usual the discussion for remedies largely revolves around PV solar panels and heat pumps, preferably both at once. We’ll have a look at turning down the thermostat too – what actually happens.

Solar panel returns – worth it?

The 1,000 cluster: By a strange coincidence 3 solar panels cost about £1.000 fitted. They will have a bit over 1,000W power rating and make over 1,000 kW.hrs in a year.  At 35p per kW.hr saved on your bills the 3 panels will make you £350 a year paying you back the £1,000 in 3 years.

So the deal goes a bit like this. You give me £1,000 and I’ll pay you back £350 a year for 3 years. Only then are you back where you started, which doesn’t sound so clever. However, by then prices could be up by 50%, at least, so you get £525 a year for the next 3 years (£1,575 ahead at this point) and then on the same basis another £2,360 over the next 3 years and so on. Crazy maths? Well electricity price rises have been steady at 8% a year and that was before the energy crisis so this all looks pretty real. Remember we are just looking at 3 panels for £1,000 here. Your real installation could be 6 times as big.

Not spending money on fuel bills puts money in your pocket but unlike other investments this is tax free and very like a pension scheme. On that basis PV panels make more sense for higher tax payers but still a good deal for … er … the rest of us.

New 240v solar panels

In the last issue I featured an Enphase Micro inverter with the comment that soon PV panels will have them built in as a matter of course. Since them Hanwha Q-Cells have launched a lovely all black, 385W panel (Q.Peak Duo BLK-G6+/AC 340-345 ACM) with the Enphase Inverter built in. So instead of high voltage wires going to one inverter box the panels all link up easily and deliver 240V directly to your mains circuit. The days of balancing strings, matching inverters etc are over. Now you can put panels in any shaped clusters that suit you. Enphase are having a major focus on Europe so we’ll hear much more from them in future especially when they use their superior electronics skills to launch a new electric car charger.

Turn down the thermostat – the real savings

‘The rate of loss of heat is proportional to the excess temperature of the surroundings’ So the warmer your house is relative to the outside the more energy you lose, and it’s a linear relationship. That makes the maths easy. If, say, your house is at 20c and its 5c outside the difference is 15c so a reduction of 1c on the thermostat reduces the heat loss by 6.66%. So, it’s the percentage reduction on the difference in temperatures. If it is 10c outside the difference will be 10c so a 1c reduction on the thermostat reduces the loss by 10%. Your bills corelate directly to this so whatever percentage is saved on the day is what comes off your energy bill, so the chances are you will be saving £200 or more over the year. One extra click down on the stat doubles the saving!

Solar PV annex building – the Powerhouse

Recently I have been pondering on the idea of an annex building with an integrated all solar roof. This involved juggling various layouts of panels, roof angles etc, so to prevent a whirling descent into madness I have constructed an Excel model that does all the calculations, right down to the finished size of the whole building. Happy to share if you are wrestling with the same ideas.

PV panels don’t like being roof integrated because they get too hot. The annex roof has an air gap under the panels so that air flowing upwards under them raises their efficiency. This slightly warmed air is directed into a void in the peak of the roof and then ducted down to your air source heat pump which runs very nicely on the warmer air giving a double whammy; better PV efficiency and better ASHP efficiency. In addition, the ASHP avoids the colder ground air and largely avoids costly defrosting cycles.  A similar concept is even easier to implement on a car port or garage.

The combination of an ASHP and the PV is a marriage made in heaven. Free power is turned into over 3 times more heat as all our small gains in efficiency are multiplied up by the COP of the ASHP. The Powerhouse makes electricity and heating and pretty much covers most domestic energy needs.

One attraction of the powerhouse is that it can be sited to point south unlike some houses which also suffer from shaded roofs, chimneys etc. Also, the local planning committee will tend to look more favourably on applications that involve innovation and ecologicalness.

What about batteries?

After the sun goes down batteries deliver free solar energy back to you; …… or do they? Actually, the batteries cost money to buy and they degrade with every cycle so there is effectively a charge to your pocket for each kilowatt.hour they store and you’d be shocked by how much. Ordinary lead acid batteries will charge you nearly 50p to recycle a kilowatt.hour, so more expensive than the mains. It gets better with lithium batteries with 20p a regular figure and 5.5p seems to be the limit. So, if you choose carefully the batteries will beat the mains on delivery cost. The Bimble Solar web site lists masses of batteries with their energy delivery costs so check it out before you buy.

Cheeky thought of the day. The Tesla power wall costs about £8,600 and stores 13.5kW.hrs and like all batteries it wears out in time and has to be replaced. However, the battery in your electric car is much better than that and if you are leasing the car you don’t care about degradation. So check out two way charging where you can get power out as well (V2H). The cost comparison is interesting. 4 Powerwalls would cost £34,400 but the batteries in a Nissan Leaf store more for the same money and they come with a free car thrown in as well! I admit it’s early days for this type of thinking; V2H chargers are expensive and not many cars support V2G or V2H but you might as well get ahead of the curve for your future energy strategy. At the moment you are probably looking at a Nissan Leaf and within a year a VW.

Late night power for car charging costs 7.5p/kW.hr with Octopus Go. What this all means is that two way charging with a battery makes your electricity cost 7.5p/kW.hr as opposed to 35p++ and that makes a leased electric car a viable consideration. I’d still think twice about buying one with ready money though as depreciation is likely to be bad while electric car pricing changes from a premium to a discount.

To underline the significance of all this. Your car battery will easily run a 3kW heat pump over a winter afternoon and evening consuming say 21kW.hrs and delivering 63kW.hrs or more to your heating. A 7kW wall charger will recharge your battery with 28kW.hrs later that night for £2.10. There will be some efficiency losses but the astonishing fact is that solar panels + car + heat pump will slash your energy costs to below 5p when everyone else will be paying 50p odd.

While doing your sums, don’t forget night storage heaters. They store energy more efficiently and cheaply than batteries. Everybody hates this old technology, especially with electricity prices soaring, so you might find some cheap ones on Ebay.

The technology for all of this exists now, heat pumps and electric cars will soon be the norm so many of us will be ready for this anyway. Storing energy makes renewables work better so it makes one wonder if we need to build more nuclear power stations.

Heat pumps update

The renewable heat incentive on heat pumps ended in March 2022. Instead, you can get £5,000 for an ASHP and £6,000 for a GSHP. Your installer makes the claim so you might not actually find all this money in your own pocket. All this leaves a big question over heat pump viability especially with daft quotes from the suppliers.

If you have town gas, why bother? Heat pumps run on electricity that costs 4 times as much as gas.

Gas boilers are cheaper and usually much more powerful and they almost certainly suit your existing system.

In favour though:

If you make your own electricity then a heat pump is a perfect partner.

 A small mini split system (air to air) is about £1,000 and will run free on your panels – it does not qualify for the grant though.

Using surplus electricity to run the immersion heater means you don’t need a new water tank so a heat pump installation will cost less. Knocking say £2,000 off your heat pump quote will buy you some PV panels.

There’s a theme emerging here: Get some panels running before you even think about a heat pump.

Solar car port

A simple car port with some 240v panels must be an early consideration in the energy battle. Cheap to put up, no scaffolding, no roof attachments just useful power and a new useful building. A 4×5 panel layout is likely, so about 7kW and £7,000.   By the way – have you seen postcrete in action? Stick a post  in the hole, pour the dust around it, make sure it’s straight then pour in some water; job done. That car port will be up in no time.

The latest 240v panels, with their own microinverters built in, allow us to make some improvements as they don’t need string matching and we can vary the tilt angles. The highest row can be tilted up slightly without making the car port too high and the lowest row can be tilted down to pick up more winter sun. Assuming you are going to put panels somewhere on your property the car port makes a sensible option. With no rooftop scaffolding costs this is an easy construction with space for as much power as you need and you add value to your property too.

The air cooled roof idea works really well with a PV car port and even more so with my air assisted hybrid ground source heat pump. The hot air under the car port panels is blown down through a string of radiators and that warmed water makes the ground source system work better. See https://wordpress.com/post/originaltwist.com/4622

I was plugging this idea when the incentives were in the order of £20,000 ….. too late now and not worth doing on the reduced payment but an air source heat pump working with the car port makes sense.

Driveable solar annex. The latest energy costs have made it time to review my mad idea for a solar powered driveable house. Apart from being a massive power supply with its sun tracking solar array (makes £2,500+ worth of electricity a year) it can earn over £1,000 a week on AirBnb. The transmission has been made much simpler and easier with regular car parts and the panels now mount on one side – the other side is all sliding glass doors for your viewing pleasure. Catch up here.

Since this drawing further thoughts have made the design even easier. A bespoke container room dropped on a 4×4 chassis makes it all easier and a slab of solar panels across the top help to make an awning over the sun deck. Job done.

Driveable housesliding


Casio LCW-M170TD-1AER Lineage Waveceptor

You might remember me going on about my Casio solar powered and radio timed watch. Some 15 years on with no new batteries or straps it is still ticking on faithfully. However, Casio have made a new watch which has been reviewed as maybe the best watch in the world. I’ve bought one and it’s hard not to agree. Super light, slim and with solar and radio timekeeping. One amusing feature is the second hand. It figures there is no need to tick if you can’t see it, so in the dark it just parks until light returns then it shoots round to find the exact second. The titanium case and strap are a dull grey colour which gives a more grown up, less bling, look to a very understated watch. I love it.